So what is known today about this disease?

Zika is an arbovirus, which means a virus transmitted by a mosquito. It belongs to the flavivirus family that includes the dengue, chikungunya and Japanese Encephalitis viruses. Zika is not a new virus. It was first identified in the Zika forest in Uganda in 1947, hence the name, and was responsible for outbreaks in Micronesia in 2007 and in French Polynesia in 2013. Sexual contamination of the Zika virus has recently also been demonstrated in the USA but this route of transmission is likely to remain negligible in comparison with mosquito bites.

Right now, Zika outbreaks are mainly hitting Latin American countries and some West-Indies islands. However as the vector is the ubiquitous mosquito from the Aedes genus, there is a significant likelihood that the virus will spread too in other tropical countries in Asia (including theMekong countries), Africa as well as the southern parts of the western hemisphere due to the new expansion of Aedes in these latter regions. To date, only a few cases have been reported in Thailand over the last few years. Contrary to the Anopheles mosquitoes that transmit malaria, the Aedes mosquitoes are particularly well adapted to urban areas.

In about 80 per cent of the cases, a Zika infection is essentially a benign illness inducing no or mild symptoms. When symptoms do occur, the patient may present a skin rash, mild headache, low-grade fever, muscular and joint pains, fatigue and red eyes (conjunctivitis) for a few days. Some of these symptoms may be suggestive of other tropical diseases, in particular dengue.

The diagnosis is confirmed by specific tests to identify or isolate the virus in the blood.

The main issues with Zika infection are the suspected neurological complications that include the possible newborn defect named microcephaly -a congenital brain condition where a baby’s head is much smaller than average size – and the Guillain-Barre syndrome a progressive and potentially severe neurological disorder in adults that may be – although rarely – irreversible. Despite the 20-fold increase in microcephaly in some Brazilian states and the proven maternal-foetal transmission of Zika during pregnancy, the association of Zika with the birth defect complications is based on epidemiological data and not yet formally established. However, some public health authorities have already issued various recommendations for pregnant women. These include specific Zika screening and/or avoid travelling in endemic Zika areas and/or considering postponing planned pregnancy and/or strictly following advice to prevent mosquito bites.

There is no antiviral medication to treat Zika virus infection and no vaccine to prevent it. In symptomatic cases, the treatment is limited to relieving the intensity of fever and joint pains. Aspirin should be avoided due to the risk of haemorrhage induced by possible concomitant dengue infection.

The Guillain-Barre syndrome complication is treated with supportive care because there is also no cure for this disorder. However most patients eventually recover from this syndrome. On the other hand and depending on its severity, the microcephaly complication usually leads to lifelong developmental and neurological problems that can be life-threatening.

The basic prevention of Zika infection, like other arbovirus diseases, is then to avoid mosquitoes bites as much as possible. For children, leisure or playgrounds infested by insects should be avoided at anytime of the day. Long sleeved clothing should be worn. The use of repellent, preferably one containing DEET (N.N-diethyl-3-methylbenzamide), in regular applications every two to four hours, is recommended as well as the use of mosquito nets. Aerosol insecticide may occasionally be sprayed in the house.

Despite huge challenges, global prevention nevertheless starts from implementing serious public health measures to reduce standing water in the urban environment, which tends to lead to a significant reduction in the mosquito population.

DR GERARD LALANDE is managing director of CEO-Health, |which provides medical referrals for expatriates and customised |executive medical check-ups in Thailand. He can be contacted at gerard.lalande@ceo-health.com.