The Zigzag Zika-Pandemic

28. June 2016
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Zika viruses continue their conquest of the world. Meanwhile WHO experts also see dangerous waters for Southern Europe. They have hopes for better diagnostics and innovative vaccines. A lot of time will come to pass before the emergency situation is under control.

In Central and South America the zika virus is being spread virtually unimpeded. More than 1.5 million people have been infected since 2015. Now more than 150 scientists are urging in an open letter to relocate the 2016 Summer Olympics. Already in early March Daniel R. Lucey and Lawrence O. Gostin, both from Washington, wrote in a technical paper [Paywall] that there is a threat of spread to other tropical countries. WHO experts shortly thereafter assembled an emergency committee and declared a “state of public health emergency of international concern”. Yet the crisis is far from over. More bad news followed.

Parts of Europe at risk

Zsuzsanna Jakab, WHO Director for Europe, as part of a recent statement on zika infections states her expectation of their being zika infections on our continent no later than by summer. In August, however, many thousands of people will be travelling to the 2016 Olympic Games – and will with their return flight be further dispersing vectors.

According to Jakab the island of Madeira and the Black Sea coast of Georgia and Russia will be particularly vulnerable areas. For 18 Mediterranean countries such as France, Italy, Spain, Croatia, Greece and Turkey, she rates the risk as “moderate”. For local authorities the only remaining action at present is to fight vectors such as yellow fever mosquitoes and Asian tiger mosquitoes. They also have plans to better inform citizens. Even repellents and instructions on proper clothing being issued are not quite enough, as current releases show.

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Worldwide spread of zika viruses. Quelle: Khamar / Wikipedia

Zika – join in

On multiple occasions over the last few weeks doctors reported sexual transmissions of the virus. Berlin’s Robert Koch Institute describes one German case. The patient got infected in the Caribbean and through unprotected sex infected his wife. She became ill two weeks after her partner did without ever having visited the critical regions.

Blood transfusions also come into the picture as an additional source of risk. Here we currently predominantly find individual cases. The need of the hour is to now better diagnose infections.

Better measuring

Currently, doctors determine the diagnosis predominantly via viral RNAs. In Central and South America six previously developed PCR assays are employed. But what about reliability? Is it possible to detect viral RNA even at very low concentrations? How sensitively do analysis systems respond to different zika-virus strains, and are their findings comparable to one another? Professor Dr. Felix Drexler and Professor Dr. Christian Drosten have now put PCR tests under the microscope. They work at the German Centre for Infection Research and at the University of Bonn.

Without supplementary serological diagnosis, 20 to 80 percent of patients are erroneously diagnosed, Drexler and Drosten write. Some systems were not sufficiently sensitive, others detected only certain strains. Antibodies are able to be diagnostically evaluated only after eight days.

Scientists fear that a large number of infections involving the virus are not recognised at all – a fatal situation for pregnant women. It is now evident that malformations of the brain of fetuses are associated with zika viruses. A team led by Patricia Beltrao-Braga from the University of Sao Paolo was able to show in animal experiments that zika viruses trigger intrauterine stunting. Michael Diamond of the Washington University School of Medicine in St. Louis figured out that the viruses initially proliferate in the placenta before spreading to the brain of the foetus.

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Scientists have demonstrated in a mouse model how zika viruses harm the fetus. Source: Miner et al., 2016, Cell.

This is just one more reason to optimise diagnostic systems. For this reason German researchers conceived two optimised PCR tests. They also describe options for calibration via synthetic RNAs. Nucleic acids from the laboratory contain different relevant target regions of the viral RNA. Drexler and Drosten have already provided their publication to the WHO in advance, in order to reach as many of our colleagues as possible. What’s more they offer their calibrator and their testing protocols worldwide for free. At the same time doctors have hopes for a vaccine.

Waiting for the vaccine

Brazil’s health minister Ricardo Barros now reports that development is progressing at a faster pace than expected. Laboratories at the University of Texas and Instituto Evandro Chagas in Brazil Pará are working closely together. After only nine months, ie. in November, Barros expects the first tests on monkeys and mice. He initially assumed twelve months’ lead time. The vaccine should be available on the market by 2018 at the latest, but that doesn’t help these patients and residents of vulnerable regions right now.

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