Public health systems and the Zika virus

Zika virus has been covered in the press, and I have been tempted to leave it to others, but it may be interesting to get down in the weeds and ask how public health officials and virologists are responding. Does Zika virus have an Achilles’ heel? Can we learn from related viruses?

Zika virus is an arbovirus, for arthropod borne virus, which means that it is carried by mosquitos and ticks (both arthropods). Mosquitos, particularly Aedes aegypti, are their air force, seeking and injecting the viruses into humans in exchange for a little blood. Ebola, fortunately, was not an arbovirus. Zika infections in Brazil may have now passed one million. There is huge worry about Puerto Rico, which is also facing a financial crisis and shuttered medical facilities. Aedes aegypti has spread into 30 U.S. states, according to the Centers for Disease Control (CDC), although these mosquitos do not all carry the virus. If Zika virus finds a cold-tolerant mosquito species to carry it further north, it could become a major problem for everyone in the U.S. 

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The best approach to any disease is to marshal the tools of public health: killing mosquitos and other vectors, removing standing water where mosquitoes breed, using repellents and using screens. Best would be a stock of reliable vaccines. I have never seen a TV drama that features public health workers heroically tracing the contacts of infected people to stop the spread of a disease (I grant you a few good films: “Contagion” and “Arrowsmith”). Public health workers don’t usually have soulful moments with patients, so it doesn’t make good TV, and it does not excite congressional committees. Requests to appropriate $1.9 billion to confront Zika virus have gone nowhere yet. Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Disease at the NIH, is shifting money from other programs. 

Vaccine production companies have little economic incentive to make new vaccines for which poor nations cannot pay. Viruses find a way to spread, and therefore we can’t avoid trying to produce vaccines for threatening viruses. Even if they did not, there is an obligation to help other people. New public-private partnerships may be needed. (One such partnership has recently produced a drug to inhibit the Ebola virus, but that is another subject.) An article by Jon Cohen in the January 1, 2016, issue of Science Magazine titled “Unfilled Vials” lists the 10 top diseases for which we could stockpile vaccines but have not. Zika was not included, but would now have to go high on that list.

The Zika virus genome is made of a relatively short length of RNA, a close relative of DNA. It is a so-called positive strand RNA virus — once a Zika virus particle is inside a human cell, it sheds its protein coat, and the single strand of RNA takes over the human cell’s machinery and makes more virus components, which assemble into many viruses, kill the cell, and spread. See: wikipedia.org/wiki/Zika virus for an animated video.

A virologist receiving a blood sample from the field would immediately determine the RNA sequence of viruses in the sample and would quickly learn that the sample contains Zika virus. Scanning the computer data, he or she would immediately notice that the new virus was related to yellow fever virus, West Nile virus and dengue fever virus, all positive-strand RNA arboviruses. According to my information from the NIH, these viruses even look alike down to the level of atoms. 

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Knowing Zika virus’ surprisingly close relatives opens opportunities. Dr. Stephen Whitehead and his team at NIH’s National Institute of Allergy and Infectious Diseases (NIAID) have made a dengue virus vaccine. The vaccine or a placebo was given to a group of volunteers, and a month later they all were challenged with a mild dengue virus. None of the vaccinated people had symptoms, but all of those who received the placebo got sick for a few days. None of the scientists knew who got the placebo or the vaccine until the experiment was over. 

There is a very effective vaccine for yellow fever, and one is being developed for West Nile virus, so a Zika virus vaccine is possible. I wonder whether people who have had a Zika virus infection have high levels of antibody against the virus in their blood? They probably do and may be immune. Would it be safe for a woman in Brazil or Puerto Rico with such antibodies to get pregnant? In any case, Dr. Whitehead and the scientists at NIAID are working on a Zika vaccine. Call it: Your Tax Dollars at Work.

Richard Kessin is professor of cell biology and pathology emeritus and special lecturer at Columbia University. He lives in Norfolk and can be reached at rhk2@columbia.edu.