Six things you need to know about Zika right now


The Zika virus situation is this year’s Ebola. Like with Ebola, a lot of doom and gloom is floating around, and a lot of outright lies are being put forth by people who have no clue of what is going on. They are relying on fears and speculation to drive up visits to their websites or blogs because clicks pay in today’s internet economy.

Not on this blog. If you look around, you’ll see that I am not selling you anything. I’m not advertising for anyone, and I will resist every urge to do so. If I were in the business of making money, I wouldn’t be in Public Health. My profession is notorious for under-paying people in it, unless you manage to land some big-time consultancy or an academic position.

With that in mind, I want to tell you some things you need to know about Zika right now, and some things you need to keep in mind as we move into the warmer months of the year here in the United States, or if you’re traveling abroad. Just like with all emergencies, be informed and act, but don’t get consumed by it all. Most of all, don’t panic.

  1. Zika is a viral infection caused by — you guessed it — the Zika virus. The Zika virus (or ZIKV as some are calling it) is a relative of Yellow Fever, Dengue, and West Nile Virus. Like its cousins, Zika is transmitted by mosquitoes.
  2. The species of mosquito that is primarily distributing Zika around the world is the Aedes species of mosquito. Currently, in South America, it is the Aedes aegypti mosquito that is doing most of the transmission. This Aedes species also transmits Chikungunya and Dengue. In the United States, we have the Aedes albopictus species more than A. aegypti. That doesn’t put us in the clear, however, as A. albopictus has been associated with Zika outbreaks in the past.
  3. It is generally a good idea to avoid being bitten by mosquitoes, whether here in the United States or in a tropical area, or in Europe. It doesn’t matter. Avoid being bitten by mosquitoes, flies, ticks, and other insects/arthropods to maximize your chances of avoiding Zika and other arthropod-borne infections. Avoid areas where there are a lot of mosquitoes, wear long sleeves and long pants if you must go to those areas, wear repellents, drain any standing water near or inside your home, etc. Do what you need to do to prevent mosquito bites and control their population. But be smart about it. Don’t think that because your town government fogged for mosquitoes that somehow you’re protected. You might not be.
  4. As of today, Wednesday, February 17, 2016, there has been no causal link between microcephaly (a reduced size of the head at birth) and Zika virus infection during pregnancy, but there is compelling evidence that there is a link in there somewhere. A few days ago, an activist group from South America came out with a position that it was a larvicide (a chemical added to water to prevent mosquito larvae from maturing) that was causing the microcephaly seen in places where there is heavy Zika infection rates. This is nothing more than a conspiracy theory at this point. In fact, the evidence against the larvicidal is flimsier than the evidence for Zika causing microcephaly. That is, if we are to believe it’s Monsanto and the evil corporations causing microcephaly, then we must accept that it’s Zika because the evidence for Zika causing it is more coherent.
  5. There is a lot yet to learn about Zika, shamefully. And I write “shamefully” because Zika has been hitting places far from the United States for a while now, and it is only now that it is at our doorstep that we are panicking into doing something about it. We really are panicking. You see the panic in politicians who are, like they did with Ebola, calling for strict quarantines of people traveling to places where Zika is being actively transmitted. (As if mosquitoes can be quarantined.) And you see the panic in the increased response from the Centers for Disease Control (CDC). They are pulling a lot of resources from a lot of places, yet duplicating a lot of the work that has already been done by public health agencies in other countries. (It’s not good enough until Americans do it, I guess.) Had we done all this when French Polynesia got hit in 2013, we might have avoided Zika from reaching Brazil. Had we done it before that, we might have contained it SE Asia.
  6. So stay informed on the situation by frequenting the WHO News/Media Center or the CDC Zika Web Page. If you want opinion, you can come to this blog, or Orac’s, or the Public Library of Science’s Neglected Tropical Diseases page, or the Virology Blog. Don’t panic. You’re going to be okay. We all are.

12 Comments on “Six things you need to know about Zika right now”

  1. Doctor Kenneth Camargo Jr., MD, PhD covered this very subject, in detail and even mentioned how the same larvicide has been in use in Argentina for five years or so. It’s over on “Scientific Parent”.

    Zika!!!! Run, Hide, it might get you! And give you a rash.
    Why didn’t we react to the hemorrhagic fever Dengue, back when it flared in Florida? At least with that one, a different strain, on a subsequent infection could be lethal.
    Oh, it wasn’t an election year, so panic wasn’t being sold wholesale.

    And those jackasses want to be president?! Quarantine Christie, someone one should ask for advice, then do the precise opposite in order to be correct, the rest follow his mislead.


    • My bad, the larvicide has been used in Columbia since 2010. Shouldn’t we have seen larvicide “damage” by the end of 2011?
      Oh wait, humans aren’t insects and the dose to cause problems is immense. Greater than 1 mg/L of water. A lot greater.

      Liked by 1 person

  2. Am I the only one who has noticed that the references Camargo links do not support his claims?

    See the part: “This is incorrect: Cases of microcephaly were retrospectively detected in Polynesia. Additionally pyriproxyfen has been used in Colombia since 2010 so if pyriproxyfen was the cause we’d expect to see the same increase there in 2010 and 2011, but that hasn’t happened.” None of the 3 links seem to back up his claims, unless I’ve missed something.

    I’m also suspicious because of the incredible sloppiness with which the larvicide hypothesis is being dismissed by almost all the sources I’ve seen. Talk about safe dosages based on toxicity rather than developmental sensitivity, lack of statistics by region, lack of statistics about background rates of microcephaly in those regions before zika, claims of “use” which do not discriminate between use as a spray and use in drinking water, lumping of the larvicide hypothesis with conspiracy theories, etc.

    (BTW, I was skeptical here about low infectiousness of Ebola, and you were right. I like to admit when I was wrong.)


    • For the larvicide theory, I like to begin with biological plausibility. Humans are not mosquitoes. We don’t have the hormone targeted by the larvicide. So the larvicide is biologically inert in us from that angle. (The “doctors” claiming it was the larvicide said that the larvicide stunts development of mosquito and that microcephaly is stunted human growth so it must be the larvicide.)
      Next, it’s not just Colombia that has used the larvicide. It’s other countries as well, including the United States. No microcephaly increases.
      Now, we could take it a step further and ask, “But what if it got used in tremendous amounts in only those places in Brazil?” There is no evidence of that. Not even the concerned group has been able to back it up. And, while the increase in microcephaly is huge, it’s not as huge as one would expect from a population-wide exposure from an ubiquitous source like water.
      As for background rates, this has been looked at as well. Look at the slides from 12:48am to about 12:55 by Dr. Espinal from PAHO on these notes I kept from a presentation at Hopkins:

      You’ll see that there were a few cases per 10,000 residents between 2010 and 2015, then Zika arrives and there is an explosion of cases. Also, the epidemiological pattern is that Zika arrives, GBS and other neurological conditions appear at the peak of the epidemic, then the epidemic slows down and microcephaly cases appear. The pattern is starting to repeat in Colombia, with neurological cases appearing. If the pattern holds true to what was seen in French Polynesia and Brazil, then the microcephaly in Colombia comes in June.
      I hope we’re all wrong. I’ll take the hit in the epidemiological ego over kids with microcephaly any day of the week.


      • Thanks for the quick response. But I find it unsatisfactory because it does not adequately address a number of issues.

        First, NOBODY claimed we had the hormone targeted by the larvicide. So that does not in any way make the theory implausible, because the larvicide could be affecting something else in developmental pathways, THE SAME WAY Zika supposedly affects something in developmental pathways. The same way thalidomide did.

        Second, the word “used”. There are different types of uses: spraying versus adding to the water supply. Some would result in more ingestion than others. I see no references to use in water supplies outside of Brazil yet. So spraying or other “use” in the USA is not the same as adding to the water supply, and a failure to see microcephaly in the US could be easily explained by different exposure. This is the type of sloppiness in dismissals that I complained about.

        Third, claims of low background rates may not be reliable because of less attention to diagnosis and reporting prior to the Zika scare. Consider the vast increase in reporting of autism in the past few decades, for example. However, my gut feeling is that the increase is real.

        Fourth, Espinal considers the chemical hypothesis, and points out that it is far too early to choose any hypothesis as right.

        Fifth, conflating GBS with microcephaly makes no sense. We could easily be seeing GBS from Zika and microcephaly from the larvicide. Columbia doesn’t show sufficient microcephaly cases yet to associate microcephaly with Zika. Nor does any other country except Brazil.

        And finally, you haven’t responded to my point about Camargo: I’d be interested if you agree with me that his links do not back up his statements.

        “I’ll take the hit in the epidemiological ego over kids with microcephaly any day of the week.” I find that truly admirable. Likewise.


  3. First, yes, the larvicide could be affecting something else. So could a new ingredient in potato chips. Heck, we all could have been recently irradiated by gamma rays and changed in such a way that we now have the hormone that the larvicide attacks. If we’re going to deal with probabilities, and with very small ones at that, then we might as well call it a wrap and off ourselves.

    Second, if you don’t see references to the larvicide being used outside of Brazil, “used” in any way, then you’re not doing your due diligence in investigating this fully. I am not here to do your homework for you.

    Third, the claims of low background rates are reliable. Period. Again, you fail to do your due diligence and understand that Brazil has one of the most advanced maternal monitoring systems, a leftover of the days of smallpox eradication. They keep a very good eye on their pregnant women and the newborns. Their system is solid, even more solid than that of the United States. But, again, I’m not here to do the research for you.

    Fourth, sure.

