The World Health Organisation (WHO) says the Zika virus is "spreading explosively" and looks set to declare the outbreak a "public health emergency of international concern" (PHEIC). What does this mean and how much do we know about the latest microbe to threaten global health?
What is a PHEIC? Defined as “an extraordinary event which is to constitute a public health risk to other states through the international spread of disease and to potentially require a coordinated international response”, it is essentially a call to arms to countries to galvanise resources in an effort to stop the further spread of the disease.
Can you tell me more about the Zika virus? A mosquito-transmitted infection originally discovered in the Zika forest in Uganda in 1947, the virus is common in Africa and Asia. It is related to dengue fever and the West Nile virus, both of which have spread globally in recent years. Zika is primarily spread by bites from the Aedes aegypti mosquito, after which the virus enters the blood stream.
Is it a serious illness? For most of the four million people who could be affected by the outbreak this year, according to the World Health Organisation, the Zika virus will cause a mild illness. Some 60-80 per cent of Zika infections are asymptomatic; for the remainder, the most common symptoms are fever with muscle ache, a rash, and red eyes. There is no cure for Zika fever, but those infected do not usually have to be hospitalised.
So why all the fuss? Since the Zika microbe was first identified in Brazil, in May 2015, it has spread rapidly in South and Central America. Its effect on pregnant women is a particular source of concern.
In the past year, a 3,800 per cent increase in unusually small heads (microcephaly) in the newborn children of mothers infected with Zika suggests at least an association between microcephaly and Zika infection during pregnancy. A percentage of children born with microcephaly will experience developmental delay and other signs of brain damage.
However, it may be that other factors, such as simultaneous infection with other viruses, are contributing to the rise. Scientists may even find that Zika virus is not the main cause.
There has also been a spike in cases of Guillain-Barré syndrome in affected areas. The syndrome occurs when viruses attack the nervous system, causing temporary paralysis of the lower limbs as well as the chest muscles required for breathing. Anecdotal reports of Zika virus transmission via blood transfusion and semen have triggered more detailed research into additional routes of transmission.
Should pregnant women travel to affected areas? No. A travel advisory from the Department of Foreign Affairs and Trade urges caution and the postponement of any travel plans to 20 countries in the Americas and the Caribbean by “pregnant women and women who are trying to become pregnant”. Some experts are advising caution on all women of childbearing age, to reflect the fact that one half of all pregnancies are unintended. They advise that “strict” birth control be practised when travelling in the affected regions.
Will there be a vaccine to counteract Zika virus? There is currently no vaccine available. Research on making one is under way, but it could take years for successful testing to be completed. Making vaccines from scratch can be an expensive business.
If I am travelling in Zika endemic areas, how can I protect myself? Stay in screened or air-conditioned rooms. Although the virus-laden mosquito tends to bite during the day, it would be prudent to sleep under a mosquito net. Try to wear insect repellent at all times and wear long trousers, long sleeves and a hat.
