Thailand Zika Travel and Pregnant?

Let's start with the bad news ...

Zika has been found in SE Asia since the 1960s (the disease was first identified in the late 50s) but only recently has become the darling pandemic of the news media.

Cases of Zika caused Microcephaly have been reported in Thailand in recent months.

Clusters of Zika infections have been recorded in parts of Thailand in recent months.

Let's add in a dose of reality in the tropics ...

Zika is just one of several nasty tropical diseases that are endemic to SE Asia, including Dengue, Japanese Encephalitis, Malaria. All are mosquito borne, but via different species of mosquitoes.

Let's allow some light through the dark clouds ....

Viruses like Dengue and Zika are live transmissions, the mosquito females bite an infected person then transmit the disease to the next person they bite. This causes outbreaks to be localized, as the mosquitoes can not carry the infected blood very far (they don't fly worth beans with a partially full belly).

Using mosquito repellent to avoid being bitten, eliminates a substantial portion of risk in contracting any of the diseases I mentioned. But keep in mind that the Aedes species of mosquitoes (the ones transferring Dengue and Zika) are day biters, so you need to use repellent anytime you plan to be sitting outdoors. And just because your hotel has no mosquito harboring plants or pools, you never know what is in the neighbors yard next door, so use it even sitting around outside at your hotel.

December is dry season for most of Thailand, so the mosquito population is diminished, but not totally gone.

The number of Zika cases reported versus the population of Thailand is minuscule.

Effects on your unborn child ...

Ultimately, you and your doctor (or a tropical medical specialist) should discuss the potential effects of Zika on your unborn child at various stages of its development. We are not medical specialists here on this website.

The US Centers for Disease Control and Prevention has comprehensive coverage of the Zika virus, including destination-specific information.

It has an section devoted to pregnancy in which it notes:

What we know

• Zika virus can be passed from a pregnant woman to her fetus.
• Infection during pregnancy can cause certain birth defects
• Zika primarily spreads through infected mosquitoes. You can also get Zika through sex.
• There is no vaccine to prevent or medicine to treat Zika.

What we do not know

• If there’s a safe time during your pregnancy to travel to an area with Zika.
• How likely it is that Zika infection will affect your pregnancy.
• If your baby will have birth defects if you are infected while pregnant.

The UK Travel Health Pro has the following alert for Thailand:

Zika virus in Thailand
This country is considered to have a high risk of ZIKV transmission. Increasing or widespread transmission has been reported. Pregnant women are advised to postpone non-essential travel until after pregnancy. Details of specific affected areas within this country are not available.

Prevention

• All travellers should avoid mosquito bites particularly between dawn and dusk.
• There is no vaccination or medication to prevent ZIKV infection.
• It is recommended that pregnant women planning to travel to areas with a high risk of ZIKV transmission should postpone non-essential travel until after pregnancy.
• Women should avoid becoming pregnant while travelling in, and for 8 weeks after leaving an area with active ZIKV transmission.
• If a woman develops symptoms compatible with ZIKV infection, it is recommended she avoids becoming pregnant for a further 8 weeks following recovery.
• Pregnant women who visited this country while pregnant, or who become pregnant within 8 weeks of leaving this country, should contact their GP, obstetrician or midwife for further advice, even if they have not been unwell.

I think we are beginning to build up a case that suggests Thailand may be no greater risk than many other countries pregnant women are visiting.

1] The reported cases in Thailand in the first 9 months of 2016 are 349 (assuming since January includes January.)

2] The Thai population is over 68M

3] The level of non-reporting is not known

4] Foetuses are more susceptible closer to conception than later (my assumption, see Figure 3). However experts don't know whether you're at higher risk if you get infected during a particular trimester.

5] A model using data from a Zika outbreak in French Polynesia estimated the risk of microcephaly in children born to mothers who acquired Zika virus in the first trimester to be 1%

6] With 4], later in pregnancy might be safer than indicated by 5]. However microcephaly is not the only birth defect to consider, though it seems the others are generally less severe (eg impairment of hearing and/or vision) though sometimes more severe (eg fatal).

7] On the other hand most babies born to pregnant women who get Zika appear to be healthy

8] The model may not be accurate or may not otherwise apply to Thailand. Experts don't know how likely your baby is to have birth defects if you get Zika during pregnancy.

9] CDC do not at present have a watch, alert or warning for Thailand

10] Travel Health Pro has:

This country is considered to have a high risk of ZIKV transmission. Increasing or widespread transmission has been reported. Pregnant women are advised to postpone non-essential travel until after pregnancy. Details of specific affected areas within this country are not available.

Judging by other usage of "non-essential travel" in health and safety warnings, coupled with no emboldening and no "very strongly" or "strongly" in front of "advised", this is barely more than a routine caution - almost obligatory from such a body and more akin to telling a child to be careful when crossing the road, rather than not to stick metal objects into power sockets.

CDC's wording is an even milder consider postponing:

women who are pregnant or planning to become pregnant should discuss their travel plans with their doctor and consider postponing nonessential travel to Thailand.

11] A combination of the above would suggest to me odds of around 1 in 100M per annum and better than that with proper precautions (DEET, no perfume, covering up at dusk and dawn avoiding areas of standing water, trying to stay indoors and high up, nets etc). Much longer than the chances of winning the lottery.

12] You will presumably be in Thailand for weeks rather than long-term, hence limit your exposure

13] If Aedes aegypti breeds like the malarial mosquito (malaria risk in Thailand estimated at 1:50,000) the rainy season is the time of highest risk, and that for Thailand usually ends in November, so you would be there after that.

HOWEVER, you must at least listen to what your doctor says as your medical history is relevant (eg will this add to a stress issue).

To take your questions in turn:

When during pregnancy will Zika cause harm to baby?

There is risk throughout pregnancy (see Comment below).

Do 100% of all bites lead to Zika?

Definitely not (eg there are other mosquitoes and insects that bite).

Is it likely we have a immunity?

My guess is no, but it does effect some people more than others. Once you've been infected with Zika, you're likely to have immunity from the virus but if so, how long for is not known.

are not all mosquitos carriers?

Not all mosquitoes are carriers. Not only does it depend on their species but also their gender.

See also: Is there a good and objective resource online about Zika virus?

and

How to avoid the contact with the mosquito that carries Zika Virus in Tropical countries

You have at least one full month untill December. Try to sell your trip so you don't lose (all) the money, and go on the trip when you are in better position. Ultimately it's up to you to take or not take the risk, but I hope you agree that it's better to stay on the safe side, especially when you can lose much more than you can gain.