Resident of Yolo County Tests Positive for Zika Virus – First, Don’t Panic

ZikaBy Tia Will

As reported in the L A Times 2/11/16:

“The person, whose identity and gender were not released, had recently traveled to a country in the Caribbean or Central or South America and contracted the virus, said Beth Gabor, a spokeswoman for the Northern California county. The individual is not pregnant and has mild symptoms.”

So what should you do? My preliminary recommendations as a healthcare provider at this time are as follows:

  1. Any woman who is pregnant or capable of becoming pregnant should avoid travel to any of the countries currently experiencing Zika outbreaks. Lists of countries are readily available on line. If in doubt, check with your health care provider prior to making travel plans.
  1. Since the mosquito born virus has been spreading rapidly in the western hemisphere, I recommend that we all take the usual precautions with regard to mosquito abatement. Avoid standing pools or bowls of water on your property. Report them to the city if on public property. As we move into the warmer months, I recommend prudent use of individual anti-mosquito products when outdoors and use of protective clothing.
  1. Check online “Fight the Bite” information. Although the affected species of mosquito do not appear to be here yet, it is not unrealistic to think that they will be.

From County Press Release:

The Centers for Disease Control and Prevention (CDC) confirmed today that a Yolo County resident has tested positive for Zika virus. This individual recently traveled out of the country and had a mild case of Zika.

Zika virus is a relatively new disease for the Western hemisphere. It first appeared in Brazil in May of 2015. It has since spread to 20 countries in Central and South America and the Caribbean, including Mexico. Zika is spread through mosquito bites, not casual person-to-person contact. According to the CDC, the most common symptoms are fever, rash, joint pain and red, itchy eyes. Symptoms are usually mild and last several days to a week. Many people who have Zika will not experience symptoms. There is currently no vaccine or treatment for Zika.

Pregnant women, however, are believed to be most at risk for complications from the Zika virus because serious birth defects have been reported in infants born to women infected with the virus. The CDC is planning studies to learn more about the connection between Zika and children born with these birth defects. In the meantime, the CDC has issued travel guidance for women who are pregnant or who may become pregnant. To stay up-to-date on the CDC’s latest travel notices, visit:

“Yolo County residents traveling to Central or South America or the Caribbean, where Zika is present, should take precautions against mosquitoes,” said Yolo County Health Officer Ron Chapman, MD, MPH. “If you are pregnant, consider postponing your trip. All travelers to areas where Zika is present should go to their doctor if they experience any of the symptoms associated with Zika within three to seven days after they return. Pregnant women who have recently traveled to an area with Zika should talk to a healthcare provider about their travel even if they don’t feel sick.”

Ways to avoid mosquito bites include:

  • Using an insect repellant containing DEET, picaridin, IR3535 or oil of lemon eucalyptus;
  • Wearing long-sleeved shirts and trousers;
  • Using air conditioning or window and door screens to keep mosquitoes outside; and
  • Reducing the number of mosquitoes inside and outside your home by emptying standing water from containers such as flowerpots or buckets. Mosquitoes can breed in as little amount of water as a bottle cap.

To learn more about Zika virus, visit: and

About The Author

David Greenwald is the founder, editor, and executive director of the Davis Vanguard. He founded the Vanguard in 2006. David Greenwald moved to Davis in 1996 to attend Graduate School at UC Davis in Political Science. He lives in South Davis with his wife Cecilia Escamilla Greenwald and three children.

Related posts


  1. tribeUSA

    Dr. Tia–Is it known if the Zika virus is in a class of viruses that, after the initial infection and possible symptoms, remain dormant at low-levels in the body, and then perhaps flare-up again months or many years later (e.g. like some herpes virus strains, both sexual and non-sexually transmitted).

    With regard to women and pregnancy, concerns would include asymptomatic infections–where you harbor the virus but don’t exhibit symptoms and likely do not know you are infected. Or, a womans sexual partner is infected but does not know it, and unwittingly passes the virus to the woman shortly before conception, or during conception and pregnancy. Can a woman be an asymptomatic carrier during pregnancy, but nevertheless infect the fetus and the risk of a deformed/disabled baby?

    As I understand it, most infected people do not exhibit marked symptoms, but can nontheless can transfer the disease (via sex or mosquito or blood transfusion) to other people.

    Are mosquitos in Yolo being tested for Zika?

    Seems to me this is a potentially very serious situation, particularly if/when Yolo mosquitos start to become carriers, and if the virus can be long-term latent/asymptomatic and/or persists (e.g. after symptoms abate) at low levels for long periods in many human carriers, and yet nevertheless be transmitted by mosquitos, sex, and blood transfusions (another screening test for the blood banks, in addition to the myriad other things that need to be screened).

  2. tribeUSA

    Dr. Will–along the lines of my above post; if I was a woman considering having a child (or her husband), I’d be concerned about being an asmptomatic carrier and yet risk infecting the fetus–I would also want to know if, after infection with Zika (symptomatic or asymptomatic), the virus tends to clear nearly completely out of the body within a few months and is reduced to very low (noninfective) levels; or alternatively if, like the herpes virus, it can remain dormant in the body for years and flare up unexpectedly years later–so that the woman is forever-after at significantly increased risk of an infected fetus if she wants to become pregnant? (the nightmare scenario; let’s hope this is not the case!)

  3. Robb Davis

    tribeUSA – The CDC states this about sexual transmission of Zika.  Of note:

    …the duration of persistence of Zika virus in semen remains unknown… As we learn more about the incidence and duration of seminal shedding from infected men and the utility and availability of testing in this context, recommendations to prevent sexual transmission of Zika virus will be updated.

