Zika Virus Update #2
Zika virus infection 2015-16 Epidemic
March 24, 2016 Update #2 (please read first posting here)
Paul Herscu, ND, MPH
As mentioned in prior longer posts, my intention was to lay a foundation and build scaffolding so that when you see data or hear the news or learn of novel discoveries, you will have enough history and adequate context to make sense of it and have an informed opinion, making it easier for everyone to both predict what the news will be, and to anticipate government and scientific next steps. And as I finished that post, I mentioned that if I did my job well, the next posts would be short as the scaffolding would be in place and the forecasts made, only needing to be confirmed. If you have not read those posts please do so, as they will help place the discussion in context. You can find them here and here. The specific variables I chose to focus on remain the same:
- Will Zika virus impact the USA?
- Does Zika virus cause neurological diseases or is it some other agent?
- Is Aedes aegypti the only vector we have to worry about?
- How to address the intersection of economics and infections.
- The role of Prevention.
Let’s dive in.
1. Will Zika virus impact the USA?
At the time of my original writing, CDC was mentioning that Zika virus would not impact the USA and if it did, it would be through sporadic isolated travelers bringing it back. I highlighted that that was incorrect and that the CDC in the next weeks would back away from those comments, and that Florida, Texas and potentially California, in the mainland would have local transmission. At this point, the federal government as well as those state governments have all conceded this points and are making plans for the prevention and treatment of the Zika virus. A more complete discussion on the spread including larger areas of the USA and is a much better model can be found in the first article below, and commented upon in the next three pieces.
I also mentioned that the national borders present their own problems in arboviral epidemics, and that issue will crop up shortly in discussions. Here is a recent example of that discussion in the popular press.
2. Does Zika virus cause neurological diseases or is it some other agent?
There were all sorts of discussions for a few months that the neurological symptoms seen were not due to this virus but instead were caused by any number of factors including pesticide use, false reporting, vaccinations, GMO mosquitoes, etc. I highlighted the reason that I thought that this was not the case, and that in the next months we would have definitive proof that this virus causes neurological problems. At this time we have gotten more of that proof in hand.
I had mentioned a retrospective trial that showed that in a prior outbreak, there was an increased incidence of Guillain-Barre syndrome. But science continued, and in a similar retrospective trial, this time found a 1% incidence of microcephaly associated with the infection in a prior outbreak. See below.
I mentioned that the reason only Brazil was seeing these neurological symptoms was that Zika arrived in Brazil earlier than the rest of South/Central America. We will begin to find neurological symptoms in those countries in the coming months after the virus makes its way to them. This is starting to be found in Columbia, Panama, etc.
I also mentioned that similar viruses cause similar infections; science is just now confirming our understanding of this. Towards that end, there were lab studies showing that the virus preferentially likes to settle in the nervous system and brain.
There is more, but at this point it is clear that this virus causes neurological damage in humans both temporary and permanent. It is also clear that Guillain-Barre syndrome and microcephaly are not the only neurological outcomes, as there seem to be other problems as well, with the developing fetus being most disturbingly at risk.
3. Is Aedes aegypti the only vector we have to worry about?
I brought up the topic that placing all our eggs in this one basket might be a mistake. Since that time others have raised their concerns. As mentioned before, other mosquitoes carried this virus in Asia, and Zika virus has been successfully introduced into other species of mosquitoes in the laboratory. More importantly, there are even questions raised if this is currently the only mosquito in place or if any Culex mosquito may also be the culprit. This is important since different mosquitoes have different life cycles, habitats etc, and therefore, the way we would deal with them would be different. A very interesting newspaper article is below. This remains a concern for me.
4. How to address the intersection of Economics and infections
I focused on some of the issues associated with poverty and epidemics. I thought a very enlightening take on this can be heard or read on NPR as below. Very clear, still focusing on why this is important to consider for anyone trying to understand, predict, and plan for epidemics.
5. The role of Prevention
This last point is the most important to me.
Our understanding, tracking, and contending with viruses is only at the beginning. I make this point whenever I talk about epidemics. When we are not aware of viruses, it is not that they are not there, but rather that we are in some sort of balance with them. That said, that is not always the case. As of today, I would like to highlight this very simple point with biology. In my first discussion with Zika virus, I placed it within the family where it resides, the family with Yellow Fever. And as of today, right now, there is an outbreak of Yellow Fever, another virus I mentioned from that family, in Angola, one that has killed 178 people in the past few months. It is the same small family of viruses producing problems for our species. And as interesting it is exactly the same mosquito, Aedes aegypti, that carries this virus in Africa.
And just to make the point a little differently, as we speak right now there is another virus injuring other species. Here, lambs in Ontario are succumbing to Chache Valley Fever. Most likely you never heard of this virus, which is one of my points. But here too most adult sheep get through the infection but fetuses may die in utero and be miscarried. Very rarely, though it does happen humans can get the same infection and they may develop meningitis or encephalitis.
I had already mentioned the other currently known infections circulating in the same mosquitoes in South and Central America, such as dengue fever virus, or chikungunya that are currently making many ill.
The point I am making is that we know this can happen with any number of viruses that you have or have not heard of. Mostly and luckily, it does not happen often. Rarely, sporadically, sometimes, it becomes epidemic. The question is what can we do now, for our patients, our communities, our families and those we love?
I think following what people do with Cache Valley Fever is a perfect example. One of the main ways to deal with this is to limit, as much as possible, the exposure of pregnant sheep to mosquitoes. That is the protocol. So, well, you get my point. Limiting exposure to mosquito bites, for now, has been, is, and must remain for the near future the most important thing one can do. Prevention must take center stage for every physician, public health official, parent, etc.! And I am sorry to say, but if you are reading this, you are probably lucky enough to be able to afford the preventive steps necessary to pass through this time. Preventing the bites not only protects one from one of these viruses but from all the other viruses the mosquito carries at the same time.
I want to end on a positive note. We, as a species have been around here for a very long time. In other words, as a species we have succeeded well enough. We are going to get through this. Remember, most people do not have any symptoms or only develop minor symptoms if they get the virus. Some very basic steps should make this not an overwhelming issue in your life.
The next update, to come shortly, will contain only preventive measures.
Until then, Don’t Panic.
Paul Herscu ND, MPH