    Fifth, as in the first, we could be seeing it from all sorts of other things. If you want to focus and not let go of the low probabilities, that’s up to you. As explained before, Colombia won’t see the cases yet — and probably not until June — because of the way that this is playing out epidemiologically. If you so desperately want cases in Colombia, a flight down to Barranquilla from Miami is about $500 both ways. Feel free to go find them yourself instead of believing what the experts are saying.

    Finally, I could care less about Camargo. I have better things to read than yet another debunking of a very flawed and hysteria-filled theory.


    • I was hoping for a less snotty response.

      First, I was complaining about dismissal of the larvicide hypothesis for an INVALID reason, that we haven’t the same juvenile hormone. Whatever mechanism Zika might affect in development could be instead perturbed by the larvicide. Nobody knows yet, and it is not obvious that one is more likely than another.

      Second, you did not read me carefully enough: I haven’t seen references to the larvicide being used in WATER SUPPLIES outside of Brazil. I could easily be wrong here, but dismissals that don’t cite usage in water supplies outside of Brazil are not backed by evidence.

      Third, I’ll accept your claim that measures of background rates in Brazil are reliable.

      Fifth, your argument here is pure snottiness. And I happen to be an entomologist in Ecuador (next to Columbia) assisting at the public health service INSPI (in a very minor, unpaid role), so I am very interested (though I make no claims to any epidemiological expertise.)

      Finally, my point has been that Camargo is only one example of the incredible sloppiness of dismissal of the chemical hypothesis, one that happened to be promoted in your comments. I’ve seen such sloppiness before in denialist propaganda about environmental problems, usually funded by industry. This makes me very suspicious because of the commercial and political incentives to evade blame if the larvicide is actually causing the microcephaly. Have you ever read “Doubt iIs Their Product” or the numerous other books detailing corporate disinformation projects? As an epidemiologist you should know all about the histories of tobacco, lead and asbestos, for example. The same thing could be going on now. Alternatively, it could actually be caused by Zika: it is just too early to dismiss the chemical hypothesis from what little I know and the universally bad arguments I have seen so far. I would be very happy to be convinced otherwise when I see sound epidemiological argument. Please point me to some.


      • Thank you for caring about the tone of my response more than the substance. I have a hard time believing that you’re anywhere in South America right now because you keep misspelling Colombia. I’m also not going to go through step-by-step and answer you any more. There’s just no point. You want to believe that corporations are lying, that the larvicide is being used in more ways than one, and that there’s something to the theory that it is the true cause of microcephaly. That’s your right. Unfortunately for you, and fortunately for me, I have other fish to fry than to sit and wonder about very small probabilities and very, very small possibilities. For example, it is probable that Monsanto deliberately released the larvicide to the world years ago with an eye to Brazil this year in order to create an entire generation of microcephalic children that will work as slaves for the production of GMOs. But it’s more probable that Zika, which has shown in French Polynesia to cause neurological damage, and now in Brazil, and soon in Colombia (though I hope not), is the cause of all this. So, before I recommend to anyone that they remove a larvicide which has been shown to reduce mosquitoes and prevented malaria, Chikungunya and Dengue, I’m going to recommend an all-out assault on mosquitoes instead.


        • I can think of one step in fetal development where Zika could wreak havoc, indeed, fetal alcohol exposure can and does wreak similar havoc in the same period of development.
          Meanwhile, as you said, we’re not insects, we don’t share the same developmental hormones and signal molecules for development.
          Indeed, to see a closer similarity, one has to approach the humble frog, who shares a similar signal pathway in development, which for both species, switches gills to lungs – thyroid hormone and prolactin.
          Interestingly, both hormones are conspicuously absent in insects.
          Indeed, for insects, I have a handful of items around the house that are lethal to them. Boric acid, used by humans as eye wash, is lethal to many, many species of insect. Diatomaceous earth can and is swallowed by mammals, such as cattle, cats and humans, which can clear several forms of parasitic worm infections, but are absolutely lethal to insects.
          Then, there’s soap. Harmless to most vertebrates, lethal to insects, eggs and some stages of insect life.
          In the quantities used, larvicide can only cause one a problem if one is a maggot.
          For, it is true, the dose makes the poison and mommy dilutes the dose, which was already massively diluted.
          It’s like complaining about oxygen being toxic, so we should get rid of all of it. All because pure oxygen can and is harmful at STP. Meanwhile, ignoring that between 6 – 10% oxygen levels cause unconsciousness.Excuse me while I get some hydroxic acid.


      • This is the problem with the larvicide hypothesis. The best biological plausibility anyone can demonstrate boils down to “well, we don’t know it doesn’t cause microencephaly”. Which is a piss poor argument. For zika virus we have evidence that it can cross the placental barrier and it has been found in neonatal neural tissue.

        What you don’t understand about that is beyond me.


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