Microcephaly and Zika Virus: Exploring Possible Factors for the Increase Prevalence in Brazil

Introduction: Recent studies have associated Zika virus with increased prevalence of microcephaly, abnormally small head circumference in newborns, among infants born in certain countries in South America. In the United States, data has shown that most states have maintained a high prevalence rate for microcephaly preceding the recent Zika outbreak. The question that has remained unanswered is whether the sudden increase in the prevalence of Zika virus in South American countries is truly attributed to bite of the female Aedes species of mosquito, or are other potential factors contributing to the increase. Several chemicals such as Pyrioxyfen, which was added to Brazilian drinking water for the first time in 2014 as a larvicide, is known to cause microcephaly. The use of such chemicals are controlled in the United States, but might not have similar regulations in other countries. Alcohol and drugs are teratogens that can cause microcephaly, the use of these substances are evident among certain ethnicities and countries (Mayo Clinic). Methods: Utilizing data on the prevalence of microcephaly in the United States a two-way ANOVA of the prevalence of microcephaly in certain racial groups by state shows a significant difference in the prevalence of microcephaly by race in each state analyzed. Results: The highest prevalence of microcephaly in the United States is in Alaska (19 per 10,000 live births), which does not have the Aedes species of mosquitos indicating that other factors are contributing to higher prevalence rates of microcephaly. Conclusions: Given that there several causes of microcephaly and the prevalence of microcephaly in the United States more research should be done to determine if chemicals such as Pyrioxyfen are the cause of the recent rise in the prevalence of microcephaly in South America.