A total of 1727 cases of malaria were reported to the CDC in 2013, a 2% increase over the number reported in 2012. These included two cases of congenital malaria. The majority (61%) were caused by Plasmodium falciparum, with 14% caused by P. vivax, 4% by P. ovale, and 3% by P. malariae, with 40 (2%) patients being infected with two species. The infecting species were unknown or unreported in 17%.
P. falciparum accounted for 85% of infections acquired in Africa, 73% in Central America and the Caribbean, 24% in South America, 14% in Oceania, and 9% in Asia. Infections attributed to P. vivax accounted for 86% acquired in Oceania, 80% in Asia, 67% in South America, 22% in Central America and the Caribbean, and 5% in Africa.
West African countries were the source of two-thirds of infections acquired within Africa. While the number of cases acquired in South Asia decreased significantly from 183 in 2012 to 147 in 2013, India, nonetheless, was in the top five countries of acquisition. There was also a 40% decrease in cases acquired in Central America and the Caribbean in 2013 compared with 2012; this decrease was entirely the result of a 37% decrease in cases from Haiti (35 in 2012 and 22 in 2013). The number of cases acquired in South America, the majority of which were acquired in Guyana and Peru, was little changed from previous years (35 in 2011, 41 in 2012, and 53 in 2013).
Among those for whom the reason for travel was known, 70% had been visiting friends and/or relatives. Only 4% of those for whom the information was available reported adherence to an appropriate CDC-recommended chemoprophylaxis regimen. None of the 36 pregnant women with malaria had adhered to chemoprophylaxis.
Only 12% had their symptom onset before arrival in the United States. In the other 88% with onset in the United States, malaria symptoms first occurred in the first month after arrival in 81% with P. falciparum infection and 45% of those infected with P. vivax. Of the 643 patients with P. falciparum infection, 551 (86%) received appropriate therapy. Of note is that among the 92 patients with this infection who were inappropriately treated were four who were pregnant. Of the 145 P. vivax-infected subjects who received appropriate treatment for the acute infection, only 43% fewer were also given primaquine for relapse prevention — something that the CDC recommends for all cases of mosquito-acquired P. vivax infections.
The infection was classified as severe in 279 (16%) patients, and 10 died; the latter was the largest number of reported deaths in patients with malaria in the United States since 2001. Of the 36 cases among pregnant women, eight (22%) cases were severe, all of whom survived. Among the 29 cases for whom the infecting species was known, 22 (76%) were diagnosed with P. falciparum infection, including all eight who presented with severe malaria.
A total of 137 blood samples submitted to CDC were tested for molecular markers associated with antimalarial drug resistance. Of the 100 P. falciparum-positive samples, 95 were tested for pyrimethamine resistance and 88 (93%) had genetic polymorphisms associated with pyrimethamine drug resistance, 74 (76%) with sulfadoxine resistance, 53 (53%) with chloroquine resistance, and one (1%) with atovaquone resistance. None had polymorphisms associated with either mefloquine or artemisinin resistance.
COMMENTARY
There has been an overall trend of an increasing number of malaria cases in the United States reported to CDC since 1973, with the number reported in 2013 being the third highest annual total since that year (see Figure 1). Despite progress in reducing the global burden of malaria, the disease remains endemic in many regions, and the use of appropriate prevention measures by travelers continues to be inadequate. Lack of adherence to appropriate recommended chemoprophylaxis remains the most important risk factor for the acquisition of malaria subsequently diagnosed in the United States.
Figure 1. Number of Malaria Cases Among U.S. Military Personnel and U.S. and Foreign Civilians — United States, 1973–2013*
*R2 = 0.6857 is the average rate in rise of cases over time.
SOURCE: Centers for Disease Control and Prevention
Three of the fatal cases illustrate the importance of early diagnosis and treatment. Of these, one ignored symptoms, with a resultant delay in seeking medical care. Another was initially treated with an orally administered regimen despite having a high level of parasitemia, and one was discharged from the emergency department with antibacterial therapy despite having returned from a malaria-endemic country.
Although CDC continues to recommend IV quinidine for parenteral therapy of malaria, evidence increasingly points to the superiority of IV artesunate. The latter, however, is not FDA-approved and must be obtained through CDC. Artesunate is stocked at nine sites around the United States and can be rapidly shipped at no cost to clinicians. Certain guidelines and eligibility requirements must be met to enroll a patient in the treatment protocol. Physicians who administer the drug to patients must notify CDC of any adverse event after administration and comply with the IND protocol. To enroll a patient with severe malaria in this treatment protocol, healthcare providers should call the CDC Malaria Hotline at (770) 488-7788 or toll-free at (855) 856-4713, Monday–Friday, 9 a.m.–5 p.m., Eastern time. At other times, callers should telephone (770) 488-7100 and ask to speak with a CDC Malaria Branch clinician. Travelers and healthcare providers are encouraged to use CDC resources on malaria prevention and treatment (see Table 1), and contact the CDC Malaria Branch for assistance with diagnostic or case management needs.
Table 1. Sources for Malaria Prophylaxis, Diagnosis, and Treatment Recommendations
|
Type of |
Source |
Availability |
Telephone number, internet address, or electronic mail address |
|
*These numbers are meant for use by healthcare professionals only. SOURCE: Centers for Disease Control and Prevention |
|||
|
Prophylaxis |
CDC’s 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 |
Order from Oxford
Order Fulfillment |
800-451-7556 or http://www.oup.com/us/ |
|
|
CDC’s Malaria Branch Internet site with Malaria Information and |
24 hours/day |
http://www.cdc.gov/malaria/travelers/country_table/a.html |
|
|
CDC Malaria Map Application |
24 hours/day |
http://www.cdc.gov/malaria/map |
|
|
Diagnosis |
CDC’s Division of Parasitic Diseases and Malaria diagnostic internet site (DPDx) |
24 hours/day |
http://www.dpd.cdc.gov/dpdx |
|
CDC’s Division of Parasitic Diseases and Malaria diagnostic CD-ROM (DPDx) |
Order by electronic mail from CDC Division of Parasitic Diseases and Malaria |
||
|
Treatment |
CDC Malaria Branch |
9:00 am–5:00 pm Eastern time, Monday–Friday |
770-488-7788 or toll-free 855-856-4713* |
|
CDC Malaria Branch |
5:00 pm–9:00 am Eastern time on weekdays and all day weekends and holidays |
770-488-7100* (This number is for the CDC’s Emergency Operations Center. Ask staff member to page the person on call for the Malaria Branch.) |
|
The number of reported cases of malaria in the United States in 2013 increased slightly over the previous year, while the 10 reported deaths were the most since 2001.
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