CDC Updates from American Society of Tropical Medicine and Hygiene — 2009 Annual Meeting, Washington, DC

Abstract & Commentary

By Lin H. Chen, MD

Dr. Chen is Assistant Clinical Professor, Harvard Medical School Director, Travel Medicine Center, Mt. Auburn Hospital, Cambridge, MA.

Dr. Chen reports no financial relationships relevant to this field of study.

Synopsis: At the 58th Annual Meeting of the American Society of Tropical Medicine and Hygiene held November 18-22, 2009, in Washington, DC, Dr. Paul Arguin, Chief of Domestic Malaria Unit, presented the CDC Malaria Update for 2009.

From 1985 to 2008, the malaria surveillance program in the United States recorded an average of 1400 malaria cases and 5 deaths per year. In 2008, 1298 cases were reported, including one congenital case. Among the reported cases, at least 537 patients (41%) were hospitalized, and at least 117 cases (9%) were severe, with 82% attributed to Plasmodium falciparum and 8% attributed to P. vivax. There were 2 deaths, one each due to P. falciparum and P. vivax. The population sectors of reported malaria cases were: 39% civilian, 14% foreign civilian, 1% military, 46% unknown. Among U.S. residents for whom the reason for travel was noted, 62.7% traveled to visit friends and relatives, 7.6% traveled for volunteer or missionary work, 6.8% traveled for business, and 6.0% traveled for tourism. The major region of acquisition was Africa (43% of all cases) or unknown (39%). Principal countries in which U.S. residents acquired malaria were Nigeria (26.3%), Ghana (14.6%), India (10.4%), and Ivory Coast (5.4%). The species distribution is similar to the past, with P. falciparum leading (40.6%), followed by P. vivax (14.6%), P. malariae (1.5%), P. ovale (1.4%), mixed (0.6%), and with the "undetermined species" category high at 41.2%.

Malaria diagnosis continues to rely on microscopic examination of Giemsa-stained smears. Alternatives to this gold standard include Wright stain and rapid diagnostic tests (RDTs) for acute management, although RDTs cannot yet replace microscopy. The Food and Drug Administration recently approved a positive control solution, which should strengthen the interpretation of RDTs.

Treatment for uncomplicated malaria has broadened to include the newly FDA-approved artemether-lumefantrine, with a twice-daily dosing regimen for 3 days. Artemether-lumefantrine may be associated with slight Q-T prolongation and should not be used during pregnancy. It is indicated only for uncomplicated malaria and might be considered for travelers who may need a reliable supply for potential malaria treatment.

For severe malaria, artesunate continues to be available under an IND (Investigational New Drug) protocol through the CDC and shipped from the major quarantine stations. Since it became available in 2007, 81 authorizations have occurred, and 66 patients have been treated in 26 states. The average time from request to initial infusion is 7.2 hours. The average age among those treated was 38 years, 89% were P. falciparum, 56% were mixed infections, 5% were P. vivax, and 2% were P. ovale.

The presentation also revisited the issue of malaria and the blood supply. There is no approved or adequate laboratory test for screening the blood supply for malaria. In the United States, transfusion-associated malaria occurs at a low rate of 0.5 case/year. Potential blood donors who have traveled to malaria risk areas are deferred for a year, which is estimated at 150,000 potential donors per year. About 35,000 potential donors per year in the United States are deferred due to travel to the state of Quintana Roo, Mexico, where there were fewer than 10 locally transmitted cases in 2009. On November 16, 2009, the Blood Products Advisory Committee to the FDA voted to allow travelers to Quintana Roo to donate blood.

Finally, the interactive malaria map has been updated and is available at http://cdc-malaria.ncsa.uiuc.edu. Users can search for the presence of malaria, malaria parasite types, drug resistance, and recommended chemoprophylaxis choices for locations throughout the world. Newly added features include descriptions of risk according to altitude.

Dr. Gary Brunette, Chief of Travelers' Health Branch in the Division of Global Migration and Quarantine, presented vaccine changes impacting travelers during the CDC Travelers Vaccines Update. Highlighted changes that have been published recently include: expansion of influenza vaccine recommendations to include children aged 6 months to 18 years; identification of priority groups for novel influenza A (H1N1) vaccines and schedules; revaccination of high-risk groups for meningococcal disease at 5 years following previous meningococcal vaccine if vaccinated at age 7 years or older and at 3 years if previously vaccinated at ages 2-6 years; addition of contacts of international adoptees to the priority group for hepatitis A vaccine recommendations; specification of the interval between doses 4 and 5 of polio vaccine to be 6 months and to be given at age 4 years or older.

In addition, provisional recommendations have been made for rabies post-exposure prophylaxis, reducing the vaccine series from 5 doses to 4, in addition to human rabies immune globulin. Extensive literature review found no significant advantage to administering 5 doses over 4 doses.

The newly approved Japanese encephalitis (JE) vaccine received FDA licensure in March 2009, leading to refinement of JE vaccine recommendations. The new JE vaccine (Ixiaro®) is recommended for travelers staying 1 month or longer in JE endemic areas during the JE virus transmission season, and also should be considered for travelers to endemic areas for stays of 1 month or less with travel outside of urban areas and with increased JE virus exposure (i.e., ongoing JE outbreak at destination or an itinerary with uncertain destination, activities, or duration).

The provisional recommendations drafted by the ACIP YF Vaccine Working Group were pending at the time of the ASTMH meeting and recently posted. Anticipated changes include refinements to wording, which specify that the vaccine should be used only in persons at risk of exposure to yellow fever virus or who will be required to prove receipt of yellow fever vaccine for entry into certain countries. Furthermore, wording will be stronger for providers to carefully observe contraindications and consider precautions prior to administration of yellow fever vaccine. Added to the YF vaccine contraindications are thymus disorders, expanded lists of immunodeficiencies, and immunosuppressive and immunomodulatory therapies. Additional YF vaccine precautions include age 60 years or older, HIV infection with moderate immune suppression, pregnancy and breastfeeding.

Finally, Dr. Brunette described the CDC Travelers' Health media campaign. The spring 2009 H1N1 outbreak led to the recognition of the difficulty reaching travelers before transit, that messages were too text-dense and quickly outdated, and that channels were lacking to engage partners. Goals for the campaign include use of broad-based messages to inform and educate U.S. travelers, with pre- and during-travel messages and audience-specific communication initiatives (such as student travel), and specific seasonal or special-occasion promotions (i.e., holiday travel, spring break).

Acknowledgment: The associate editor thanks Drs. Paul Arguin and Gary Brunette for sharing their slides and for their review.

References

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