Chikungunya Virus Infection during Pregnancy, Réunion, France, 2006

Abstract

Mother-to-child transmission of chikungunya virus was reported during the 2005-2006 outbreak on Réunion Island, France.To determine the effects of this virus on pregnancy outcomes, we conducted a study of pregnant women in Réunion in 2006.The study population was composed of 1,400 pregnant women (628 uninfected, 658 infected during pregnancy, 27 infected before pregnancy, and 87 infected on unknown dates).We compared pregnancy outcomes for 655 (628 + 27) women not infected during pregnancy with 658 who were infected during pregnancy.Infection occurred during the fi rst trimester for 15% of the infected women, the second for 59%, and the third for 26%.Only hospital admission during pregnancy differed between infected and uninfected women (40% vs. 29%).Other outcomes (cesarean deliveries, obstetric hemorrhaging, preterm births, stillbirths after 22 weeks, birthweight, congenital malformations, and newborn admissions) were similar.This virus had no observable effect on pregnancy outcomes. C hikungunya virus infection is transmitted by mosqui-toes of the genus Aedes.The virus was fi rst 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 specifi c treatment for the underlying infection (3).Before the recent outbreak on the island of Réunion, the disease was not considered life-threatening.Réunion, a French territory in the southwestern Indian Ocean, has a population of ≈785,000 inhabitants.Medical facilities in Réunion are similar to those in mainland France and other industrialized countries.A major chikungunya outbreak occurred in Réunion in 2005-2006.At the end of this outbreak, seroprevalence was estimated to be 38.2%(95% confi dence 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 Réunion 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 Réunion Island (9).The fi rst cases of virus transmission from mother to child at birth were identifi ed in February 2006; a total of 38 such cases were reported (10,11).The virus was also found Chikungunya Virus Infection during Pregnancy, Réunion, France, 2006