Subject |
Source |
Availability |
Contact information |
---|---|---|---|
Chemoprophylaxis | CDC Traveler's Health internet site (includes online access to Health Information for International Travel] | 24 hours/day | http://wwwnc.cdc.gov/travel |
Health Information for International Travel (Yellow Book) | The latest edition is available for sale from Oxford University Press (https://global.oup.com/academic/?cc=us&lang=en& and from major online booksellers | https://wwwnc.cdc.gov/travel/page/yellowbook-home-2020; 800-445-9714; [email protected]; http://www.oup.com/us | |
CDC Malaria Branch website with malaria and chemoprophylaxis information by country | 24 hours/day | http://www.cdc.gov/malaria/travelers/country_table/a.html | |
Diagnosis | CDC Division of Parasitic Diseases and Malaria diagnostic Internet site (DPDx) | 24 hours/day | https://www.cdc.gov/dpdx/index.html |
CDC Division of Parasitic Diseases and Malaria diagnostic Internet site (DPDx): Bench Aids | 24 hours/day | https://www.cdc.gov/dpdx/diagnosticprocedures/index.html | |
Treatment | CDC malaria treatment guidelines | 24 hours/day | https://www.cdc.gov/malaria/diagnosis_treatment/clinicians1.html |
Clinical advice | CDC Malaria Hotline | 9:00 a.m.–5:00 p.m. Eastern Time, Monday–Friday | 770-488-7788 or 855-856-4713 |
For clinicians and blood banks only | After hours, on weekends, and on holidays | 770-488-7100 | |
Malaria questions | CDC Information | 8:00 a.m.–8:00 p.m. Eastern Time, Monday–Friday | 1-800-CDC-INFO (1-800-232-4636) |
For the general public | 24 hours/day | https://wwwn.cdc.gov/dcs/ContactUs/Form |
Table 1. Resources for malaria chemoprophylaxis, diagnosis, and treatment guidelines
This report summarizes malaria cases reported to CDC with onset of symptoms in 2018, describes trends during previous years, and highlights information on risk factors and prevention. The intended audience includes public health authorities, health care providers, and persons traveling to areas with malaria transmission. Information on chemoprophylaxis, diagnosis, and treatment is provided for health care professionals and the public, and links to additional malaria information and resources are provided.
Year |
U.S. military personnel |
U.S. civilians |
Non-U.S. residents |
Status not recorded |
Total |
---|---|---|---|---|---|
No. (%) |
No. (%) |
No. (%) |
No. (%) |
No. (%) |
|
1970 | 4,096 (96.4) | 90 (2.1) | 44 (1.0) | 17 (0.4) | 4,247 (100) |
1971 | 2,975 (93.6) | 79 (2.5) | 69 (2.2) | 57 (1.8) | 3,180 (100) |
1972 | 454 (73.9) | 106 (17.3) | 54 (8.8) | 0 (0.0) | 614 (100) |
1973 | 41 (18.5) | 103 (46.4) | 78 (35.1) | 0 (0.0) | 222 (100) |
1974 | 21 (6.5) | 158 (48.9) | 144 (44.6) | 0 (0.0) | 323 (100) |
1975 | 17 (3.8) | 199 (44.4) | 232 (51.8) | 0 (0.0) | 448 (100) |
1976 | 5 (1.2) | 178 (42.9) | 227 (54.7) | 5 (1.2) | 415 (100) |
1977 | 11 (2.3) | 233 (48.4) | 237 (49.3) | 0 (0.0) | 481 (100) |
1978 | 31 (5.0) | 270 (43.8) | 315 (51.1) | 0 (0.0) | 616 (100) |
1979 | 11 (1.3) | 229 (26.1) | 634 (72.3) | 3 (0.3) | 877 (100) |
1980 | 26 (1.4) | 303 (16.3) | 1,534 (82.3) | 1 (0.1) | 1,864 (100) |
1981 | 21 (1.9) | 273 (24.8) | 809 (73.3) | 0 (0.0) | 1,103 (100) |
1982 | 8 (0.9) | 348 (37.4) | 574 (61.7) | 0 (0.0) | 930 (100) |
1983 | 10 (1.2) | 325 (40.5) | 468 (58.3) | 0 (0.0) | 803 (100) |
1984 | 24 (2.4) | 360 (35.4) | 632 (62.2) | 0 (0.0) | 1,016 (100) |
1985 | 31 (3.0) | 446 (42.7) | 568 (54.4) | 0 (0.0) | 1,045 (100) |
1986 | 35 (3.2) | 410 (37.6) | 646 (59.2) | 0 (0.0) | 1,091 (100) |
1987 | 23 (2.5) | 421 (45.2) | 488 (52.4) | 0 (0.0) | 932 (100) |
1988 | 33 (3.2) | 550 (53.8) | 440 (43.0) | 0 (0.0) | 1,023 (100) |
1989 | 35 (3.2) | 591 (53.6) | 476 (43.2) | 0 (0.0) | 1,102 (100) |
1990 | 36 (3.3) | 558 (50.8) | 504 (45.9) | 0 (0.0) | 1,098 (100) |
1991 | 22 (2.1) | 585 (55.9) | 439 (42.0) | 0 (0.0) | 1,046 (100) |
1992 | 29 (3.2) | 394 (43.3) | 481 (52.9) | 6 (0.7) | 910 (100) |
