APRIL 26, 2016
Zika Virus (ZV) disease manifests as actual illness in only about 20% of those infected. That fact alone makes it a difficult situation, since there’s no knowing if you’ve acquired the virus in an exposed area. Only blood tests can determine that. The good news is that if you get ZV, you will at most have a illness for 2-7 days. The bad news is that if you are sexually active and of childbearing age, such exposure may pose a risk to your developing child for a yet unknown time, though at least as long as 10 weeks per a recent case.
ZV is thought to have emerged in Uganda, Africa around 1920 and made its outbreak debut in 1947. Populations in Africa and Asia have shown evidence of widespread infection by blood tests.
During 2014-2015, joined to international attendees of the FIFA Soccer World Cup Games, ZV exploded throughout Brazil, and then Colombia. It now occupies much of South and Central America and the Caribbean, soon to arrive in the Southern United States.
Why? Because there are no ecological or epidemiological barriers. The former refers to the Aedes aegypti mosquito vector that carries ZV which resides throughout the Americas and Carribean, and up into lower California, Arizona, New Mexico, South Texas, and Florida. “No epidemiological barriers” means that for our population (and our southern neighbors), there is no pre-existing immunity… it is a “novel virus”. Our part of the human herd has not experienced ZV, the key circumstance for rampant spread in the next few years. With the large influx of illegals across the southern border, ZV will be imported by people who have not even been clinically ill. Once our mosquitoes feed on them, person-to-person spread will be established and our resident mosquito population permanently an infected reseviour. This phenomenon of a massive virus disease outbreak was most recently seen a couple years ago with the African, multi-national Ebola pandemic, largely attributed to social unrest and civil war, and so disruption of sovereignty of bordering countries by uncontrolled immigration and emigration of their populations.
So far, U.S. cases have all been imported by travelers to Zika disease (ZD) areas. But, as we now enter mosquito season in the South, look to explosion in incidence across the country. It is unclear how restricted to the South all this will be. The Asian tiger mosquito, Aedes albopictus, ranges from the U.S. South to as far north as New York State, and it has been shown to be a vehicle for ZV.
We have seen “novel” viruses before. The Spanish Flu of 1918 caused a worldwide flu pandemic accounting for 50-100 million deaths (5% of the world’s population then) over a few years. It was a mutated virus which human immune systems had not “seen” before. Fortunately, ZV does not have that virus’s destructive potential. However, the “novelty” of this virus will be the tale of the next few summers as mosquitoes emerge, and it will be felt most by the developing unborn.
This may be the most important part of the commentary and I have not seen the current Zika knowledge base developed into these ideas anywhere.
Zika virus infection is not experienced as a clinical illness (symptoms or physical signs) in about 80% of those infected. Last week a woman infected in Guatemala was found to have the ZV in her bloodstream 10-weeks after she first acquired it. She was pregnant and it is unclear whether the ZV just remained in her bloodstream the entire time, or whether it was cleared by her immune system and then entered a secondary phase of bloodstream infection by way of her infected fetus’ placenta infection. Either way, ZV sustained for a very long time in the bloodstream without observable illness– similar to HIV, hepatitis C virus, and hepatitis B virus (after the initial, acute infection). This suggests “tolerance” biologically between humans and this virus. The ZV can apparently fly below the radar screen of the immune system in some individuals. It is unknown how frequently this is the case since the natural history of ZV infection is still being worked out.
What this all means is that ZV should spread immediately as a “novel” virus (to most of our immune systems, as we’ve never before encountered it in the U.S.) through our human and mosquito population in the southern-most U.S. over the next few years. Once the population has been largely immunized by passage of the ZV through “the human herd”, the incidence of ZV infection and resulting complications to both adults and unborn children will decline substantially. The incidence of these problems will then vary according to the density or scarcity of total mosquito populations. For instance, if we entered a period of several years of relative drought, causing decline in mosquito numbers, then the percentage of humans growing up never having been infected would increase. Once drought conditions reversed, mosquito numbers would increase and there would be a substantial fraction of the general population that would be at risk– and so, there would be another outbreak of ZD. This is how contagious illnesses cycle according to ecological factors, disease vectors, and community-wide immunity (or declining immunity) to the infectious agent (ZV, in this case). Understanding these associations and the biology in this model of infection will be the best predictor of future events in the U.S.
