Malaria Surveillance, United States 2019 – 2020

What to know

United States malaria surveillance data guides public health actions for preparedness, prevention, detection, and response at the patient, state, and federal levels. In 2019, 2,048 confirmed malaria cases were reported to the CDC National Malaria Surveillance System. Due to substantial reductions in foreign travel as a consequence of the COVID-19 pandemic, 602 malaria cases were reported to the CDC in 2020. Almost all cases reported in 2019 and 2020 were imported, or travel associated.

Overview

Malaria surveillance in the United States and its territories provides information on its occurrence (e.g., temporal, geographic, and demographic), informs recommendations for preventing malaria among travelers and guidelines for treating malaria patients, and facilitates rapid implementation of transmission control measures if locally acquired cases are identified.

Surveillance Methods

Malaria is nationally notifiable, and cases are reported directly from health departments, jurisdictions, and territories to the CDC program that implements the National Malaria Surveillance System (NMSS) as one of the diseases included in the National Notifiable Diseases Surveillance System (NNDSS).

As a notifiable condition, positive malaria laboratory test results are automatically reported from hospital, commercial, public health, and other laboratories to state and local health departments through the electronic laboratory reporting system. The electronic laboratory reports prompt investigations by state and local health departments, then case reports are submitted to CDC. Both systems rely on passive reporting from the jurisdictions, and the number of cases might differ, especially because of differences in date classifications. NNDSS report dates might be assigned according to the date of diagnosis, or the date reported to the health department, and NMSS assigns dates according to illness onset. This report summarizes data from the integration of all NMSS and NNDSS cases after deduplication and reconciliation. This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.1

Confirmed or suspected malaria in the United States is defined by the Council of State and Territorial Epidemiologists (CSTE) and CDC case definition. Malaria Surveillance and Case Investigation Best Practices, including resources on the malaria case definitions are available at the CDC website.

Data elements reported and analyzed include age, sex, pregnancy status, residence, illness onset date, laboratory results, travel history (countries, regions, and dates), chemoprophylaxis (medication used and adherence), history of malaria (date and species), blood transfusion or organ transplant history, hospitalization, clinical complications, treatment medications, illness outcome (survived versus died), and case classification. Data elements with missing values were excluded from analysis.

1 45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. §241(d); 5 U.S.C. §552a; 44 U.S.C. §3501 et seq.

Key findings

  • There were 2,048 confirmed malaria cases in 2019, compared to 1,823 confirmed cases reported in 2018. In 2020 there were 602 confirmed malaria cases reported, the lowest number since 1972.
  • There were more U.S. civilian cases in 2019 compared to 2018. Compared to 2019, in 2020 there were fewer cases across all residence categories.
  • For 2019 and 2020, the most common demographic characteristics among reported cases were males, those aged 18 – 64 years, non-Hispanic ethnicity, and Black/African American race.
  • In 2019 and 2020, Africa is the primary region of acquisition for travel-associated U.S. malaria cases, and cumulatively, more than half of all cases during these years were acquired from West Africa. In 2019 and 2020, ≤6% of cases were acquired from Asia, and 1% or fewer cases were acquired in South America, Central America and the Caribbean, the Middle East, and Oceania.
  • Among U.S. civilians, malaria cases reported visiting friends and relatives as the primary reason for travel in both years, followed by business travel.
  • Plasmodium falciparum (85.5% in 2019 and 77.2% in 2020) is the most common species diagnosed among the malaria cases with a species determination, followed by Plasmodium vivax (6.0% in 2019 and 12.1% in 2020) and Plasmodium ovale (4.9% in 2019 and 6.2% in 2020).
  • Thirteen states/jurisdictions in 2019 and twelve states/jurisdictions in 2020 were in the top quartile for having the most malaria cases. Eleven states/jurisdictions were in the top quartile for both years, and include New York City, Maryland, Texas, California, Pennsylvania, Virginia, New Jersey, Minnesota, North Carolina, Florida, and Ohio

What is CDC doing?

  • CDC supports U.S. states, territories, and jurisdiction health departments in the investigation, response and reporting of malaria cases.
  • CDC provides resources to health care providers in the United States including diagnosis and treatment guidelines and a 24/7/365 malaria hotline for clinicians and state and local health department staff.

