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Previous Volume 360:2536-2543 June 11, 2009 Number 24 Next

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ABSTRACT

Background In 2007, physicians on Yap Island reported an outbreak of illness characterized by rash, conjunctivitis, and arthralgia. Although serum from some patients had IgM antibody against dengue virus, the illness seemed clinically distinct from previously detected dengue. Subsequent testing with the use of consensus primers detected Zika virus RNA in the serum of the patients but no dengue virus or other arboviral RNA. No previous outbreaks and only 14 cases of Zika virus disease have been previously documented.

Methods We obtained serum samples from patients and interviewed patients for information on clinical signs and symptoms. Zika virus disease was confirmed by a finding of Zika virus RNA or a specific neutralizing antibody response to Zika virus in the serum. Patients with IgM antibody against Zika virus who had a potentially cross-reactive neutralizing-antibody response were classified as having probable Zika virus disease. We conducted a household survey to estimate the proportion of Yap residents with IgM antibody against Zika virus and to identify possible mosquito vectors of Zika virus.

Results We identified 49 confirmed and 59 probable cases of Zika virus disease. The patients resided in 9 of the 10 municipalities on Yap. Rash, fever, arthralgia, and conjunctivitis were common symptoms. No hospitalizations, hemorrhagic manifestations, or deaths due to Zika virus were reported. We estimated that 73% (95% confidence interval, 68 to 77) of Yap residents 3 years of age or older had been recently infected with Zika virus. Aedes hensilli was the predominant mosquito species identified.

Conclusions This outbreak of Zika virus illness in Micronesia represents transmission of Zika virus outside Africa and Asia. Although most patients had mild illness, clinicians and public health officials should be aware of the risk of further expansion of Zika virus transmission.

Source Information

From the Division of Vector-Borne Infectious Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, Centers for Disease Control and Prevention (CDC), Fort Collins, CO (M.R.D., A.M.P., R.S.L., A.G., A.J.L., J.L., O.K., A.P., B.J.B., M.F., E.B.H.); the Epidemic Intelligence Service Field Assignments Branch, CDC, Atlanta (T.-H.C., S.H., C.D.); the Wa'ab Community Health Center (W.T.H., M.B.) and the Yap State Department of Health Service (M.M.) — both in Yap, Federated States of Micronesia; the Office for the South Pacific, World Health Organization, Suva, Fiji (J.L.K.); the Department of Health, Education, and Social Affairs, Pohnpei, Federated States of Micronesia (M.P.); and the Pasteur Institute, Noumea, New Caledonia (L.G.).

Address reprint requests to Dr. Fischer at the Arboviral Diseases Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, 3150 Rampart Rd., Fort Collins, CO 80521, or at mfischer{at}cdc.gov.

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