What is Zika?
Zika is a virus, ostensibly the least harmful of the diseases transmitted by the female Aedes aegypti, or yellow fever, mosquito. Only one in five people infected via a mosquito bite will get sick. Generally the symptoms, which include rash, fever, joint pain and conjunctivitis, are relatively mild, so many people do not even realise they have been infected. As of yet there is no vaccine.
That doesn’t sound too bad. Why all the fuss?
Because Zika has been linked to a spike in the number of babies born in Brazil with microcephaly. This neurodevelopmental disorder causes new infants to have abnormally small heads, as the brain fails to grow normally. The condition is associated with developmental delay and mental impairment. More than 3,500 cases of previously rare microcephaly have been registered in Brazil in recent months in regions where Aedes aegypti thrives.
Is the link between Zika and microcephaly confirmed?
Microcephaly can be caused by a host of factors, but researchers believe that the sudden spike of cases in Brazil has been caused by mothers becoming infected with Zika while pregnant. Although yet to be proven definitively, the link between Zika and microcephaly has led governments in some affected countries to warn women to avoid getting pregnant, and for other nations to advise pregnant women against travelling to affected regions.
What if I am pregnant and have to travel to a Zika-affected region?
The advice is to take measures to avoid being bitten by mosquitoes. But, as anyone living in mosquito-blighted regions can tell you, this is a near-impossible task, no matter how vigilant one is.
What about women who are trying to get pregnant?
In such cases the advice becomes less clear, reflecting official uncertainty about the threat faced. The Zika virus usually remains in the blood of an infected person for only a few days, or perhaps up to a week. But it has been found in other body fluids after that; it is not fully understood what risk this poses. That has led some researchers to advise women who are trying to get pregnant to avoid travelling to affected regions.
So where are the affected regions?
Worryingly, more and more of the planet’s tropics. Zika was first identified in Uganda in 1947, and until 2007 confirmed cases were rare and confined to Africa and southeast Asia. But since then it has reached several Pacific islands. It was first detected in Brazil last year, since when it has spread to much of South and Central America and to the Caribbean. The World Health Organisation described its spread this week as “explosive”.
Where could it appear next?
In places that have not yet detected the presence of the Zika virus. The A edes aegypti mosquito is already established in the Indian subcontinent, Florida and other parts of the southeastern United States, and northeastern Australia, where it already transmits the sometimes fatal Dengue fever. