|Credit MMWR Mar. 8th|
The CDC has published a lengthy and detailed Early Release MMWR report on the surveillance for and detection of an increased incidence of Microcephaly reported in Northeastern Brazil concurrent with their Zika virus Epidemic.
As with the other studies we've seen, this one is subject to a number of limitations, is based on data collection and validation that is still in progress, and and does not prove causality.
Despite those constraints, this is another study that - like nearly everything else we've seen so far - seems to point in the general direction of causality. I've only excerpted a small portion of the study. Follow the link to read:
Wanderson Kleber de Oliveira, MSc1; Juan Cortez-Escalante, MD2; Wanessa Tenório Gonçalves Holanda De Oliveira, MSc1; Greice Madeleine Ikeda do Carmo, MSc1; Cláudio Maierovitch Pessanha Henriques, MD1; Giovanini Evelim Coelho, PhD1; Giovanny Vinícius Araújo de França, PhD1
Widespread transmission of Zika virus by Aedes mosquitoes has been recognized in Brazil since late 2014, and in October 2015, an increase in the number of reported cases of microcephaly was reported to the Brazil Ministry of Health.*
By January 2016, a total of 3,530 suspected microcephaly cases had been reported, many of which occurred in infants born to women who lived in or had visited areas where Zika virus transmission was occurring. Microcephaly surveillance was enhanced in late 2015 by implementing a more sensitive case definition. Based on the peak number of reported cases of microcephaly, and assuming an average estimated pregnancy duration of 38 weeks in Brazil (1), the first trimester of pregnancy coincided with reports of cases of febrile rash illness compatible with Zika virus disease in pregnant women in Bahia, Paraíba, and Pernambuco states, supporting an association between Zika virus infection during early pregnancy and the occurrence of microcephaly.
Pregnant women in areas where Zika virus transmission is occurring should take steps to avoid mosquito bites. Additional studies are needed to further elucidate the relationship between Zika virus infection in pregnancy and microcephaly.
The sudden and marked increase in birth prevalence of microcephaly in multiple states in Brazil temporally associated with documented widespread transmission of Zika virus provides additional evidence for the role of Zika virus infection during the first trimester of pregnancy; Zika virus has been demonstrated to cross the placenta, has been associated with congenital infection, and has been recovered in neural tissue (9,10).
There is an urgent need for additional research to confirm the link between Zika virus infection and microcephaly through prospective and retrospective analytic studies, as well as to determine the critical Zika virus exposure period during pregnancy with respect to possible fetal infection and microcephaly. Pregnant women should protect themselves from mosquito bites by wearing long sleeves and long pants, applying insect repellent, and when spending time indoors, ensure that rooms are protected by screens or mosquito nets.
SummaryWhat is already known about this topic?An outbreak of Zika virus disease, caused by a flavivirus transmitted by Aedes mosquitoes, occurred in Brazil in early 2015. An increase in the prevalence of infants born with microcephaly has been reported in Brazil since October 2015, in association with clusters of febrile rash illness in pregnant women.
What is added by this report?The birth prevalence of microcephaly in Brazil increased sharply during 2015–2016. The largest increase occurred in the Northeast region, where Zika virus transmission was first reported in Brazil. This analysis of 574 cases of microcephaly, detected through a newly established ad hoc microcephaly surveillance system, identified temporal and geospatial evidence linking the occurrence of febrile rash illness consistent with Zika virus disease during the first trimester of pregnancy with the increased birth prevalence of microcephaly. The prevalence of microcephaly in 15 states with laboratory-confirmed Zika virus transmission (2.8 cases per 10,000 live births) significantly exceeded that in four states without confirmed Zika virus transmission (0.6 per 10,000).
What are the implications for public health practice?The suggested link between maternal exposure to Zika virus infection during the first trimester of pregnancy and the increased birth prevalence of microcephaly provide additional evidence for congenital infection with Zika virus. Ongoing surveillance is needed to identify additional cases and to fully elucidate the clinical spectrum of illness. Pregnant women should protect themselves from mosquito bites by wearing protective clothing, applying insect repellents, and when indoors, ensuring that rooms are protected with screens or mosquito nets.