Zika

Zika is a viral vector-borne disease transmitted from animals and humans to humans. Only humans and non-human primates are known to be affected by the virus.

Contrary to common belief, it is not a new disease. Zika was first identified in the Zika Forest, Uganda in the 1940’s. A very large outbreak of Zika disease in 2015 in Brazil raised international concerns. The World Health Organization (WHO) declared a Public Health Emergency in 2016.

More than 80 countries have now reported Zika infection. Sporadic outbreaks had been noted in Asia between 2008 and 2015.

The Zika virus is mostly transmitted by the bite of a female Aedes mosquito. This is the same species responsible for transmission of both dengue fever and chikungunya. These mosquitos mostly bite during the day but can also bite at night. Their habitat relates strongly to urbanization with eggs being laid in small vessels containing water: bowls, buckets, dishes, and vases found inside and outside dwellings. Water in canoes and small ponds also provides good breeding sites. 

While most infected people have few, if any symptoms, there can be serious complications with infections prior to or during pregnancy. Zika can also be transmitted by sex from an infected partner. The partner may have been exposed overseas and be asymptomatic on return.

In a study of pregnant women with Zika infection, 5% resulted in birth defects. Approximately 1% of all Zika infections are likely to be sexually transmitted.

There isn’t a vaccine currently available.

Zika disease is a concern for travellers. Aedes mosquitos are found in many tropical and subtropical locations world-wide. Many countries have reported cases in popular tourist destinations.

A comprehensive list of these countries can be found at CDC.

CDC defines risk according to a number of variables:

• Current outbreak
• Past reports of Zika disease
• Low level risk based on altitude (> 2000m)
• Country or location with no previous reports
• Country or location with no mosquitos that transmit Zika.

Travel risk is mostly focussed on whether the individual is pregnant, intending to be pregnant or having a partner who is pregnant. Those in these categories must decide on whether they still want to take the risk and travel to a zika endemic area. A babymoon may not be sensible in a zika prone location like Bali, Phuket or the Pacific. Wait until at least 3 months after return before becoming pregnant.

A global overview of risk was published by the WHO in 2022.