SHORT REPORT: O'NYONG-NYONG FEVER IN WEST AFRICA

During the fall of 2003, an outbreak of a febrile illness with rash, initially reported to be measles, occurred in the Nicla Border Camp in western Cote d’Ivoire, where approximately 8,000 Liberian refugees were awaiting resettlement to the United States. To define the risk of disease transmission to people in other populations during the resettlement, we determined the cause of the outbreak. The International Organization for Migration (an international health organization contracted by the Bureau of Population, Refugees, and Migration, U.S. Department of State, to perform preimmigration medical screening) administered a survey to 31 ill refugees that were easily accessible to collect epidemiologic and clinical information about the outbreak. In addition, acuteand convalescent-phase serum specimens were collected from these refugees and sent to the Centers for Disease Control and Prevention (CDC) for laboratory analysis. Among ill refugees surveyed, 28 (90%) reported fever, 26 (84%) a maculopapular rash, 27 (87%) pruritis, 22 (71%) myalgias, 18 (58%) arthralgias, and 10 (32%) reported household contacts with the same illness. Results of laboratory tests at CDC for eight (26%) of those surveyed were consistent with O’nyong-nyong virus infection (ONNV) by either serologic tests or ONNV-specific real-time polymerase chain reaction assay (TaqMan). Serologic testing for other causes of febrile rash illnesses, including measles, was negative. Because of the political situation, we were unable to investigate this outbreak more fully; thus, the total number of affected refugees or individuals in the surrounding community is unknown. Human infections with ONNV have only been documented in eastern Africa. However, infections caused by both IgboOra virus (presumed to be a strain of ONNV, based on 98.5% genomic identity with ONNV) 1 and Chikungunya virus (another related alphavirus) have caused similar human disease in western Africa, including Nigeria, Senegal, and Guinea Bissau. 2,3 In the current outbreak, an initial diagnosis of measles delayed the implementation of measures to stop the outbreak, such as spraying mosquito adulticide and providing bed nets. Moreover, because mosquitoes of the same genus as the known African vectors occur in North America, refugee movement was delayed until control measures were implemented and the outbreak was under control to prevent importation of disease. When outbreaks of febrile rash illnesses occur among large populations of people living in crowded conditions, laboratory confirmation is essential, and arbovirus etiologies should be considered.