1993 | 278 (21.8) | 519 (40.7) | 453 (35.5) | 25 (2.0) | 1,275 (100) |
1994 | 38 (3.7) | 524 (51.7) | 370 (36.5) | 82 (8.1) | 1,014 (100) |
1995 | 12 (1.0) | 599 (51.3) | 461 (39.5) | 95 (8.1) | 1,167 (100) |
1996 | 32 (2.3) | 618 (44.4) | 636 (45.7) | 106 (7.6) | 1,392 (100) |
1997 | 28 (1.8) | 698 (45.2) | 592 (38.3) | 226 (14.6) | 1,544 (100) |
1998 | 22 (1.8) | 636 (51.8) | 361 (29.4) | 208 (17.0) | 1,227 (100) |
1999 | 55 (3.6) | 833 (54.1) | 381 (24.7) | 271 (17.6) | 1,540 (100) |
2000 | 46 (3.3) | 827 (59.0) | 354 (25.2) | 175 (12.5) | 1,402 (100) |
2001 | 18 (1.3) | 891 (64.4) | 316 (22.8) | 158 (11.4) | 1,383 (100) |
2002 | 33 (2.5) | 849 (63.5) | 272 (20.3) | 183 (13.7) | 1,337 (100) |
2003 | 36 (2.8) | 767 (60.0) | 306 (23.9) | 169 (13.2) | 1,278 (100) |
2004 | 32 (2.4) | 775 (58.5) | 282 (21.3) | 235 (17.7) | 1,324 (100) |
2005 | 36 (2.4) | 870 (56.9) | 297 (19.4) | 325 (21.3) | 1,528 (100) |
2006 | 50 (3.2) | 736 (47.1) | 217 (13.9) | 561 (35.9) | 1,564 (100) |
2007 | 33 (2.2) | 701 (46.6) | 263 (17.5) | 508 (33.8) | 1,505 (100) |
2008 | 19 (1.5) | 510 (39.3) | 176 (13.6) | 593 (45.7) | 1,298 (100) |
2009 | 18 (1.2) | 661 (44.5) | 201 (13.5) | 604 (40.7) | 1,484 (100) |
2010 | 46 (2.7) | 1,085 (64.2) | 368 (21.8) | 192 (11.4) | 1,691 (100) |
2011 | 91 (4.7) | 1,098 (57.0) | 386 (20.1) | 350 (18.2) | 1,925 (100) |
2012 | 43 (2.5) | 1,121 (66.4) | 328 (19.4) | 195 (11.6) | 1,687 (100) |
2013 | 14 (0.8) | 1,136 (65.2) | 349 (20.0) | 242 (13.9) | 1,741 (100) |
2014 | 31 (1.8) | 1,114 (64.6) | 384 (22.3) | 196 (11.4) | 1,725 (100) |
2015 | 23 (1.5) | 933 (61.2) | 368 (24.2) | 200 (13.1) | 1,524 (100) |
2016 | 41 (2.0) | 1,216 (58.5) | 581 (28.0) | 240 (11.5) | 2,078 (100) |
2017 | 26 (1.2) | 1,290 (59.7) | 516 (23.9) | 329 (15.2) | 2,161 (100) |
2018 | 38 (2.1)† | 1,066 (58.5) | 375 (20.6)† | 344 (18.9)† | 1,823 (100) |
Table 2. Number of malaria cases* among U.S. military personnel, U.S. civilians, and non-U.S residents — United States, 1970–2018
* A case was defined as symptomatic or asymptomatic illness that occurs in the United States or one of its territories in a person who has laboratory-confirmed malaria parasitemia (microscopy or polymerase chain reaction), regardless of whether the person had previous episodes of malaria. A subsequent episode of malaria occurring in a person is counted as an additional case unless it occurred as a result of a drug resistance failure. Relapsing illnesses are counted as a subsequent case.
† Denotes 2018 values that are statistically different (Pearson’s chi-square, p<0.5) from those in 2017.
Characteristic |
U.S. military personnel |
U.S. civilians |
Non-U.S. residents |
Status not recorded |
Total |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
No. |
(%)* |
(%)† |
No. |
(%)* |
(%)† |
No. |
(%)* |
(%)† |
No. |
(%)* |
(%)† |
No. |
(%)* |
(%)† |
|
Total | 38 | (2.1) | —§ | 1,066 | (58.5) | —§ | 375 | (20.6) | —§ | 344 | (18.9) | —§ | 1,826 | (100) | —§ |
Sex | |||||||||||||||
Male | 36 | (94.7) | —¶ | 671 | (63.0) | —¶ | 214 | (57.1) | (57.2) | 205 | (59.6) | (61.9) | 1,126 | (61.8) | (62.2) |
Female | 2 | (5.3) | —¶ | 395 | (37.1) | —¶ | 160 | (42.7) | (42.8) | 126 | (36.6) | (38.1) | 638 | (37.5) | (37.8) |
Unknown | 0 | (0.0) | —¶,** | 0 | (0.0) | —¶,** | 1 | (0.3) | —** | 13 | (3.8) | —** | 14 | (0.8) | —** |
Age (yrs) | |||||||||||||||
<18
|
0
|
(0.0) | —†† | 131 | (12.3) | —†† | 130 | (34.7) | —†† | 33 | (9.6) | —†† | 294 | (16.1) | —†† |
18–64 | 38 | (100) | —†† | 840 | (78.8) | —†† | 225 | (60.0) | —†† | 294 | (85.5) | —†† | 1,397 | (76.6) | —†† |
≥65 | 0 | (0.0) | —†† | 95 | (8.9) | —†† | 20 | (5.3) | —†† | 17 | (4.9) | —†† | 132 | (7.2) | —†† |
Race and ethnicity | |||||||||||||||
Ethnicity | |||||||||||||||
Not Hispanic or Latino | 16 | (42.1) | (76.2) | 835 | (78.3) | (97.3) | 296 | (78.9) | (97.4) | 209 | (60.8) | (100.0) | 1,356 | (74.4) | (97.4) |
Hispanic or Latino | 5 | (13.2) | (23.8) | 23 | (2.2) | (2.7) | 8 | (2.1) | (2.6) | 0 | (0.0) | (0.0) | 36 | (2.0) | (2.6) |
