In a Jan. 31 report, Newsweek is asking “What’s the chance of catching the Zika virus?” The answer depends upon where you live. The unasked question on many minds is “What are the chances that a Zika infection will hurt my unborn baby?” The answer to that question, at this time, is that public health authorities just do not know.
Brazil is the first place that concerns about Zika infections during pregnancy arose. A report from the AP dated Jan. 27 states that the government has received 4,120 reports of a serious birth defect called microcephaly in the period Oct. 22 through Jan. 23. Other media reports indicate that the Brazilians are noting an increase in a condition called Guillain-Barré syndrome (GBS).
AP states that the Brazilian authorities have investigated 732 of the 4,120 reports at this time. The review found that 63 percent were incorrect diagnoses and not microcephaly.
Brazil does not have a robust public health system for tracking conditions like microcephaly. A report published by the Centers for Disease Control and Prevention (CDC) on Jan. 22 notes that the official incidence of microcephaly published by the Brazilians was far less than that which would have been expected.
Basic statistical work using incidence rates from published studies and other authoritative sources suggests that Brazil has between 347 and 1,772 cases of microcephaly in an average year. If the ratio of investigated cases is applied to the reported 4,120 cases, 1,524 of them will be confirmed as accurately diagnosed.
Brazil has not released any data on the number of cases of Guillain-Barré syndrome. Columbia has reported 41 cases. El Salvador reports 46 cases.
Similar statistical work has been done to establish estimated levels of Guillain-Barré syndrome in those nations. In addition, all of the nations are already experiencing significant epidemic levels of dengue and chikungunya illnesses which can result in the syndrome. Brazil is also experiencing West Nile and measles that also can produce GBS.
There is not enough data to prove a link between Zika viral infections in pregnant women and microcephaly in newborns. The is also not enough data to demonstrate a link between Zika illnesses and Guillain-Barré syndrome.
Zika had been considered a relatively mild illness. The CDC states that about 80 percent of all those infected will have no symptoms. Those who have symptoms experience “fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache.”
Reports of the effects of a Zika infection do not equal confirmation. Many of the reports of microcephaly and Guillain-Barré syndrome are likely to be misdiagnoses. At this time, it is entirely possible that any confirmed cases are within norms and not an increase.
Travel warnings for pregnant women and other issued by the United States are “out of an abundance of caution.” Cases of Zika being diagnosed in the United States are imported, travel-associated cases, contracted overseas and diagnosed here. Until it warms enough for mosquitoes to emerge from hibernation, there is no chance of catching Zika in the U.S. Once mosquitoes are active, the number of imports “may result in local spread of the virus in some areas of the United States.”