Jan 26 2016

The Zika Virus

aedes mosquitoThe World Health Organization (WHO) and Center for Disease Control (CDC) are warning about yet another virus epidemic, the Zika virus. It may seem like such warnings are overblown, but they do need to be taken seriously.

Zika Virus

The Zika virus (Flaviviridae, an arbovirus) is spread through Aedes mosquito bites, the same mosquitoes that also spread Dengue fever. The infections themselves are usually mild, causing fever, rash, joint pain, and conjunctivitis. Many of those infected may even have a subclinical infection, meaning they do not notice any symptoms.

However, the infection can have complications. There is one case report of Guillain-Barre Syndrome (GBS) following a Zika infection. GBS causes inflammation of the lining of nerves resulting primarily in weakness with variable recovery. This does not appear to be a huge risk, but something to monitor.

The bigger concern is about pregnant women being infected. There are numerous reports of poor pregnancy outcomes, mostly microcephaly, in women who have been infected with Zika while pregnant. Microcephaly means small head, and results from poor brain development.

There is currently no treatment for a Zika infection (other than usual supportive care if necessary). There is also no vaccine.

A “Slow Pandemic”

Zika was first identified in Uganda in 1947. It spread throughout Africa, and then spread to Southeast Asia in the late 20th century. Recently it has also spread to South America and Mexico, with Brazil being a particular hot spot.

There are as yet no cases of locally acquired Zika in the US. There have been a few cases of people returning from travel to South America with a Zika infection. It is possible for Zika to become endemic in the US.

The virus can spread wherever there are Aedes mosquitoes, which exist throughout the Americas except for Peru and Canada. Interestingly, these mosquitoes were previously localized to the tropics and subtropics, but have been spread as invasive species by human activity – paving the way for later viral infections.

Zika is in the news now because the pace of spread has dramatically increased. It is no longer a “slow” pandemic, but rather is spreading rapidly.

What to Do?

As there is no treatment or vaccine for Zika, basic precautions are necessary. This mostly involves limiting mosquito populations and avoiding exposure. Mosquitoes breed in standing water, even small puddles or containers with water. Eliminating any standing water is therefore an important measure.

Ponds and lakes can also be sprayed. In the US, the CDC embarked on a campaign to eliminate malaria in the South through control of mosquito populations, and they were successful. So it is possible to reduce mosquito populations to such a degree that infections cannot spread – although malaria is not a virus, which may be more difficult to control.

Meanwhile, those living in areas with the mosquitoes can use repellent, keep their windows closed, use mosquito nets and take other measures to avoid being bitten.

The WHO and CDC are advising pregnant women not to travel to areas where there is currently an outbreak of the Zika virus. They are also suggesting that women who live in an area of an active outbreak might want to delay pregnancy, although they acknowledge this is a very personal decision.


There are a few lessons to be learned from the recent Zika outbreak. As a skeptical science communicator I find there is a delicate balance between giving people an appropriate warning without causing undue alarm. We are often in the position of pulling back overhyped fears. We also criticize the abuse of the precautionary principle.

The precautionary principle, properly applied, is legitimate, however, and sometimes there is a good reason for concern. Infectious disease is a real problem in our highly populated world with robust world-wide travel. The human population is essentially a breeding ground for bugs.

There have been serious pandemics in the past. Perhaps the most famous was the flu pandemic of 1918, which killed between 20-40 million people (more than World War I).

Also keep in mind that HIV was unknown before the early 1980s. This virus, which also came out of Africa, simmered undetected for many years then exploded, and is now a worldwide medical problem affecting millions. This one virus literally changed the practice of medicine.

We certainly don’t want to have another pandemic like the 1918 flu or another chronic infection like HIV. It is, perhaps, inevitable that we will, however. Bacteria, viruses, and other infectious agents evolve. Change is their major adaptation.

There have also been times when health organizations have issued warnings that then did not turn out to be a big deal, such as the bird flu and the swine flu. Do not let these incidents make you feel that the warnings were overblown. It is the job of the CDC and WHO to anticipate possible epidemics or pandemics and take measures to prevent or minimize them.

If they are functioning optimally there will be a certain number of false positives. False positives are far better than false negatives – missing or underpreparing for an epidemic. We therefore have to tolerate occasional false alarms and not let that make us cynical towards the next warning.

The Zika virus also is a reminder of the importance of world-wide control of infectious disease. We should be concerned about the spread of infections in the third world because it is the ethical and right thing to do. However, it is also important to recognize that we live in a world-wide community. When we allow infections to simmer in distant parts of the world, those infections might eventually work their way around to our part of the world. We are all in this together.

14 responses so far

14 thoughts on “The Zika Virus”

  1. carbonUnit says:

    Even in the temperate northern US, mosquitoes are a problem, carrying diseases like West Nile virus. Must be really bad in tropical climates. I’ve heard it said that mosquitoes don’t occupy any sort of important ecological niche. The world would do just fine without them. This Nature article for the most part agrees with that. I for one would be in favor of wiping the suckers off the planet if it were possible.

  2. GWD says:

    I have already heard from the conspiracy people that this is the next trumped up health crisis. Apparently this is the one that will create the NWO. The weird thing to is that at least in my circle these tend to be the same people who complain that these people don’t care about the developing nations. It is bizarre but at least people have something to complain about… I guess.

  3. LittleBoyBrew says:

    Time to roll out the DDT? I know that is a bit of a trolling comment, but it perhaps it might time to compare the potential risks of responsible DDT use versus the threat of Zika?

  4. mumadadd says:

    “Apparently this is the one that will create the NWO.”