    Also from the link in this article please note the following:

    The mosquito carrying Zika is aedus egypti (it is also carried by aides albopictus). This is the same mosquito that is a vector for yellow fever (for which there is a vaccine) and, more importantly in my view, dengue fever, for which there is not a vaccine.  These mosquitos have not been detected in Yolo or surrounding counties but have been found further south.  Milder winters may lead to their spread northward.  These mosquitos, unlike the vector for West Nile, are more likely to bite during the day and also more likely to lay eggs in small water sources around homes and in urban areas.

    At this point I am more concerned about dengue than Zika because it is very debilitating.  I would argue that we need more robust community-based vector control programs (in addition to vector control district actions) that would require much more vigilance by all citizens.

    1. Robb Davis

      I agree.  We need to close the internal borders to Hawaii since they already have dengue there.

      Second US Citizens should be allowed to leave the US to go to malaria or dengue zones but they should NOT be allowed back in.  Or, we should hold them in quarantine until they show no evidence of having the parasites or viruses in their blood stream.

      A cleaner idea would be to simply close the border to aedus egypti and anopheles mosquitos.  Or, we could rule falciparum and dengue persona non grata…

  4. The Pugilist


    Three questions:

    1.  Does Zika pose risk to people who aren’t pregnant?

    2.  Has it definitively been linked to birth defects?

    3.  The other day I got into my car and when I got to work, I noticed many mosquitoes.  I don’t see how we can prevent mosquito bits unless we cut into the mosquito population.

    1. Tia Will

      Some very good questions coming in. Unfortunately my research capacity is severely limited at present. I will answer with what I know and hope to be able to write an article on this when able.

      For starters, good general articles addressing some of your questions, you might try :

      For my quick and dirty take on your other questions:

      1.”Is it known if the Zika virus is in a class of viruses that, after the initial infection and possible symptoms, remain dormant at low-levels in the body, and then perhaps flare-up again months or many years later ” 

      Not to the best of my current knowledge which is unfortunately very little at this time.

      2. “Can a woman be an asymptomatic carrier during pregnancy, but nevertheless infect the fetus and the risk of a deformed/disabled baby?”

      It would appear that this is a definite possibility given that many people who contract Zika are asymptomatic. Also we do not know how long the virus can be vertically transmitted once the mother has been infected, so even if there are not recurrent activations as is true with herpes, we still do not know when it is safe for a previously infected woman to attempt pregnancy.

      One thing important to remember is that we do not have definitive proof of causation. There is increasing evidence based on the concurrent increase in numbers of cases of Zika, and increasing numbers of microcephalic infants in Brazil. There is mounting evidence now with four cases of which I am currently aware of the Zika virus having been found in four specimens. Two specimens were found in the placental tissue from first trimenster miscarriages. Two were found in brain tissue from autopsies from third trimester ( near term) infants who died spontaneously shortly after birth who were also diagnosed with microcephaly.

    1. Robb Davis

      What I wrote above:

      These mosquitos have not been detected in Yolo or surrounding counties but have been found further south.  Milder winters may lead to their spread northward.  

  5. Tia Will

    Another reason for stronger border protection.”

    To keep people from traveling to other countries?”

    My thought as well.”

    At most an advisory, not a travel ban in either direction. A ban would be completely non productive unless you are postulating that someone plans on smuggling infected mosquitos across the border ! Not even Trump has latched onto that idea.

    My guess is that some missed the second part of my own chosen title – “First, Don’t Panic” . How many  millions of dollars wasted that could have been used for prevention, diagnosis and treatment of real and present illnesses were thrown away during the Ebola scare when there was not a single case in California and only a few people ( under 25 if memory serves me) qualified for monitoring.   I wanted to give a prudent heads up on this issue, not invite a political discussion about optimal border control for either two footed or winged creatures.


      1. wdf1

        Everything I have followed so far concerning zika and microcephaly says that a link is possible but not certain, and then there is the correlation vs. causation issue.  If you know of reliable sources that say otherwise, please share.  Otherwise the best way to improve certainty is to eliminate other possible causes.  Mosquito insecticide is a worthwhile cause to disprove in light of the damaging side effects (including birth defects) of DDT in the past.

        I’m okay with this source posing a plausible hypothesis that hasn’t yet been dis-proven.  If it has been dis-proven, please share.

  6. Tia Will


    With regard to the possibility of a pesticide as a casual factor in microcephaly, I believe the evidence to be at best very weak at this point in time. While it is true that chemical poisoning ( in the form of fetal alcohol syndrome) is known to be a cause of microcephaly and other neurologic problems, the same has not been definitively demonstrated for pesticides to the best of my knowledge although there has been much speculation about this possibility for many years, especially amongst farm workers.

    The second indirect bit of evidence favoring ( although not proving) viral infection as a cause is the fact that the rubella virus is known to cause severe neurologic damage in fetuses, thus demonstrating the ability of viruses to have this effect.

    Indirect evidence at best, but with the evidence presently available, I consider the chemical cause to be less supported at this point in time.

    1. wdf1

      Thanks for your insights. There also are an additional 3-4 links circulating on social media in the past couple of days that suggest a pesticide/larvicide link with microcephaly.

      1. wdf1

        Feb. 6, 2016, USA Today (other news venues have carried this story): More than 3,100 pregnant women infected with Zika in Colombia

        An analysis of Zika cases found a 66% increase of Guillain-Barre, a rare nerve disorder linked to the virus, but none of microcephaly, a defect in which babies are born with abnormally small skulls, Santos said. Health officials said three people in the country died from Guillain-Barre after contracting Zika.

        Boldface added.  This phenomenon will have to be resolved.  I guess this will be a morbid test.

Leave a Reply

X Close

Newsletter Sign-Up

X Close

Monthly Subscriber Sign-Up

Enter the maximum amount you want to pay each month
Sign up for