Results

Number of malaria cases by species and year, 2014 – 2020

Number of malaria cases, by Plasmodium species and year — United States, 2014 – 2020
 Plasmodium
Species 		 2014 2015 2016 2017 2018 2019 2020
No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2
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) 1,533 (74.9) (85.5) 389 (64.6) (77.2)
P. vivax    230 (13.3) (15.1) 180 (11.8) (13.6) 251 (12.1) (13.6) 216 (10.0) (11.2) 173 (9.5) (10.8) 107 (5.2) (6.0) 61 (10.1) (12.1)
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) 87 (4.2) (4.9) 31 (5.2) (6.2)
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) (3.0) 53 (2.6) (3.0) 16 (2.7) (3.2)
P. knowlesi 0 (0.0) (0.0) 0 (0.0) (0.0) 0 (0.0) (0.0) 0 (0.0) (0.0) 1 (0.1) (0.1) 1 (0.1) (0.1) 0 (0.0) (0.0)
Mixed 15 (0.9) (1.0) 12 (0.8) (0.9) 23 (1.1) (1.2) 22 (1.0) (1.1) 17 (0.9) (1.1) 13 (0.6) (0.7) 7 (1.2) (1.4)
Undetermined 202 (11.7) 196 (12.9) 225 (10.8) 226 (10.5) 216 (11.9) 254 (12.4) 98 (16.3)


Total

 1,725 (100) (100) 1,524 (100) (100) 2,078 (100) (100) 2,161 (100) (100) 1,823 (100) (100) 2,048 (100) (100) 602 (100) (100)
1 Percentage among all infections
2 Percentage among infections with known species

For years 2014 – 2020, P. falciparum is the predominant species of malaria diagnosed in the United States, followed by P. vivax. The highest proportion of P. falciparum observed over this period occurred in 2019. 2020 had the lowest proportion of P. falciparum during this period. The proportion of the relapsing species (P. vivax and P. ovale) was higher in 2020 than in 2019.

Number of malaria cases by demographics, region of acquisition, and primary reason for travel, by patient resident status — United States, 2019

Demographic Table, 2019
U.S. Military U.S. Civilian Non-U.S. Not recorded Total
Demographics No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2
Total 23 1.1 — 1388 67.8 — 359 17.5 — 278 13.6 — 2,048 100 —
Male sex 22 95.7 — 910 65.6 — 209 58.2 58.4 176 63.3 — 1,317 64.3 64.3
Female sex 1 4.3 — 478 34.4 — 149 41.5 41.6 102 36.7 — 730 35.6 35.7
Unknown sex 0 0.0 — 0 0.0 — 1 0.3 — 0 0.0 — 1 0.0 —
Age less than 18 years 0 0.0 — 184 13.3 — 149 41.5 — 17 6.1 6.1 350 17.1 17.1
Age 18 – 64 years 23 100.0 — 1,081 77.9 — 186 51.8 — 233 83.8 84.1 1,523 74.4 74.4
Age 65 years and older 0 0.0 — 123 8.9 — 24 6.7 — 27 9.7 9.7 174 8.5 8.5
Age unknown 0 0.0 — 0 0.0 — 0 0.0 — 1 0.4 — 1 0.0 —
Not Hispanic or Latino 14 60.9 82.4 1,050 75.6 97.4 271 75.5 97.5 163 58.6 98.2 1,498 73.1 97.3
Hispanic or Latino 3 13.0 17.6 28 2.0 2.6 7 1.9 2.5 3 1.1 1.8 41 2.0 2.7
Unknown 6 26.1 — 310 22.3 — 81 22.6 — 112 40.3 — 509 24.9 —
Race Asian 0 0.0 0.0 28 2.0 2.3 30 8.4 9.7 6 2.2 3.0 64 3.1 3.6
Race Black or African American 10 43.5 47.6 1,017 73.3 82.0 255 71.0 82.3 169 60.8 83.7 1,451 70.8 81.8
Race White 10 43.5 47.6 141 10.2 11.4 18 5.0 5.8 20 7.2 9.9 189 9.2 10.7
Race Other 1 4.3 4.8 54 3.9 4.4 7 1.9 2.3 7 2.5 3.5 69 3.4 3.9
Race Unknown 2 8.7 — 148 10.7 — 49 13.6 — 76 27.3 — 275 13.4 —
Region of acquisition3 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2
Total 23 1.1 — 1,380 68.4 — 356 17.6 — 258 12.8 — 2,017 100 —
Africa 14 60.9 — 1,303 94.4 95.9 302 84.8 85.8 230 89.1 93.1 1,849 91.7 93.4
Asia 9 39.1 — 26 1.9 1.9 37 10.4 10.5 11 4.3 4.5 83 4.1 4.2
South America 0 0.0 — 13 0.9 1.0 5 1.4 1.4 2 0.8 0.8 20 1.0 1.0
Central America / Caribbean 0 0.0 —— 6 0.4 0.4 6 1.7 1.7 3 1.2 1.2 15 0.7 0.8
Oceania 0 0.0 — 8 0.6 0.6 1 0.3 0.3 1 0.4 0.4 10 0.5 0.5
Middle East 0 0.0 — 2 0.1 0.1 1 0.3 0.3 0 0.0 0.0 3 0.1 0.2
Unknown 0 0.0 — 22 1.6 — 4 1.1 — 11 4.3 — 37 1.8 —
Africa, West 7 30.4 — 935 67.8 68.9 156 43.8 44.3 151 58.5 61.1 1249 61.9 63.1
 