    Is they an offshoot from NWA? 😉

  5. mumadadd says:

    *Are* they even…

  6. carbonUnit says:

    DDT is a pretty indiscriminate weapon. We can do better. Releasing large numbers of sterile male mosquitoes has a pretty devastating effect on a mosquito population and is nicely targeted. The mosquitoes can be sterilized via radiation, which can be tricky. Recent work involves GM mosquitoes. http://www.theguardian.com/sustainable-business/genetically-engineered-mosquitos-fight-malaria

  7. LittleBoyBrew says:

    carbonUnit: Yours is a good suggestion. Still in the early phase, but we should consider the facts of all options, or perhaps even better, combinations of options.

  8. RickK says:

    Interesting that nobody has mentioned the Olympics.

    Brazil is hosting both the Olympics and the Zika virus, and they’re already struggling with costs versus ticket sales for the games. How many people will be coming to the Olympics if it means tempting microcephaly in their next kid? Or, worse scenario – visitors to the Olympics take Zika home to several more countries.

  9. daedalus2u says:

    The epidemiology isn’t published yet, but I very strongly suspect that the zinka virus is only teratogenic during pregnancy. Many viruses are. Flu during pregnancy is associated with a higher incidence of schizophrenia (which is a reason why all women contemplating pregnancy should have their vaccinations up to snuff before hand). Rubella is also strongly teratogenic during pregnancy.

    There are relatively few viruses that produce a sustained infection that is not fatal. Chicken pox can produce a lingering infection that surfaces years later as shingles. Measles is either cleared, or it is fatal.

    Mosquitoes are important links in many ecosystems. Eliminating exotic mosquitoes would not have adverse effects. Many mosquito transmitted diseases are transmitted by exotic species (at least exotic in North and South America).

  10. zorrobandito says:

    So. The Zika virus was first identified in 1947, and has been endemic in Africa and Southeast Asia for decades. And yet it was only identified as a cause of microcephaly in October of 2015. Why is this?

    The analysis I read went as follows. First, there are a lot of things that can cause microcephaly, which in any case is a relatively rare condition. (Thank goodness for that!) By virtue of the fact that Zika has long been endemic in, for example, Africa, most women of childbearing age are already immune from past infection. So any surge in microcephaly cases would be relatively small, and any increase in the number of cases got lost in the “noise” of other causes.

    The spectacular explosion of cases (from 167 or so a year to about 4,000) occurred in Brazil when the virus was confronted with an immunologically naive population, a certain number of whom were pregnant women.

    I assume from this analysis, if it is correct, that the microcephaly effect will die down in due course, when everyone in the population has ample opportunity to become infected as children, long before pregnancy. The disease itself seems to be very mild; in fact in many cases there are no symptoms at all. So this problem sounds like it is on the way to solution in the long run almost no matter what we do or don’t do. The only task then would be to get through the short term with minimum damage.

    Of course this does not solve any problems the Olympics may be having as a result.

  11. mumadadd says:


    “The Zika virus was first identified in 1947, and has been endemic in Africa and Southeast Asia for decades. And yet it was only identified as a cause of microcephaly in October of 2015. Why is this?”

    That is spectacularly obvious now you’ve pointed out out!

  12. carbonUnit says:

    Just to clarify, since Steve brought this up on the SGU podcast, it is not necessary to wipe out all mosquitoes. From the Nature article I cited above: “There are 3,500 named species of mosquito, of which only a couple of hundred bite or bother humans.” We don’t have to wipe out all mosquitodome, just the suckers which cause us trouble.

  13. Teaser says:

    If you haven’t caught wind of this hypothesis please read. Of the articles I have read this is the best of the bunch.


    Has the GM nightmare finally come true?

    So down to the key question: was the Oxitec’s GM Aedes aegypti male-sterile mosquito released in Juazeiro engineered with the piggyBac transposon? Yes, it was. And that creates a highly significant possibility: that Oxitec’s release of its GM mosquitos led directly to the development of Brazil’s microcephaly epidemic through the following mechanism:

    1. Many of the millions of Oxitec GM mosquitos released in Juazeiro in 2011/2012 survive, assisted, but not dependent on, the presence of tetracycline in the environment.

    2. These mosquitos interbreed with with the wild population and their novel genes become widespread.

    3. The promiscuous piggyBac transposon now present in the local Aedes aegypti population takes the opportunity to jump into the Zika virus, probably on numerous occasions.

    4. In the process certain mutated strains of Zika acquire a selective advantage, making them more virulent and giving them an enhanced ability to enter and disrupt human DNA.

    5. One way in which this manifests is by disrupting a key stage in the development of human embryos in the womb, causing microcephaly and the other reported deformations. Note that as Melo Oliveira et al warn, there are almost certainly other manifestations that have not yet been detected.

    6. It may be that the piggyBac transposon has itself entered the DNA of babies exposed in utero to the modified Zika virus. Indeed, this may form part of the mechanism by which embryonic development is disrupted.

    In the latter case, one implication is that the action of the gene could be blocked by giving pregnant women tetracycline in order to block its activity. The chances of success are probably low, but it has to be worth trying.

    No further releases of GM insects!

    While I am certainly not claiming that this is what actually took place, it is at least a credible hypothesis, and moreover a highly testable one. Nothing would be easier for genetic engineers than to test amniotic fluids, babies’ blood, wild Aedes mosquitos and the Zika virus itself for the presence of the piggyBac transposon, using well established and highly sensitive PCR (polymerase chain reaction) techniques.

  14. Herm71 says:

    Long time reader/listener, first time commenter. Love your stuff. Came across this on FB and I smell a rat. No apologist for Monsanto, but, of course, some “health blog” has a post fingering Monsanto pesticides as the Zika culprit. I smell a rat. Any help?


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