INTERVIEW: Tackling the Zika threat
pharmafile | February 9, 2016 | Feature | Manufacturing and Production, Medical Communications |Â Â Zika, vaccinesÂ
The Zika outbreak which started in Brazil and spread rapidly to other south American countries and beyond has taken the world by surprise and led the World Health Organization (WHO) to declare a public health emergency.
Evidence for a link between Zika and the birth-defect-causing condition microcephaly is growing and with the possibility of millions more infections before the end of the year, the pharmaceutical industry and others are beginning the difficult road to a vaccine.
Just what is the Zika threat and how difficult will it be to protect the population? Pharmafile.com spoke to Dr Edward Wright, virologist and senior lecturer in medical microbiology, University of Westminster, to get some answers.
PF: What is Zika and what is the link to microcephaly?
EW: Zika is a flavivirus of which not many people outside of the scientific community were aware up until a few weeks ago. People may have heard about West Nile, Dengue and Yellow fever, which are also flaviviruses of a similar family to Zika. What we know about Zika, we have accumulated in the past 70 or so years. It was first identified in monkeys in 1947 in a Zika forest in Uganda and this is where it got its name from.
Up until 2007, it was a relative unknown, even within the scientific community; it only caused a few cases of general flu-like symptoms and rash, and perhaps a bit of fever, but was not a serious illness and symptoms normally resolved within a week or so.
But in 2007, there was the first relatively large outbreak; just over 200 cases, in Micronesia, and in 2013 in French Polynesia, there were around 28,000 people estimated to have been infected. That was the first time where people have now gone back and identified this tentative link between Zika virus infection and microcephaly. This has hit the headlines in the last months or so, with the large outbreak in Brazil, which has now spread to other South American countries, where anywhere between half a million and one and a half million people have potentially been infected. And there is now a growing number of people reporting microcephaly in babies linked to the mothers being infected with Zika virus.
However, this is not clear-cut by any means. Just over 4,000 cases of microcephaly have been reported by the Brazilian government since the big outbreak started last year, and that is a 20-fold increase on the numbers reported in 2010. But it wasn’t until 2015 that microcephaly actually became a notifiable condition, and so we don’t have a baseline number of cases that you expect in a typical year to work from, and there isn’t the data yet to scientifically support that link between Zika virus infection in pregnancy, and birth defects. That’s what the money and resources announced after the WHO’s statement February 2 will be focused on answering.
PF: What can be done to control the spread while we wait for a vaccine?
EW: As the mosquito that transmits the disease is only found within certain countries in tropical regions where it is warm enough for them to survive, the virus cant circulate or be transmitted where this mosquito isn’t, and it won’t survive in a cooler climate. As a result, at the moment, infections are likely to be limited to tropical regions.
As for the number of infections, because at the moment, you don’t have a vaccine, it comes down to limiting the number of mosquitos in the area. You can use common mechanisms for doing this, such as spraying insecticide, and you can of course try and stop people being bitten. What was happening in Brazil prior to this outbreak was a trial of genetically modified mosquitos, which were produced by a company in Oxford. They produced self-limiting male mosquitos which were released. They then mate with females and their offspring will die while still larvae. These trials were for Dengue virus, which is transmitted by the same mosquito, and this trial was already ongoing. Results show that if you release these mosquitos, the number of mosquitos plummets by over 90% after six months, so it is very promising.
How easy will it be to create a vaccine, and does Sanofi’s work on Dengue and West Nile make it easier to create one for Zika?
You can certainly work with the information we have on the Dengue vaccine. There is also a West Nile DNA vaccine in development. We can learn from the experience with those two viruses, as they are so closely related to Zika, and adopt similar approaches. We don’t know that the outcome would be similarly promising, but unlike Ebola, where we had vaccines that had undergone the basic laboratory tests and even undergone animal testing, and were ready to go into clinical trials, we are not even at the laboratory testing stage with Zika, and indeed have nothing to test in the laboratory! So we are several stages behind where we were with the Ebola vaccine, but the information we do have on Dengue and West Nile will be used be the people who are looking at developing vaccines, to try and decide on the mechanism that will have the best chance of producing a vaccine for Zika that will give us the immune response needed to provide protection.
Because there wasn’t the number of people getting infected, it has not been seen as commercially viable, and drug companies were not going to put money into it. I think after the experience with Ebola, and now with Zika, people are not saying we are going to invest in the research needed to develop the basic information needed for vaccines and treatments, and also the infrastructure to make sure they can be manufactured to a high enough quantity.
A case of sexual transmission of the virus was reported in early February. How much of a concern is this?
Indeed, there was a report of sexual transmission of the virus in Texas. We were actually aware the disease could be transmitted in this way before this, as there was another potential case where a researcher had gone to Senegal in 2008, developed flu-like symptoms, and come back to America, and a few days later, his wife developed similar symptoms. They were both tested and both came back positive for Zika. And the wife hadn’t left America. So there are a couple of documented examples of this infection, but what you have to bear in mind is at the moment, there are around a million potential cases of Zika infection. We can’t be 100% sure they are all mosquito-transmitted, but it’s highly likely, and we only have two cases of sexual transmission. So the additional risk of sexual transmission seems very low, but this is something we’d need to get a better handle on.
We don’t have very good epidemiological or clinical data on possible Zika infection, but this is what people are now working very hard towards- getting a better idea how many are infected, how many of those are pregnant women and what was the outcome for their babies. We need to understand what threat this virus poses before we go too much further forward. Has the virus mutated, has it changed? Is that why we are seeing so many cases in Brazil? Has the mosquito that carries it changed and become more effective at transmitting it? These are the questions that people are trying to answer. We will learn a lot more about Zika in the coming weeks and months.
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