Date Published: March 18, 2008
Publisher: Public Library of Science
Author(s): Patrick Gérardin, Georges Barau, Alain Michault, Marc Bintner, Hanitra Randrianaivo, Ghassan Choker, Yann Lenglet, Yasmina Touret, Anne Bouveret, Philippe Grivard, Karin Le Roux, Séverine Blanc, Isabelle Schuffenecker, Thérèse Couderc, Fernando Arenzana-Seisdedos, Marc Lecuit, Pierre-Yves Robillard, Jean-Paul Chretien
Abstract: BackgroundAn outbreak of chikungunya virus affected over one-third of the population of La Réunion Island between March 2005 and December 2006. In June 2005, we identified the first case of mother-to-child chikungunya virus transmission at the Groupe Hospitalier Sud-Réunion level-3 maternity department. The goal of this prospective study was to characterize the epidemiological, clinical, biological, and radiological features and outcomes of all the cases of vertically transmitted chikungunya infections recorded at our institution during this outbreak.Methods and FindingsOver 22 mo, 7,504 women delivered 7,629 viable neonates; 678 (9.0%) of these parturient women were infected (positive RT-PCR or IgM serology) during antepartum, and 61 (0.8%) in pre- or intrapartum. With the exception of three early fetal deaths, vertical transmission was exclusively observed in near-term deliveries (median duration of gestation: 38 wk, range 35–40 wk) in the context of intrapartum viremia (19 cases of vertical transmission out of 39 women with intrapartum viremia, prevalence rate 0.25%, vertical transmission rate 48.7%). Cesarean section had no protective effect on transmission. All infected neonates were asymptomatic at birth, and median onset of neonatal disease was 4 d (range 3–7 d). Pain, prostration, and fever were present in 100% of cases and thrombocytopenia in 89%. Severe illness was observed in ten cases (52.6%) and mainly consisted of encephalopathy (n = 9; 90%). These nine children had pathologic MRI findings (brain swelling, n = 9; cerebral hemorrhages, n = 2), and four evolved towards persistent disabilities.ConclusionsMother-to-child chikungunya virus transmission is frequent in the context of intrapartum maternal viremia, and often leads to severe neonatal infection. Chikungunya represents a substantial risk for neonates born to viremic parturients that should be taken into account by clinicians and public health authorities in the event of a chikungunya outbreak.
Partial Text: The chikungunya virus (CHIKV) is an enveloped, positive-strand RNA alphavirus belonging to the Togaviridae family and transmitted by Aedes mosquito bites . It causes a dengue-like illness, characterized by fever, rash, painful myalgia, and arthralgia, and sometimes arthritis . It was first isolated by R.W. Ross in 1952 in the Newala district of Tanzania . Its current geographic distribution covers sub-Saharan Africa, Southeast Asia, India, and the Western Pacific where numerous outbreaks have been reported [4–8]. In these areas, upsurges of re-emergence occur at intervals of 7 to 20 years .
During this 22-mo long survey (March 2005 to December 2006), 7,504 consecutive women delivered 7,629 viable neonates at the level-3 GHSR maternity department whilst about 2,000 births occurred in the level-1 maternity department. The monthly evolution of the cumulative incidence of maternal chikungunya infections during pregnancy and that of neonatal cases observed in the GHSR level-3 maternity are presented in Figure 1. The first reported antepartum case occurred in May 2005 (third month after the beginning of the outbreak, m3) and the last in June 2006 (m16). During the first 9 mo of the outbreak (cold season in the Southern hemisphere), the attack rate among pregnant women was below 1% and the prevalence rate among parturient women was below 5%, owing to a sporadic transmission (fewer than ten cases per week). At m10, the hot and rainy season (austral summer) started, and the attack rates increased sharply during m10–m12 in the general population (45,000 new cases during the first week of February 2006). For pregnant women, the incidence peaked in January 2006 (m11) with an attack rate of 8.3% (95% confidence interval [CI] 7.4%–9.3%). Among parturient women, the peak of prevalence was delayed to m15 with a 27.5% reported rate. Between m13 and m16 the attack rates decreased sharply to 0.4% (95% CI 0.15%–0.6%) and then prevalence rates felt dramatically to reach only 0.4% in December 2006 (m22), marking the end of our survey.
Here we report the epidemiological, clinical, biological, and radiological features and outcomes of maternal-fetal transmission of CHIKV infection in an outbreak that occurred on the island of La Réunion, France. We find that mother-to-child CHIKV transmission is almost exclusively observed in the context of intrapartum maternal viremia, and often leads to severe neonatal infection. CHIKV thus represents a significant risk for neonates born from viremic parturients that must be taken into account by clinicians and public health authorities in the event of a chikungunya outbreak.