Unknown | 17 | (44.7) | —** | 2.8 | (19.5) | —** | 71 | (18.9) | —** | 135 | (39.2) | —** | 431 | (23.6) | —** |
Race | |||||||||||||||
Asian | 0 | (0.0) | (0.0) | 31 | (2.9) | (3.2) | 39 | (10.4) | (11.5) | 41 | (11.9) | (15.7) | 111 | (6.1) | (3.9) |
Black or African American | 11 | (29.0) | (33.3) | 769 | (72.2) | (78.8) | 265 | (70.7) | (78.4) | 179 | (51.9) | (68.3) | 1,224 | (67.1) | (76.1) |
White | 20 | (56.2) | (60.6) | 134 | (12.6) | (13.7) | 17 | (4.5) | (5.0) | 33 | (9.6) | (12.6) | 204 | (11.2) | (12.7) |
Other§§ | 2 | (5.3) | (6.1) | 42 | (3.9) | (4.3) | 17 | (4.5) | (5.0) | 9 | (2.6) | (3.4) | 70 | (3.8) | (4.4) |
Unknown | 5 | (18.4) | —** | 90 | (12.3) | —** | 37 | (14.4) | —** | 82 | (26.7) | —** | 214 | (15.6) | —** |
Region of acquisition¶¶ | |||||||||||||||
Africa | 12 | (31.6) | (32.4) | 970 | (91.3) | (92.3) | 304 | (81.1) | (81.7) | 233 | (81.1) | (88.9) | 1,519 | (85.0 | (88.2) |
West Africa, unspecified | 5 | (13.5) | (13.5) | 713 | (67.0) | (67.8) | 170 | (45.3) | (45.7) | 173 | (55.6) | (66.0) | 1,061 | (59.3) | (61.6) |
Asia | 25 | (65.8) | (67.6) | 41 | (3.9) | (3.9) | 54 | (14.4) | (14.5) | 21 | (6.8) | (8.0) | 141 | (7.9) | (8.2) |
South America | 0 | (0.0) | (0.0) | 16 | (1.5) | (1.5) | 12 | (3.2) | (3.2) | 7 | (2.7) | (2.7) | 35 | (2.0) | (2.0) |
Central America or the Caribbean | 0 | (0.0) | (0.0) | 19 | (1.8) | (1.8) | 2 | (0.5) | (0.5) | 0 | (0.0) | (0.0) | 21 | (1.2) | (1.2) |
Oceania | 0 | (0.0) | (0.0) | 5 | (0.5) | (0.5) | 0 | (0.0) | (0.0) | 1 | (0.3) | (0.4) | 6 | (0.3) | (0.4) |
Unknown | 1 | (2.3) | —** | 13 | (1.2) | —** | 3 | (0.8) | —** | 49 | (15.7) | —** | 66 | (3.7) | —** |
Total | 38 | (100) | (100) | 1,064 | (100) | (100) | 375 | (100) | (100) | 311 | (100) | (100) | 1,788 | (100) | (100) |
Primary reason for travel¶¶ | |||||||||||||||
Visiting friends and relatives | 4 | (10.5) | (10.5) | 673 | (63.3) | (77) | 82 | (21.9) | (26.0) | 74 | (23.7) | (71.8) | 833 | (46.6) | (62.6) |
Tourist | 0 | (0) | (0) | 71 | (6.7) | (8.1) | 6 | (1.6) | (1.9) | 9 | (2.9) | (8.7) | 86 | (4.8) | (6.5) |
Missionary or dependent | 0 | (0) | (0) | 45 | (4.2) | (5.2) | 5 | (1.3) | (1.6) | 5 | (1.6) | (4.9) | 55 | (3.1) | (4.1) |
Business | 0 | (0) | (0) | 61 | (5.7) | (7.0) | 14 | (3.7) | (4.4) | 6 | (1.9) | (5.8) | 81 | (4.5) | (6.1) |
Student or teacher | 0 | (0) | (0) | 20 | (1.9) | (2.3) | 15 | (4.0) | (4.8) | 7 | (2.2) | (6.8 | 42 | (2.4) | (3.1) |
Air crew or sailor | 0 | (0) | (0) | 1 | (0.1) | (0.1) | 3 | (0.8) | (1.0) | 0 | (0) | (0) | 4 | (0.2) | (0.3) |
Peace Corps | 0 | (0) | (0) | 1 | (0.1) | (0.1) | 0 | (0) | (0) | 0 | (0) | (0) | 1 | (0.1) | (0.1) |
Refugee or immigrant | 0 | (0) | (0) | 0 | (0) | (0) | 183 | (40.8) | (58.1) | 0 | (0) | (0) | 183 | (10.2) | (13.8) |
Military deployment | 34 | (89.5) | (89.5) | 0 | (0) | (0) | 2 | (0.5) | (0.6) | 0 | (0) | (0) | 36 | (2.0) | (2.7) |
Other | 0 | (0) | (0) | 2 | (0.2) | (0.2) | 5 | (1.3) | (1.6) | 2 | (0.6) | (1.9) | 9 | (0.5) | (0.7) |
Unknown | 0 | (0) | —** | 190 | (19.9 | —** | 60 | (16) | —** | 208 | (66.7) | —** | 458 | (25.6) | —** |
Total | 38 | (100) | (100) | 1,064 | (100) | (100) | 375 | (100) | (100) | 311 | (100) | (100) | 1,788 | (100) | (100) |
Table 3. Number of malaria cases by demographics, region of acquisition, and primary reason for travel, by subject resident status — United States, 2018
* Percentage calculated among all subjects.
† Percentage calculated among subjects with known responses.
§ Not applicable because all cases were categorized by resident status.
¶ Not applicable because sex was known for all subjects.
** Not applicable because unknown responses were excluded from the calculation.
†† Not applicable because age was known for all subjects.
§§ Other race includes American Indian or Alaska Native, Native Hawaiian or Pacific Islander, mixed race, or another race not specified.
¶¶ Among imported cases.
Species |
2014 |
2015 |
2016 |
2017 |
2018 |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
No. |
(%)* |
(%)† |
No. |
(%)* |
(%)† |
No. |
(%)* |
(%)† |
No. |
(%)* |
(%)† |
No. |
(%)* |
(%)† |
|
P. falciparum | 1,141 | (66.1) | (74.9) | 1,025 | (67.3) | (77.2) | 1,419 | (68.3) | (76.6) | 1,523 | (70.5) | (78.7) | 1,273 | (69.8) | (79.2) |
P. vivax | 230 | (13.3) | (15.1) | 180 | (11.8) | (13.6) | 251 | (12.1) | (13.6) | 216 | (10) | (11.2) | 173 | (9.5) | (10.8) |
P. ovale | 90 | (5.2) | (5.9) | 63 | (4.1) | (4.7) | 99 | (4.8) | (5.3) | 119 | (5.5) | (6.2) | 95 | (5.2) | (5.9) |
P. malariae | 47 | (2.7) | (3.1) | 48 | (3.2) | (3.6) | 61 | (2.9) | (3.3) | 55 | (2.6) | (2.8) | 48 | (2.6) | (3) |
P. knowlesi | 0 | (0) | (0) | 0 | (0) | (0) | 0 | (0) | (0) | 0 | (0) | (0) | 1 | (0.1) | (0.1) |
Mixed | 15 | (0.9) | (1) | 12 | (0.8) | (0.9) | 23 | (1.1) | (1.2) | 22 | (1) | (1.1) | 17 | (0.9) | (1.1) |
Undetermined | 202 | (11.7) | —§ | 196 | (12.9) | — | 225 | (10.8) | — | 226 | (10.5) | — | 216 | (11.9) | — |
Total | 1,725 | (100) | (100) | 1,524 | (100) | (100) | 2,078 | (100) | (100) | 2,161 | (100) | (100) | 1,823 | (100) | (100) |
Table 4. Number of malaria cases, by Plasmodium species and year — United States, 2014–2018
* Percentage among all infections.
† Percentage among infections with known species.
§ Not applicable because undetermined species were excluded from the calculation.
Country of acquisition |
P. falciparum |
P. vivax |
P. ovale |
P. malariae |
P. knowlesi |
Mixed |
Unknown |
Total |
||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
PCR |
Total |
PCR |
Total |
PCR |
Total |
PCR |
Total |
PCR |
Total |
PCR |
Total |
PCR |
Total |
PCR |
Total |
|
Africa | 518 | 1,217 | 8 | 31 | 46 | 86 | 23 | 43 | 0 | 0 | 11 | 14 | 11 | 128 | 617 | 1,519 |
Angola | 2 | 7 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 2 | 9 |
Benin | 1 | 4 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 4 |
Burkina Faso | 8 | 13 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 8 | 14 |
Burundi | 3 | 4 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 4 |
Cameroon | 26 | 80 | 0 | 3 | 3 | 3 | 0 | 5 | 0 | 0 | 3 | 3 | 0 | 9 | 32 | 103 |
Central African Republic | 0 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 3 |
Chad | 4 | 7 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 5 | 9 |
Congo, Democratic Republic of | 11 | 24 | 0 | 1 | 2 | 3 | 2 | 2 | 0 | 0 | 0 | 0 | 2 | 7 | 17 | 37 |
Equatorial Guinea | 1 | 6 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 7 |
Ethiopia | 3 | 6 | 3 | 11 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 6 | 18 |
Gabon | 2 | 7 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 8 |
Gambia, The | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Ghana | 63 | 114 | 1 | 3 | 3 | 5 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 10 | 68 | 132 |
Guinea | 37 | 54 | 0 | 0 | 2 | 2 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 40 | 57 |
Guinea-Bissau | 1 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 2 |
Ivory Coast | 38 | 64 | 0 | 0 | 1 | 3 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 9 | 41 | 78 |
Kenya | 20 | 51 | 0 | 0 | 0 | 0 | 2 | 3 | 0 | 0 | 0 | 0 | 1 | 3 | 23 | 57 |
Liberia | 39 | 104 | 0 | 0 | 0 | 3 | 1 | 2 | 0 | 0 | 0 | 0 | 1 | 13 | 41 | 122 |
Malawi | 0 | 2 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 3 |
Mali | 7 | 13 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 8 | 15 |
Mozambique | 0 | 2 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 4 |
Niger | 1 | 6 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 6 |
Nigeria | 137 | 316 | 1 | 3 | 18 | 36 | 5 | 8 | 0 | 0 | 2 | 2 | 4 | 37 | 167 | 402 |
Rwanda | 2 | 4 | 1 | 1 | 0 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 8 |
Senegal | 2 | 3 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 4 |
Sierra Leone | 36 | 130 | 0 | 1 | 2 | 3 | 0 | 2 | 0 | 0 | 1 | 2 | 0 | 14 | 39 | 152 |
South Africa | 1 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 3 |
South Sudan | 2 | 10 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 12 |
Sudan | 9 | 28 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 10 | 32 |
Tanzania | 8 | 19 | 0 | 0 | 6 | 8 | 1 | 2 | 0 | 0 | 3 | 3 | 1 | 3 | 19 | 35 |
Togo | 19 | 38 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 20 | 40 |
Uganda | 11 | 27 | 1 | 2 | 3 | 5 | 3 | 6 | 0 | 0 | 0 | 1 | 0 | 2 | 18 | 43 |
Zambia | 2 | 4 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 2 | 5 |
Zimbabwe | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 |
Africa, unspecified | 6 | 27 | 0 | 0 | 2 | 3 | 1 | 2 | 0 | 0 | 0 | 1 | 0 | 2 | 9 | 35 |
Central Africa, unspecified | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
East Africa, unspecified | 3 | 8 | 0 | 3 | 1 | 2 | 1 | 3 | 0 | 0 | 0 | 0 | 0 | 3 | 5 | 19 |
South Africa, unspecified | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 2 |
West Africa, unspecified | 12 | 25 | 0 | 0 | 0 | 2 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 4 | 14 | 32 |
Asia | 4 | 12 | 40 | 103 | 1 | 4 | 1 | 4 | 1 | 1 | 0 | 0 | 0 | 17 | 47 | 141 |
Afghanistan | 0 | 2 | 18 | 43 | 0 | 2 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 5 | 18 | 53 |
Cambodia | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
India | 2 | 6 | 15 | 36 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 10 | 17 | 53 |
Indonesia | 1 | 2 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 3 |
Laos | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 |
Pakistan | 0 | 0 | 5 | 13 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 5 | 16 |
Philippines | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 2 | 2 |
South Korea | 0 | 0 | 0 | 6 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 6 |
Thailand | 1 | 1 | 1 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 4 |
Vietnam | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Southeast Asia, unspecified | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Central America and the Caribbean | 5 | 8 | 0 | 10 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 5 | 21 |
Dominican Republic | 2 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 3 |
Guatemala | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
Haiti | 3 | 5 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 3 | 6 |
Honduras | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Nicaragua | 0 | 0 | 0 | 6 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 7 |
Panama | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Central America, unspecified | 0 | 0 | 0 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 |
South America | 0 | 2 | 11 | 23 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 2 | 0 | 8 | 13 | 35 |
Brazil | 0 | 0 | 1 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 3 |
Colombia | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
Guyana | 0 | 0 | 7 | 9 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 2 | 0 | 0 | 9 | 11 |
Peru | 0 | 2 | 1 | 4 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 6 | 1 | 12 |
Venezuela | 0 | 0 | 2 | 6 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 6 |
South America, unspecified | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 2 |
Oceania | 3 | 3 | 2 | 2 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 5 | 6 |
Papua New Guinea | 3 | 3 | 2 | 2 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 5 | 6 |
Unknown | 2 | 13 | 1 | 3 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 48 | 5 | 66 |
Total | 532 | 1,255 | 62 | 172 | 48 | 91 | 24 | 48 | 1 | 1 | 14 | 17 | 11 | 204 | 692 | 1,788 |
Table 5. Number of imported malaria cases (including polymerase chain reaction-confirmed cases), by country of acquisition and Plasmodium species — United States, 2018
Abbreviation: PCR = polymerase chain reaction.