Primary reason for travel3 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2
Total 23 1.1 — 1,380 68.4 — 356 17.6 — 258 12.8 — 2,017 100 —
Visiting friends and relatives 0 0.0 — 828 60.0 79.0 49 13.8 17.6 45 17.4 75.0 922 45.7 65.4
Tourist 0 0.0 — 64 4.6 6.1 8 2.2 2.9 4 1.6 6.7 76 3.8 5.4
Missionary or dependent 0 0.0 — 58 4.2 5.5 0 0.0 0.0 1 0.4 1.7 59 2.9 4.2
Business 0 0.0 — 67 4.9 6.4 18 5.1 6.5 6 2.3 10.0 91 4.5 6.5
Student or teacher 0 0.0 — 17 1.2 1.6 17 4.8 6.1 4 1.6 6.7 38 1.9 2.7
Airline/ship crew 0 0.0 — 2 0.1 0.2 3 0.8 1.1 0 0.0 0.0 5 0.2 0.4
Peace Corps 0 0.0 — 5 0.4 0.5 0 0.0 0.0 0 0.0 0.0 5 0.2 0.4
Refugee or immigrant 0 0.0 — 0 0.0 0.0 174 48.9 62.4 0 0.0 0.0 174 8.6 12.3
Military deployment 23 100.0 — 0 0.0 0.0 2 0.6 0.7 0 0.0 0.0 25 1.2 1.8
Other 0 0.0 — 7 0.5 0.7 8 2.2 2.9 0 0.0 0.0 15 0.7 1.1
Unknown 0 0.0 — 332 24.1 — 77 21.6 — 198 76.7 — 607 30.1 —
1 Percentage calculated among all subjects
2 Percentage calculated among subjects with known responses
3 Among imported cases

In 2019, most people diagnosed with malaria in the United States were male, 18 – 64 years old, non-Hispanic or Latino ethnicity, and Black/African American race. Case patients predominantly traveled to Africa. More than half of all case patients traveled to or from West Africa. More than two thirds of U.S. civilians with malaria traveled to visit friends and relatives in 2019.

Number of malaria cases by demographics, region of acquisition, and primary reason for travel, by patient resident status — United States, 2020

