Why Science Cannot Prove Zika Virus Causes Microcephaly

Zika virus, the illness linked to increased incidences of microcephaly and Guillain-Barre syndrome, has been the topic of mainstream media for months. Given the magnitude of the health issues thought to be associated with this virus, why hasn’t science yet determined the answers?

Background of Zika Virus

Until the recent Zika virus outbreaks in the Americas and Caribbean beginning in late 2015, it was an obscure tropical illness. The virus is not a new one, having been discovered in 1947 in rhesus monkeys in the Ugandan Zika forest. It wasn’t until twenty years later that the first infections in humans were reported with those cases occurring in Nigeria.

The illness remained confined to equatorial Africa and western Asia until 2007 when an outbreak of Zika virus was reported on the isolated island of Yap Island in Micronesia. There, 108 cases were confirmed with no one having symptoms beyond that of a mild illness.

An outbreak beginning in 2013 on 15 islands in French Polynesia including Bora Bora and Tahiti resulted in 27,000 confirmed cases, again with no reports of symptoms beyond a mild illness.

How Zika Virus History Affects Determining Cause-and-Effect of Birth Defect and Neurological Conditions Currently

Diseases generally follow a predictable path or progression, rather than jumping from being a mild illness to that of one capable of causing an increase in the rare birth defect of microcephaly in newborns or Guillain-Barre syndrome in others.

Until an isolated case eight years ago, the only known transmission of Zika virus was from the bite of an Aedes mosquito carrying the virus. Eight years ago, there was circumstantial evidence of human-to-human transmission of Zika virus when a researcher from Colorado returned home from field work in Senegal. His wife became ill with Zika virus after her husband’s return home, although none of their four children contracted the illness, leading to the conclusion that it was through the exchange of bodily fluids – most likely sexual activity – that allowed the transmission from husband to wife.

Currently it is known that Zika virus is present in urine, saliva and semen. On Feb. 2, 2016 the CDC confirmed transmission of the virus through sexual activity in Texas, where a man who returned from a trip to Venezuela, a known site of active Zika infection, returned home to Texas and transmitted the illness to his partner.

As Dr. Stephen Thomas, an Army colonel and virus expert at Walter Reed Army Institute for Research explained, “I am trying to understand why what we are seeing in Brazil we haven’t seen in 30 years of circulation in Southeast Asia (and elsewhere).” (NBCNews.com)

Might there have been earlier cases of Zika virus transmission through sexual transmission or otherwise, but because the illness was of such a mild nature – and only 20 percent of people infected with the Zika virus actually developed symptoms – no one delved any further than the known mosquito transmission.

Current Data Is Too Inaccurate to Be Reliable

Scientific research and the conclusions it reaches are dependent on accurate data on which to base the research. The current data with which the scientists have to work is questionable at best. For instance, health authorities in Brazil reported more than 4,000 cases of microcephaly since November 2015. When these cases were further investigated, it turned out that only 270 of those cases were both microcephaly and related to a Zika virus infection in the mother.

Should Health Care Be Testing Blood, Saliva or Urine to Confirm Zika Virus Infection?

Health authorities have been relying on the results of blood tests to confirm an active Zika virus infection, even though researchers confirmed that it was easier to detect Zika virus in saliva than in blood during the outbreak of the illness in Tahiti in 2013-2014. At that time, blood testing of symptomatic patients found the virus 28 percent of the time, while saliva testing in the same patients found the virus 57 percent of the time.

Does this difference in the accuracy of testing mean that Zika virus infections may have been under-reported through the decades? The mild symptoms suggest that many people with the illness may never have sought medical care. Since only 1 out of 5 persons with the Zika virus infection actually develop symptoms, how many of those without symptoms have gone undiagnosed? Those numbers are likely staggering, and because the infections went undetected, any resulting side effects of the infection such as microcephaly or Guillain-Barre syndrome — or any other issues?

In Summary of “Why Science Cannot Prove Zika Virus Causes Microcephaly”

As Melinda Moore, a pediatrician at the RAND Corp. explained, “There’s not going to be any single perfect piece of data to link Zika to microcephaly,” referring to the mounting circumstantial evidence between Zika virus and the birth defect. What will be required will be the acquisition of multiple pieces of imperfect evidence to show a chain of irrefutable science proving or disproving what is now assumed. (FiveThirtyEight.com)

Health Tips by Deb DVN graphic for Health Column

Health Tips by Deb

Sources: NBCNews.com

HealthMap.org

FiveThirtyEight.com

 


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