Interval (days) |
P. falciparum No. (%) |
P. vivax No. (%) |
P. ovale No. (%) |
P. malariae No. (%) |
Mixed No. (%) |
Total No. (%) |
---|---|---|---|---|---|---|
<0† | 153 (15.2) | 11 (8.8) | 6 (9.4) | 2 (6.1) | 1 (8.3) | 173 (14.0) |
0–29 | 799 (79.6) | 41 (32.8) | 22 (34.4) | 20 (60.6) | 8 (66.7) | 890 (71.9) |
30–89 | 42 (4.2) | 22 (17.6) | 10 (15.6) | 7 (21.2) | 2 (16.7) | 83 (6.7) |
90–179 | 5 (0.5) | 17 (13.6) | 7 (10.9) | 3 (9.1) | 1 (8.3) | 33 (2.7) |
180–364 | 3 (0.3) | 26 (20.8) | 15 (23.4) | 1 (3.0) | 0 (0) | 45 (3.6) |
≥365 | 2 (0.2) | 8 (6.4) | 4 (6.3) | 0 (0) | 0 (0) | 14 (1.1) |
Total | 1,004 (100.0) | 125 (100.0) | 64 (100.0) | 33 (100.0) | 12 (100.0) | 1,238 (100.0) |
Table 6. Number and percentage of imported malaria cases, by Plasmodium species* and interval between date of arrival in the United States and onset of illness — United States, 2018
* This table does not include one case of P. knowlesi because of incomplete travel dates. Persons for whom Plasmodium species, date of arrival in the United States, or date of onset of illness is unknown are not included.
† Cases in this row are among patients who had onset of illness before arriving in the United States.
Category |
Region) |
||||||
---|---|---|---|---|---|---|---|
Africa No. (%) |
Asia No. (%) |
South America No. (%) |
Central America and the Caribbean No. (%) |
Oceania No. (%) |
Total No. (%) |
||
Visiting friends and relatives | 776 (66.7) | 36 (30.8) | 7 (31.8) | 9 (56.3) | 0 (0) | 828 (62.7) | |
Tourist | 66 (5.7) | 10 (8.9) | 7 (31.8) | 3 (18.8) | 0 (0) | 86 (6.5) | |
Missionary or dependent | 48 (4.1) | 1 (0.9) | 2 (9.1) | 2 (12.5) | 1 (33.3) | 54 (4.1) | |
Business | 70 (6) | 3 (2.6) | 5 (22.7) | 1 (6.3) | 2 (66.7) | 81 (6.1) | |
Student or teacher | 41 (3.5) | 0 (0) | 1 (4.6) | 0 (0) | 0 (0) | 42 (3.2) | |
Air crew or sailor | 1 (0.1) | 3 (2.6) | 0 (0) | 0 (0) | 0 (0) | 4 (0.3) | |
Peace Corps | 0 (0) | 1 (0.9) | 0 (0) | 0 (0) | 0 (0) | 1 (0.1) | |
Refugee or immigrant | 143 (12.3) | 37 (31.6) | 0 (0) | 1 (6.3) | 0 (0) | 181 (13.7) | |
Military deployment | 9 (0.8) | 26 (22.2) | 0 (0) | 0 (0) | 0 (0) | 35 (2.7) | |
Other | 9 (0.8) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 9 (0.7) | |
Total | 1,163 (100) | 117 (100) | 22 (100) | 16 (100) | 3 (100) | 1,321 (100) |
Table 7. Number and percentage of imported cases among U.S. military personnel, U.S. civilians, and non-U.S residents, by purpose of travel at the time of malaria acquisition – United States, 2018
Resistance markers |
Region) |
|||
---|---|---|---|---|
Africa No. (%) |
Asia No. (%) |
Unknown* No. (%) |
Total No. (%) |
|
Pyrimethamine | 98 (97.0) | 1 (1.0) | 2 (2.0) | 101 (100) |
No resistance markers | 2 (2.0) | 0 (0) | 0 (0) | 2 (2.0) |
1 resistance marker | 0 (0) | 0 (0) | 0 (0) | 0 (0) |
2 resistance markers | 5 (5.0) | 1 (1.0) | 0 (0) | 6 (5.9) |
3 or more resistance markers | 91 (90.1) | 0 (0) | 2 (2.0) | 93 (92.1) |
Sulfadoxine | 100 (97.1) | 1 (1.0) | 2 (1.9) | 103 (100) |
No resistance markers | 52 (50.5) | 1 (1.0) | 1 (1.0) | 54 (52.4) |
1 resistance marker | 26 (25.2) | 0 (0) | 1 (1.0) | 27 (26.2) |
2 resistance markers | 15 (14.6) | 0 (0) | 0 (0) | 15 (14.6) |
3 or more resistance markers | 7 (6.8) | 0 (0) | 0 (0) | 7 (6.8) |
Chloroquine | 107 (97.3) | 1 (0.9) | 2 (1.8) | 110 (100) |
No resistance markers | 58 (52.7) | 0 (0) | 2 (1.8) | 60 (54.5) |
1 resistance marker | 0 (0) | 0 (0) | 0 (0) | 0 (0) |
2 resistance markers | 0 (0) | 1 (0.9) | 0 (0) | 1 (0.9) |
3 resistance markers | 49 (44.6) | 0 (0) | 0 (0) | 49 (44.5) |
Mefloquine | 97 (98.0) | 1 (1.0) | 1 (1.0) | 99 (100) |
No resistance markers | 95 (96.0) | 1 (1.0) | 1 (1.0) | 97 (98.0) |
1 resistance marker | 2 (2.0) | 0 (0) | 0 (0) | 2 (2.0) |
Atovaquone | 94 (97.9) | 1 (1.0) | 1 (1.0) | 96 (100) |
No resistance markers | 94 (97.9) | 1 (1.0) | 1 (1.0) | 96 (100) |
Artemisinin | 107 (97.3) | 1 (0.9) | 2 (1.8) | 110 (100) |
No resistance markers | 107 (97.3) | 1 (0.9) | 2 (1.8) | 110 (100) |
Table 8. Antimalarial drug resistance marker results among Plasmodium falciparum specimens, by drug and region of malaria acquisition — United States, 2018
* There were no specimens for molecular resistance marker analysis acquired from South America, Central America and the Caribbean, or Oceania.