But, it is now apparent that this Zika virus is a mutated form of the one that pre-exitsed over decades in other parts of the world. So, it would be “novel” to humans in terms of its biology and potential for complications and ill-effects heretofore not seen. That story is now only beginning to unfold.
- This summer, we will see ZD explode across our South. Next summer, possibly there will be spread northward.
- Public officials will emphasize mosquito control efforts, both by local government and individual homesteaders (see our other piece on this on the website).
- Very likely, there will be increasing numbers of microcephalic/neurologically damaged babies, especially among the poor with little access to reliable information and healthcare (lower socio economic groups have much more mosquito exposure).
- ZV will become permanently endemic in the U.S.
- Guillain-Barré (polyneuritis) syndrome will increase in association with ZD, though it will not be a prevalent issue, any more than it is in association with other preceding viral diseases, like influenza.
- Vaccine development will start in earnest. Why? Because there will be a huge market for it– young U.S. couples who want to have children will demand and pay for it. Third World diseases do not get capital directed at them until the West sees it as an existential threat to itself. Ebola vaccine development became a priority when exportation to the West was a reality.
- ZV science will evolve- its biology and the medically relevant issues. For instance, now it is known the ZV can be sexually transmitted. However, it is not known how long after the initial infection the ZV remains viable in semen and remains transmissible that way. ZV has also been found in urine and saliva, but it is unclear whether it can be transmitted that way. Chemical issues regarding saliva and urine may alter the virus so it cannot then effectively invade. Information on Ebola virus is still emerging from the last pandemic. Nine months after infection, the New York physician who was repatriated with Ebola disease was found to have viable Ebola virus in his eye fluids. So, ZV/ZD will be a work in progress for some time as our scientific community turns on it; revised ZD guidelines will continue to be announced over the next couple years (stay tuned as we post them).
- Be always aware that public officials may downplay the facts (knowledge is the antidote for panic), because part of their job is to maintain order. See my writing on the 1918 Spanish Flu Pandemic and how the highest level San Francisco government officials gave the public misinformation to maintain order- costing thousands of lives of an overly-pacified general population. This is not that situation, but you get the idea. (CDC officials similarly “laundered” their statements during the Ebola outbreak).
What Can you Do?
1.Stay on top of this, especially if you are sexually active and of childbearing age.
2.Until ZD becomes endemic in the U.S. (probably this summer), be attuned to your exposure risk in any country where it is endemic.
- Women to consider pregnancy test before and after such travel.
- Mosquito repellents on skin and clothing during and for 2 weeks after such travel (to prevent our local mosquitoes from picking it up from you if you are not ill but have the virus in your blood the last day of your trip and for an as yet undefined time after).
- Attention to mosquito bite prevention while traveling: air conditioning, airtight windows/screens, etc.
- Birth control and safe-sex methods the week before, during, and after travel in ZD areas.
- Refrain from birth conception for 6 months after ZD zone travel.
- If sexually intimate with someone in the past 6 months who had been in a ZD zone, get tested for ZV by an expert.
3. If actively attempting pregnancy during “mosquito season”,
- Keep clothing treated with permethrin.
- Maintain DEET-containing repellents applied to exposed skin.
- Once pregnant, both parents should be tested for ZV; if positive, consult with an expert on proper monitoring of the fetus’s development.
4. Stringently attend to mosquito control around property and neighborhood (see elsewhere on our website: “Mosquito Control”).
Periodically, we will update this information
Ed Rensimer, MD