1. Universidad Peruana Cayetano Heredia, Lima, Peru;
2. U.S. Naval Medical Research Unit No. 6, Callao, Peru;
3. Armed Forces Health Surveillance Center, Silver Spring, Maryland;
4. Tulane School of Public Health and Tropical Medicine, New Orleans, Louisiana;
5. Viral and Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, Maryland