Physicians - maximum of 1.25 AMA PRA Category 1 Credit(s)™
ABIM Diplomates - maximum of 1.25 ABIM MOC points
Nurses - 1.25 ANCC Contact Hour(s) (0.5 contact hours are in the area of pharmacology)
Pharmacists - 1.25 Knowledge-based ACPE (0.125 CEUs)
This activity is intended for public health officials, infectious disease clinicians, tropical medicine clinicians, internists, and other clinicians caring for patients with or at risk for malaria.
The goal of this activity is for learners to be better able to describe malaria surveillance in the United States and its territories, based on a Centers for Disease Control and Prevention (CDC) report of confirmed malaria cases in persons with onset of illness in 2018 and trends in previous years that summarizes data from integration of all cases from the National Malaria Surveillance System, the National Notifiable Diseases Surveillance System, CDC clinical consultations, and CDC reference laboratory reports.
Upon completion of this activity, participants will:
Medscape, LLC requires every individual in a position to control educational content to disclose all financial relationships with ineligible companies that have occurred within the past 24 months. Ineligible companies are organizations whose primary business is producing, marketing, selling, re-selling, or distributing healthcare products used by or on patients.
All relevant financial relationships for anyone with the ability to control the content of this educational activity are listed below and have been mitigated. Others involved in the planning of this activity have no relevant financial relationships.
Medscape, LLC designates this enduring material for a maximum of 1.25
AMA PRA Category 1 Credit(s)™
. Physicians should claim only the credit commensurate with the extent of their participation in the activity.
Successful completion of this CME activity, which includes participation in the evaluation component, enables the participant to earn up to 1.25 MOC points in the American Board of Internal Medicine's (ABIM) Maintenance of Certification (MOC) program. Participants will earn MOC points equivalent to the amount of CME credits claimed for the activity. It is the CME activity provider's responsibility to submit participant completion information to ACCME for the purpose of granting ABIM MOC credit.
Awarded 1.25 contact hour(s) of nursing continuing professional development for RNs and APNs; 0.50 contact hours are in the area of pharmacology.
Medscape designates this continuing education activity for 1.25 contact hour(s) (0.125 CEUs) (Universal Activity Number: JA0007105-0000-23-055-H01-P).
For questions regarding the content of this activity, contact the accredited provider for this CME/CE activity noted above. For technical assistance, contact [email protected]
There are no fees for participating in or receiving credit for this online educational activity. For information on applicability
and acceptance of continuing education credit for this activity, please consult your professional licensing board.
This activity is designed to be completed within the time designated on the title page; physicians should claim only those
credits that reflect the time actually spent in the activity. To successfully earn credit, participants must complete the
activity online during the valid credit period that is noted on the title page. To receive AMA PRA Category 1 Credit™, you must receive a minimum score of 70% on the post-test.
Follow these steps to earn CME/CE credit*:
You may now view or print the certificate from your CME/CE Tracker. You may print the certificate, but you cannot alter it.
Credits will be tallied in your CME/CE Tracker and archived for 6 years; at any point within this time period, you can print
out the tally as well as the certificates from the CME/CE Tracker.
*The credit that you receive is based on your user profile.
CME / ABIM MOC / CE Released: 2/17/2023
Valid for credit through: 2/17/2024, 11:59 PM EST
processing....
Note: It is Medscape's policy to avoid the use of brand names in accredited activities. However, in an effort to be as clear as possible, brand names are used in this activity for clarity. The use of brand names should not be viewed as an endorsement of specific products.
Problem/Condition: Malaria in humans is caused by intraerythrocytic protozoa of the genus Plasmodium. These parasites are transmitted by the bite of an infective female Anopheles species mosquito. Most malaria infections in the United States and its territories occur among persons who have traveled to regions with ongoing malaria transmission. However, among persons who have not traveled out of the country, malaria is occasionally acquired through exposure to infected blood or tissues, congenital transmission, nosocomial exposure, or local mosquitoborne transmission. Malaria surveillance in the United States and its territories provides information on its occurrence (e.g., temporal, geographic, and demographic), guides prevention and treatment recommendations for travelers and patients, and facilitates rapid transmission control measures if locally acquired cases are identified.
Period Covered: This report summarizes confirmed malaria cases in persons with onset of illness in 2018 and trends in previous years.