Demographic Table, 2020
U.S. Military U.S. Civilian Non-U.S. Not recorded Total
Demographics No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2
Total 14 2.3 —   390 64.8 —   87 14.5 —   111 18.4 —   602 100 —
Male sex 12 85.7 — 247 63.3 — 56 64.4 — 73 65.8 — 388 64.5 —
Female sex 2 14.3 — 143 36.7 — 31 35.6 — 38 34.2 — 214 35.5 —
Age less than 18 years 0 0.0 — 29 7.4 — 30 34.5 — 12 10.8 10.8 71 11.8 —
Age 18 – 64 years 14 100.0 — 327 83.8 — 54 62.1 — 89 80.2 80.2 484 80.4 —
Age 65 years and older 0 0.0 — 34 8.7 — 3 3.4 — 10 9.0 9.0 47 7.8 —
Not Hispanic or Latino 7 50.0 100.0 302 77.4 97.7 60 69.0 95.2 90 81.0 100.0 459 76.2 97.9
Hispanic or Latino 0 0.0 0.0 7 1.8 2.3 3 3.4 4.8 0 0.0 0.0 10 1.7 2.1
Unknown 7 50.0 — 81 20.8 — 24 27.6 — 21 18.9 — 133 22.1 —
Race Asian 1 7.1 7.7 8 2.1 2.2 9 10.3 11.8 5 4.5 5.3 23 3.8 4.2
Race Black or African American 3 21.4 23.1 264 67.7 72.7 49 56.3 64.5 70 63.1 73.7 386 64.1 70.2
Race White 9 64.3 69.2 61 15.6 16.8 12 13.8 15.8 10 9.0 10.5 92 15.3 16.7
Race Other 1 0.0 0.0 27 7.7 8.3 11 12.6 7.9 10 9.0 10.5 49 8.1 8.9
Race Unknown 0 0.0 — 30 7.7 — 6 6.9 — 16 14.4 — 52 8.6 —
Region of acquisition3 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2
Total 14 2.4 —   383 66.3 —   86 14.9 —   95 16.4 —   578 100 —
Africa 5 35.7 — 344 89.8 94.0 69 80.2 82.1 72 75.8 92.3 490 84.8 90.4
Asia 9 64.3 — 11 2.9 3.0 11 12.8 13.1 4 4.2 5.1 35 6.1 6.5
South America 0 0.0 — 5 1.3 1.4 3 3.5 3.6 1 1.1 1.3 9 1.6 1.7
Central America / Caribbean 0 0.0 — 2 0.5 0.5 1 1.2 1.2 0 0.0 0.0 3 0.5 0.6
Oceania 0 0.0 — 4 1.0 1.1 0 0.0 0.0 0 0.0 0.0 4 0.7 0.7
Middle East 0 0.0 — 0 0.0 0.0 0 0.0 0.0 1 1.1 1.3 1 0.2 0.2
Unknown 0 0.0 — 17 4.4 — 2 2.3 — 17 17.9 — 36 6.2 —
Africa, West 3 21.4 — 208 54.3 56.8 26 30.2 31.0 43 45.3 55.1 280 48.4 51.7
Primary reason for travel3 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2 No. (%)1 (%)2
Total 14 2.4 —   383 66.3     86 14.9 —   95 16.4 —   578 100 —
Visiting friends and relatives 0 0.0 — 211 55.1 76.2 11 12.8 16.2 16 16.8 80.0 238 41.2 62.8
Tourist 0 0.0 — 15 3.9 5.4 1 1.2 1.5 1 1.1 5.0 17 2.9 4.5
Missionary or dependent 0 0.0 — 19 5.0 6.9 1 1.2 1.5 0 0.0 0.0 20 3.5 5.3
Business 0 0.0 — 24 6.3 8.7 0 0.0 0.0 1 1.1 5.0 25 4.3 6.6
Student or teacher 0 0.0 — 3 0.8 1.1 4 4.7 5.9 1 1.1 5.0 8 1.4 2.1
Airline/ship crew 0 0.0 — 1 0.3 0.4 1 1.2 1.5 0 0.0 0.0 2 0.3 0.5
Peace Corps 0 0.0 — 3 0.8 1.1 0 0.0 0.0 0 0.0 0.0 3 0.5 0.8
Refugee or immigrant 0 0.0 — 0 0.0 0.0 49 57.0 72.1 0 0.0 0.0 49 8.5 12.9
Military deployment 14 100.0 — 0 0.0 0.0 0 0.0 0.0 0 0.0 0.0 14 2.4 3.7
Other 0 0.0 — 1 0.3 0.4 1 1.2 1.5 1 1.1 5.0 3 0.5 0.8
Unknown 0 0.0 — 106 27.7 — 18 20.9 — 75 78.9 — 199 34.4 —
1 Percentage calculated among all subjects
2 Percentage calculated among subjects with known responses
3 Among imported cases

In 2020, most people diagnosed with malaria in the United States were male, 18 – 64 years old, non-Hispanic or Latino ethnicity, and Black/African American race. Case patients predominantly traveled to Africa. More than half of all case patients traveled to or from West Africa.  More than half of U.S. civilians with malaria traveled to visit friends and relatives in 2020.

The stacked bar graph shows the number of cases by illness onset month. The species determination for each case is colored (P. falciparum in blue, P. vivax and P. ovale in orange, and other or unknown species in green). In 2019, the lowest number of cases had illness onset in February through April; the highest number of cases were in July through September. In 2020, the lowest number of malaria cases were in April through June 2020. The highest number of malaria cases had illness onset in January 2020. In both years, Plasmodium falciparum made up the highest proportion of cases. Compared to 2019, in 2020 the proportion of P. vivax and P. ovale species was higher.

Supplementary data files

Downloadable data files‎

Tables with case counts by species, country of acquisition, and diagnostic confirmation method (e.g., blood smear microscopy only, or polymerase chain reaction confirmed [with or without blood smear microscopy]) are available for download for years 2019 and 2020.

References

Print
Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)