TravelByte #40: CDC Malaria Surveillance Update

Editor’s Note: This month Julie Richards shares a synopsis and commentary on some of the key data from the recent CDC malaria surveillance report (March 2021). Annually, CDC publishes a report in the MMWR that shares recent and comprehensive malaria data available for U.S. travelers. The report is an excellent review and update on malaria prevention, diagnosis and treatment in the U.S. and should be required reading for any travel health nurse who counsels patients about malaria pre- or post- travel.

Most readers are surprised to see that the report captures data that is always two or more years previous. The explanation: it requires more than a year to just collect data from the previous year, data is then “cleaned,” verified, analyzed and subsequently reviewed and published. Due to Covid, this latest data report is for 2017, but still provides travel health nurses with important trends and emerging issues.

As Julie’s summary demonstrates, malaria cases among U.S. citizens continue to increase and West African travel continues to generate the highest number of cases. This is consistent with a trend since the mid-1970’s. Civilian travel and nonadherence to chemoprophylaxis continue to impact malaria case numbers in this country.

Next Month: ATHNA will publish a special TravelByte on the 2018 approved malaria drug, tafenoquine, so all travel health nurses are aware of contraindications, precautions, and practical issues of use. A review of G6PD deficiency and testing, critical to the use of tafenoquine, will be included.

Mace KE, Lucchi NW, Tan KR. Malaria Surveillance — United States, 2017. MMWR Surveill Summ 2021;70(No. SS-2):1–35. DOI: icon

  • In 2017 there were 2,161 cases of malarial in the US – the highest in 45 years. There were 7 deaths.
  • Despite recent gains, malaria is still endemic in 90 countries and territories; thus 1/2 of the world population is at risk for infection
  • 78.8% of the cases where species ID was possible were Plasmodium falciparum, next was P. vivax (11.2% of infections)
  • 86.7% of the cases originated in Africa, with a higher proportion originating in West Africa (57.6%) than in 2016 (51.6%).
  • All states except Wyoming reported cases with the four highest: New York City, Maryland, Texas and California.
  • Of the U.S. civilian patients who reported reason for travel, 73.1% were visiting friends and relatives, missionary travel was reported for 91 (8.8%), business travel was reported for 88 (8.5%), and tourism was reported for 60 (5.8%) patients.
  • The proportion of U.S. residents with malaria who reported taking any chemoprophylaxis in 2017 (28.4%) was similar to that in 2016 (26.4%), and adherence was poor among those who took chemoprophylaxis. Among the 996 U.S. residents with malaria for whom information on chemoprophylaxis use and travel region were known, 93.3% did not adhere to or did not take a CDC-recommended chemoprophylaxis regimen.
  • Among 1,203 patients with P. falciparum infections, 1,160 (96.4%) had symptom onset before or within 29 days of arrival in the United States. In contrast, 58 (40.6%) of 143 P. vivax patients and 42 (52.5%) of 80 P. ovale patients had illness onset ≥30 days after arrival in the United States, consistent with the potential for these species to relapse because of the persistence of liver hypnozoites or to have an extended incubation period before symptom onset (35).
  • 33.3% of samples exhibited resistance to chloroquine, 2.7% to mefloquine, 2/75 to atovaquone, and thankfully no cases were resistant to artemisinin. 
  • Interesting tidbit of history – while the US eradicated malaria in 1951, from 1957-2003, the US has had 63 outbreaks of malaria, which is why mosquito surveillance is so important. Many parts of the US have Anopheles vectors. The last outbreak was in Palm Beach, FL.
  • Definitions are important. Severe malaria includes altered consciousness (cerebral malaria), seizures, severe anemia (hemoglobin <7g/dL), acute kidney injury, liver failure, respiratory distress coma, permanent disability, and death. Malaria must be in the differential for all persons reporting fever who traveled to areas where malaria is endemic. Travel nurses must be advocates for these patients ensuring that smears (to establish parasitemia levels that impact treatment), PCR (identifies species), and RDTs are done appropriately in a timely fashion. If you notice a HgB <7 – that would be a significant clue in someone who has not been evaluated for malaria yet. 

I would encourage all travel nurses to read the original document for more interesting details and content that hasn’t been included previously in other surveillance reports (e.g. agencies involved in surveillance, mosquito monitoring, resistance testing).


October 2021