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Two New Zika Virus Studies You Need to Know

For example, the results of an upcoming Emerging Infectious Diseases (EID) study suggest that surveillance for adverse pregnancy outcomes after a Zika epidemic should be longer than initially thought and should include a spectrum of outcomes outside of microcephaly alone. In addition, information from the research suggests that the risk of microcephaly is not only contained to infection in the first trimester.

According to the investigators in the EID study, surveillance for adverse pregnancy outcomes should begin the moment an outbreak is detected and should continue for 40 weeks after the outbreak is deemed over. In addition, the investigators found evidence that suggests that although the most severe adverse pregnancy outcome, microcephaly, is thought to occur only in the first-trimester infection of the virus, evidence suggests that after symptomatic infection in the mother, the risk of fetal injury remains throughout the pregnancy.

The investigators looked at data from 134 pregnant women who had presented with a rash and tested positive for the Zika virus. A total of 9 women were lost to follow-up and so the investigators were left with a cohort of 125 women, whom they followed throughout their pregnancy. A total of 58 adverse pregnancy outcomes were observed among the infants who survived. Microcephaly was observed in only 4 infants but was severe.

The investigators used mathematical modeling to “estimate the proportion of adverse pregnancy outcomes after symptomatic Zika virus infection at each week of gestation [in the women],” according to the study and then matched this estimate to the actual outcomes observed during and after the 2015-2016 Zika epidemic in 9 regions of Brazil.
What the researchers found was that instead of seeing the outcomes expected with first-trimester infection leading to microcephaly, that, in fact, the risk profile more closely matched models proposing elevated risk at all stages of gestation.

The investigators admit their study has several limitations, including the fact that they only examined a cohort of women who displayed a symptomatic infection with a rash, something that does not occur with all Zika virus infections. In addition, participants were only recruited from Rio de Janeiro, instead of all regions of Brazil, and, the “publicly available epidemiologic reports from Brazil recorded microcephaly cases, rather than all forms of adverse pregnancy outcomes,” according to the study.

Regardless, the authors feel that the results of their study suggest that, “when Zika outbreaks are identified, surveillance and planning for infection-associated APOs might need to focus on a longer period than previously thought.” They caution that the risk begins soon after the outbreak is detected, and further studies are needed to truly refine the risk of adverse pregnancy outcomes because of a Zika virus infection during gestation.
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Influenza A (H3N2) has caused most of the illnesses in this severe flu season, but influenza B is becoming increasingly responsible for more infections as the flu season continues to hit the United States.