Zika virus infection 2015-16 Epidemic
March 24, 2016 Update
Paul Herscu ND, MPH
Herscu Laboratory
If you have not yet read my first posting on this topic, please do so now before reading the following.
March 24, 2016 Update
Paul Herscu ND, MPH
Herscu Laboratory
If you have not yet read my first posting on this topic, please do so now before reading the following.
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. The specific variables I chose to focus on remain the same:
1. Will Zika virus impact the
USA?
2. Does Zika virus cause
neurological diseases or is it some other agent?
3. Is Aedes
aegypti the only vector we have to
worry about?
4.
How to address the intersection of economics and infections.
5.
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.
a. 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.
b. 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.
c. 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
