Chikungunya virus infection is transmitted by mosquitoes of the genus Aedes. The virus was first isolated in 1952 and is found in eastern Africa, India, and Southeast Asia. Symptoms of infection are high fever and disabling muscle and joint pain, often associated with a rash and mild bleeding. Persons infected usually recover spontaneously in several days to a week (1). Fever and arthralgia may occur for several months or even years (2). Patients are treated only for their symptoms because there is no specific treatment for the underlying infection (3). Before the recent outbreak on the island of Reunion, the disease was not considered life-threatening.
Reunion, a French territory in the southwestern Indian Ocean, has a population of [approximately equal to] 785,000 inhabitants. Medical facilities in Reunion are similar to those in mainland France and other industrialized countries. A major chikungunya outbreak occurred in Reunion in 2005-2006. At the end of this outbreak, seroprevalence was estimated to be 38.2% (95% confidence interval [CI] 35.9%-40.6%); 300,000 (95% CI 283,000-320,000) persons were infected (4,5). Aedes albopictus mosquitoes were the primary vector in this outbreak.
The outbreak began in eastern Africa (6). It reached Reunion in March 2005 but was relatively inactive, with only several thousand cases until November 2005, when its incidence unexpectedly increased during summer in the Southern Hemisphere, peaking at 47,000 cases/week during week 5 of 2006. The most recent cases were reported in August 2006. Comparisons of 2006 with previous years showed that mortality rates increased during February, March, and April 2006 (7,8). Since 2006, the virus has caused several epidemics in the Indian Ocean region (Madagascar, India, Sri Lanka, Thailand, Malaysia, and Singapore). Three new cases of chikungunya were reported in August 2009 on Reunion Island (9).
The first cases of virus transmission from mother to child at birth were identified in February 2006; a total of 38 such cases were reported (10,11). The virus was also found in specimens from 3 early second trimester miscarriages (12). When this outbreak began, little information was available about the risk for chikungunya virus infection in pregnant women. In addition to virus transmission at birth, potential complications include transplacental transmission before birth, congenital malformations, stillbirths, growth restriction, and preterm delivery. Chikungunya virus belongs to the same family of viruses (Togaviridae) as rubella virus, for which some of these complications have been described (13). The high fever that characterizes chikungunya infection could cause uterine contractions or fetal heart rate abnormalities, which might promote spontaneous or induced preterm delivery (cesarean for fetal salvage). The hemorrhagic syndrome described at the onset of infection might be manifested by vaginal bleeding during pregnancy or third-stage hemorrhaging, as reported for infection with dengue virus (14,15). The proportion of symptomatic and asymptomatic infections was also unknown.
The purpose of our study (the Chikungunya-Mere-Enfant cohort study) was to determine the consequences of chikungunya infection on pregnancy outcomes. These results will be useful to public health officials and physicians who provide care for pregnant women or newborns because chikungunya can...