As more scientific attention focuses on Zika virus and why we’re seeing neurological damage now in this outbreak when we hadn’t in previous outbreaks, new information is constantly coming to light. I wrote a previous article looking at the possible link between the microcephaly being seen in Brazil and a larvicide being used in drinking water. While I personally didn’t field a ton of comments on this article, I saw numerous places on social media where folks compared the questioning of the possible link between the microcephaly cases with the larvicide as akin to the anti-vaxxer movement. I just wanted to take a moment to point out the need for healthy skepticism when an infectious agent suddenly begins to cause previously unknown damage in humans. Significant mutations in how a virus interacts with it’s host are relatively rare; and while they shouldn’t be discounted, mutations shouldn’t be the only answer considered. While vaccines are designed for and tested extensively in humans since the human immune system the intended beneficiary of vaccines, larvicides and pesticides are designed to kill larvae and insects, they are not designed to have a biological benefit to the human body. At best their effects on humans are null, at worst they cause damage. Anyone remember a little chemical called DDT, previously used all over the place and in large quantities to control disease causing insects, that is now banned in many countries due to its negative effect on human health? Scientists probably didn’t foresee the negative impact on humans, but eventually it was discovered and then that chemical was no longer safe to use. A healthy dose of skepticism allows us to consider all possible explanations before immediately assuming that something that wasn’t really intended for human consumption but previously deemed “safe” is indeed safe and that significant, relatively rare viral mutations are obviously to blame (or whatever other ideas are floating around).
Now that I’ve cleared that up a bit, on to the new information regarding Zika virus.
The link between Zika virus and microcephaly grows stronger.
A study published in the New England Journal of Medicine looked at Zika virus infection in pregnant women in Rio de Janeiro. The study compared 42 infected pregnant women with 16 uninfected, healthy pregnant women who all lived in the same area. The authors found birth defects, including microcephaly, in 29% of the infected women, and no birth defects in the uninfected women. The women got infected with Zika virus at various stages of their pregnancies. The fetal abnormalities were found in the fetuses regardless of what stage of pregnancy the women were in when infected. While first trimester infections are generally resulting in more severe abnormalities, the fetuses of women infected as late as 27 weeks gestation still had central nervous system abnormalities. Only a few women from this study have given birth so the conclusions are still preliminary. While this study was small in scale, it points to the link between Zika and serious fetal development issues, including but not limited to microcephaly.
Colombia seeing first cases of birth defects possibly linked to Zika
Colombia’s Zika virus outbreak started later than Brazil’s, so infected Colombian women are just starting to give birth. So far three babies born with brain abnormalities all tested positive for Zika virus, according to an article published in Nature. Because Zika got to Colombia after Brazil, scientists and researchers in Colombia know about the link to fetal abnormalities and are putting measures in place to closely monitor pregnant women to help establish the magnitude of Zika’s impact on fetal abnormalities. Colombia had national tracking programs set up as of last December to monitor women for signs of infection and to spot early signs of abnormalities in fetuses. The Colombian Collective Network on Zika (RECOLZIKA), a network of researchers and public-health institutions across Colombia, are already investigating a few other suspected cases of microcephaly, with possible links to Zika. RECOLZIKA plans to establish baseline birth defect numbers in certain areas to get a true sense of the increase in birth defects due to Zika.
Zika linked to paralysis disorders, not just birth defects
Previous outbreaks of Zika virus had linked it to Guillain-Barre Syndrome, an illness where the body’s immune system attacks and damages nerves causing muscle weakness and sometimes paralysis. A study published in the Lancet looked at the outbreak of Zika virus that occurred in French Polynesia during late 2013 to early 2014. This study found that of the 42 people who were diagnosed with Guillain-Barre Syndrome (GBS) during the study period, 41 of them had antibodies to Zika virus (indicating a previous Zika virus infection). 88% of the participants reported a transient illness about 6 days before GBS symptoms appeared, suggesting recent Zika virus infection. While this study is small, it does provide additional evidence linking Zika to GBS and demonstrates that healthcare professionals and public-health workers should be looking for GBS symptoms as well as birth defects.
Zika has recently been linked to a third disorder: paralysis-causing myelitis. According to a case report published in the Lancet, a 15 year old girl on the French Caribbean island of Guadeloupe was diagnosed with the neurological disorder “acute myelitis” (an inflammation of the spinal cord causing paralysis). Doctors found high levels of Zika in her cerebrospinal fluid, blood and urine. Other potential causes of myelitis including chicken pox, herpes, and others were ruled out. The girl has since recovered from her illness. Viruses related to Zika, such as dengue, Japanese encephalitis, and West Nile, have well-documented links to neurological disorders. While this was only one case, it demonstrates that Zika virus infection may not be as benign in adults as previously thought.