Description of System: Malaria cases diagnosed by blood smear microscopy, polymerase chain reaction, or rapid diagnostic tests are reported to local and state health departments through electronic laboratory reports or by health care providers or laboratory staff members directly reporting to CDC or health departments. Case investigations are conducted by local and state health departments, and reports are transmitted to CDC through the National Malaria Surveillance System (NMSS), the National Notifiable Diseases Surveillance System (NNDSS), or direct CDC clinical consultations. CDC reference laboratories provide diagnostic assistance and conduct antimalarial drug resistance marker testing on blood specimens submitted by health care providers or local or state health departments. This report summarizes data from the integration of all cases from NMSS and NNDSS, CDC clinical consultations, and CDC reference laboratory reports.
Results: CDC received reports of 1,823 confirmed malaria cases with onset of symptoms in 2018, including one cryptic case and one case acquired through a bone marrow transplant. The number of cases reported in 2018 is 15.6% fewer than in 2017. The number of cases diagnosed in the United States and its territories has been increasing since the mid-1970s; the number of cases reported in 2017 was the highest since 1972. Of the cases in 2018, a total of 1,519 (85.0%) were imported cases that originated from Africa; 1,061 (69.9%) of the cases from Africa were from West Africa, a similar proportion to what was observed in 2017. Among all cases, P. falciparum accounted for most infections (1,273 [69.8%]), followed by P. vivax (173 [9.5%]), P. ovale (95 [5.2%]), and P. malariae (48 [2.6%]). For the first time since 2008, an imported case of P. knowlesi was identified in the United States and its territories. Infections by two or more species accounted for 17 cases (<1.0%). The infecting species was not reported or was undetermined in 216 cases (11.9%). Most patients (92.6%) had symptom onset <90 days after returning to the United States or its territories from a country with malaria transmission. Of the U.S. civilian patients who reported reason for travel, 77.0% were visiting friends and relatives. Chemoprophylaxis with antimalarial medications are recommended for U.S. residents to prevent malaria while traveling in countries where it is endemic. Fewer U.S. residents with imported malaria reported taking any malaria chemoprophylaxis in 2018 (24.5%) than in 2017 (28.4%), and adherence was poor among those who took chemoprophylaxis. Among the 864 U.S. residents with malaria for whom information on chemoprophylaxis use and travel region were known, 95.0% did not adhere to or did not take a CDC-recommended chemoprophylaxis regimen. Among 683 women with malaria, 19 reported being pregnant. Of these, 11 pregnant women were U.S. residents, and one of whom reported taking chemoprophylaxis to prevent malaria but her adherence to chemoprophylaxis was not reported. Thirty-eight (2.1%) malaria cases occurred among U.S. military personnel in 2018, more than in 2017 (26 [1.2%]). Among all reported malaria cases in 2018, a total of 251 (13.8%) were classified as severe malaria illness, and seven persons died from malaria. In 2018, CDC analyzed 106 P. falciparum-positive and four P. falciparum mixed species specimens for antimalarial resistance markers (although certain loci were untestable in some specimens); identification of genetic polymorphisms associated with resistance to pyrimethamine were found in 99 (98.0%), to sulfadoxine in 49 (49.6%), to chloroquine in 50 (45.5%), and to mefloquine in two (2.0%); no specimens tested contained a marker for atovaquone or artemisinin resistance.
Interpretation: The importation of malaria reflects the overall trends in global travel to and from areas where malaria is endemic, and 15.6% fewer cases were imported in 2018 compared with 2017. Of imported cases, 59.3% were among persons who had traveled from West Africa. Among U.S. civilians, visiting friends and relatives was the most common reason for travel (77.1%).
Public Health Actions: The best way for U.S. residents to prevent malaria is to take chemoprophylaxis medication before, during, and after travel to a country where malaria is endemic. Adherence to recommended malaria prevention strategies among U.S. travelers would reduce the number of imported cases. Reported reasons for nonadherence include prematurely stopping after leaving the area where malaria was endemic, forgetting to take the medication, and experiencing a side effect. Health care providers can make travelers aware of the risks posed by malaria and incorporate education to motivate them to be adherent to chemoprophylaxis. Malaria infections can be fatal if not diagnosed and treated promptly with antimalarial medications appropriate for the patient’s age, pregnancy status, medical history, the likely country of malaria acquisition, and previous use of antimalarial chemoprophylaxis. Antimalarial use for chemoprophylaxis and treatment should be determined by the CDC guidelines, which are frequently updated. In April 2019, intravenous (IV) artesunate became the first-line medication for treatment of severe malaria in the United States and its territories. Artesunate was approved by the Food and Drug Administration (FDA) in 2020 and is commercially available (Artesunate for Injection) from major U.S. drug distributors (https://amivas.com). Stocking IV artesunate locally allows for immediate treatment of severe malaria once diagnosed and provides patients with the best chance of a complete recovery and no sequelae. With commercial IV artesunate now available, CDC will discontinue distribution of non–FDA-approved IV artesunate under an investigational new drug protocol on September 30, 2022. Detailed recommendations for preventing malaria are online at https://www.cdc.gov/malaria/travelers/drugs.html. Malaria diagnosis and treatment recommendations are also available online at https://www.cdc.gov/malaria/diagnosis_treatment. Health care providers who have sought urgent infectious disease consultation and require additional assistance on diagnosis and treatment of malaria can call the Malaria Hotline 9:00 a.m.–5:00 p.m. Eastern Time, Monday–Friday, at 770-488-7788 or 855-856-4713 or after hours for urgent inquiries at 770-488-7100. Persons submitting malaria case reports (care providers, laboratories, and state and local public health officials) should provide complete information because incomplete reporting compromises case investigations and public health efforts to prevent future infections and examine trends in malaria cases. Molecular surveillance of antimalarial drug resistance markers enables CDC to track, guide treatment, and manage drug resistance in malaria parasites both domestically and globally. A greater proportion of specimens from domestic malaria cases are needed to improve the completeness of antimalarial drug resistance analysis; therefore, CDC requests that blood specimens be submitted for any case of malaria diagnosed in the United States and its territories.
