Zika virus

Zika virus

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Zika Virus is a mosquito-borne illness that is present in tropical areas. It frequently does not cause any symptoms, or if symptoms occur they are usually mild. It appeared in Brazil in May 2015, probably linked to an outbreak in French Polynesia, and since then has spread to at least 25 countries and territories in the Americas. Due to the widespread presence of the type of mosquito which can transmit Zika, the Pan American Health Organisation (PAHO) warns it will likely spread to all countries in the Americas except Canada and continental Chile(1 PAHO Statement on Zika Virus Transmission and Prevention, 2 February 2016 Pan American Health Organisation).

There now appears to be growing evidence linking the virus to birth defects, and neurological complications. As there is no specific treatment available, and no vaccine to prevent the disease, a number of authorities have advised pregnant women to “consider postponing travel to the areas where Zika virus transmission is ongoing”(2 Questions and Answers: Zika virus (Zika) and Pregnancy, United States Centers for Disease Control and Prevention, accessed 26 January 2016). Some health authorities have advised women living in Zika outbreak areas to delay falling pregnant.

The situation is rapidly evolving, and information is frequently changing or being updated. An increasing number of travellers are being diagnosed with Zika after returning from affected areas. International SOS is monitoring closely. For the latest updates log on to the Zika website or https://www.internationalsos.com/member-zone and view the medical alerts and country guides.


Zika virus is transmitted to people through the bite of Aedes mosquitoes. These are the same mosquitoes which can also transmit dengue and chikungunya viruses. Aedes mosquitoes live in urban areas and bite mostly during the day.

Zika virus can be passed from an infected pregnant mother to her baby. Spread through sexual contact (from men to women) is possible, although unusual. Transmission via blood transfusion has occurred. Monkey bites may potentially spread Zika too.

A lot more research is underway to determine if Zika can spread from person to person through other body fluids such as saliva, urine or breast milk. Nevertheless, the main way people are infected is through mosquito bites.


Most people have no symptoms. If symptoms do occur, they are usually mild – a fever, rash, muscle and joint pains, and red eyes (conjunctivitis), similar to many other viral illnesses including flu, dengue and chikungunya.
Abdominal pain and diarrhoea are seen less often. Lymph nodes may become enlarged.
Most people recover fully in about a week.

A rising number of reports of “Guillain–Barré syndrome” (GBS) associated with Zika infections are appearing from several countries. GBS is a muscular weakness which can be mild or severe, and in some cases can be fatal, particularly if the muscles of breathing are affected.

Brazil has documented an increase in cases of “microcephaly” (a severe birth defect in newborns manifesting as a small head circumference associated with developmental problems), coinciding with outbreaks of Zika. The Brazilian Ministry of Health determined that at least some of these babies tested positive for Zika virus, and many of their mothers recalled or were proven to have infection during pregnancy.

French Polynesia has reported an unexpected rise in the number of babies born with brain malformations, including microcephaly, which may also be linked to Zika infection in the first or second trimester of pregnancy.
While there is increasing evidence to support a link between Zika, microcephaly and other birth defects, investigations are ongoing to determine whether Zika infection alone is responsible.


A specific blood test is used to diagnose Zika virus. Testing is not widely available, and samples may need to be sent to certain reference laboratories.

As the disease is similar to, and occurs in areas where there is chikungunya and dengue (other mosquito borne diseases with similar symptoms), testing needs to be performed to confirm the exact diagnosis.


No specific treatment is available. Symptoms can be managed with bed rest, fluids and medications to reduce fever. Aspirin and non-steroidal anti-inflammatory medications (such as ibuprofen and naproxen) should be avoided unless dengue has been excluded (due to the increased risk of bleeding).


There is no vaccine against Zika virus. The main way to prevent infection is to prevent mosquito bites.
Use of condoms prevent sexual transmission.

Prevention is most important for pregnant women, and those who are trying to fall pregnant, due to the possible association with birth defects.

Risk to Travellers

Zika is present in tropical areas of the Americas, Africa, Southeast Asia and Pacific Islands. See the International SOS country guides and the Zika website for more detail.

A number of travellers have been diagnosed with the disease after returning to their home countries. Whilst some of these travellers had visited areas with known outbreaks, others had been to places where the disease is known to be present but no active outbreak was reported.

Travel Advice

If travelling to an affected area, prevent infection by preventing mosquito bites.

  • Use an effective insect repellent that contains DEET, Picaridin, PMD, or IR3535.
  • When outdoors, wear clothing that covers most of your body (long sleeves, long pants, socks and shoes).
  • Ensure windows are covered with fly-wire.
  • Consider using an insecticide-treated bed net.
  • Use “knock-down” insect spray to kill mosquitoes in your room.
  • Choose air conditioned accommodation if possible.

Prevent sexual transmission through using condoms.

Pregnant women contemplating international travel are advised to consult their doctor for an individual risk assessment and advice prior to any travel, regardless of destination. In addition to the infectious risks of any destination, it is important to consider the standard of available healthcare, and the availability of obstetric and neonatal specialist support (should it be required).

Note that some authorities, including the US CDC, are advising pregnant women (in any trimester) or those who plan to become pregnant to consider postponing travel to any area where Zika virus transmission is ongoing.

After Travel

Monitor your health for two weeks. If you develop symptoms, ensure that you see a doctor and advise them of your travel. Malaria is known to circulate in parts of some countries in the Americas and you may need to be tested and/or treated for malaria.

As Zika virus may persist in semen, men who have travelled to a Zika affected area authorities advise the use condoms for 28 days if their partner is not pregnant, or if their partner is pregnant – for the duration of the pregnancy.

If you are returning to an area that has Aedes mosquitoes, continue to prevent mosquito bites for 2 weeks (e.g. using insect repellent). This will reduce the risk of infecting local mosquitoes with Zika, and therefore reduce the risk of an outbreak.


International SOS Zika website
International SOS – Country Guides

Further Information

WHO Zika virus information http://www.who.int/csr/disease/zika/en/
CDC Zika virus information http://www.cdc.gov/zika/


This information has been developed for educational purposes only. It is not a substitute for professional medical advice. Should you have questions or concerns about any topic described here, please consult your healthcare professional.

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