Malaria, a febrile parasitic illness transmitted through the bite of an infective mosquito, was estimated to cause 241 million illnesses in 2020 and 627,000 deaths worldwide[1]. In 2018, there were an estimated 228 million cases of malaria, globally, and 405,000 deaths[2]. Malaria is transmitted in 85 countries, and approximately one half of the world population is at risk for infection[1]. Since 2000, the global community has funded and implemented malaria control efforts and achieved an estimated 23 million fewer malaria cases in 2018 alone, compared with 2010, and cumulatively, these efforts have prevented millions of malaria deaths. However, during 2014–2018, the number of cases globally was stable[2], and in 2020 the number of malaria cases increased compared with previous years, in part because of disruption of health services and interventions from the COVID-19 pandemic[1]. In October 2021, the first malaria vaccine was recommended by the World Health Organization to protect infants and children aged 5–24 months living in moderate-to-high transmission areas[3].
Plasmodium parasites that cause malaria are transmitted through the bite of an infective Anopheles mosquito, resulting in an intraerythrocytic illness, which can range from asymptomatic or mild to severe and fatal. Four species of Plasmodium cause illness in humans: P. falciparum, P. vivax, P. ovale species (caused by P. ovale curtisi and P. ovale wallikeri], and P. malariae. Simian malarias can also cause illness in humans, particularly P. knowlesi in Southeast Asia. P. falciparum causes the most infections worldwide; it is predominant in Africa where an estimated 95% of cases occur[1,2], and partly because of a rapid replication rate, infections from this species can rapidly progress to severe illness, especially for infants and children aged <5 years and among persons who do not have acquired immunity[4]. In 2018, P. vivax accounted for approximately 3% of cases worldwide. P. vivax is found in a broad geographical area and although it contributed <1% of cases in Africa, it made up 75% of cases in the Americas, 50% of cases in Asia, and approximately 30%–35% of cases in the Eastern Mediterranean and Western Pacific regions[2]. Compared with P. vivax and P. falciparum, transmissions of P. ovale spp., P. malariae and P. knowlesi species are limited. Approximately 95% of P. ovale spp. cases were identified in Africa, with 5% in Asia[5]. P. vivax and P. ovale parasites have a dormant stage (hypnozoite) in the liver, making relapse common during the period of 45 days to 3 years after an initial illness[4]. P. vivax parasites transmitted in some areas of Asia can have a long incubation period, lasting 6 or more months from inoculation to symptom onset[6–8]. P. malariae parasites are found throughout the tropics and subtropics and are often detected in mixed species infections. P. malariae parasites mature slowly in human and mosquito hosts and, although they do not typically cause severe symptoms in humans, can result in persistent low-density infections that can last for years, providing opportunities for ongoing transmission and health sequelae[4,9]. P. knowlesi is predominantly a simian malaria found in Southeast Asia; however, it can be transmitted to persons, and in Malaysia, it has become the predominant species that causes malaria illness in humans[10–12]. Exposure to forested areas with simian habitat is a risk factor for P. knowlesi, and these infections can be serious or fatal[10,13].
Although malaria was eliminated from the United States* in the mid-1950s[14], the Anopheles mosquito vector still exists throughout the United States[15]. Since 1957, malaria surveillance has been supported to detect cases and prevent reintroduction, monitor antimalarial resistance, assess trends in case acquisition, and guide malaria prevention and treatment recommendations for U.S. residents. Most malaria cases diagnosed in the United States are imported from countries with ongoing mosquitoborne transmission. Occasionally, congenitally acquired cases, induced cases (resulting from exposure to blood or tissue products), and cryptic cases (for which exposure cannot be easily explained despite investigation by state and local health departments and CDC) occur. During 1957–2003, a total of 63 malaria outbreaks occurred in the United States. The last well-documented local mosquitoborne transmission occurred in 2003, when eight cases were diagnosed among nontravelers in Palm Beach, Florida[16–18].
Clinical illness results from the presence of an asexual, intraerythrocytic stage of the parasite in red blood cells. Factors that contribute to variability in illness severity are complex and include the parasite species and density of infection, the patient’s age and immune response to the infection, the presence of acquired or protective immunity, the patient’s general health and nutritional constitution, chemoprophylaxis effects, and time to initiate appropriate treatment[4]. Persons that live in areas with high malaria transmission who experience repeated malarial illnesses might develop partial protective immunity that can result in less severe illness or even asymptomatic parasitemia. However, without continual exposure, this semi-immunity will be lost within a few years[19–21], and thus it is assumed that U.S. residents do not have any degree of protective immunity to malaria and are susceptible to severe illness and death. Although malaria symptoms vary by age and immunologic status, fever is the predominant symptom[22]. Symptoms associated with uncomplicated malaria include chills, sweating, headache, fatigue, myalgia, cough, nausea, and mild anemia. If not treated promptly, malaria can rapidly progress and affect multiple organ systems and result in altered consciousness (cerebral malaria), seizures, severe anemia, acute kidney injury, liver failure, respiratory distress, coma, permanent disability, and death. Travel history should be routinely requested for patients with fever. All persons who have fever and who recently traveled to areas where malaria is endemic as well as persons who have unexplained fever, regardless of travel history, should be tested immediately for malaria.
To prevent malaria, CDC recommends that U.S. residents use chemoprophylaxis (i.e., antimalarial medication taken before, during, and after travel to a country with malaria transmission). Persons who intend to travel should ask their physician for a prescription for an antimalarial that is appropriate for the country or region of travel, the age of the patient, pregnancy status, and individual preferences (e.g., cost or regimen type [daily versus weekly]). CDC provides chemoprophylaxis guidelines to health care providers and the public (Table 1). Implementing mosquito avoidance measures provides additional protection and includes the use of repellents, use of permethrin-treated clothing, sleeping in screened sleep spaces, and using an insecticide-treated bed net[23].
This report summarizes malaria cases reported to CDC with onset of symptoms in 2018, describes trends during previous years, and highlights information on risk factors and prevention. The intended audience includes public health authorities, health care providers, and persons traveling to areas with malaria transmission. Information on chemoprophylaxis, diagnosis, and treatment is provided for health care professionals and the public, and links to additional malaria information and resources are provided.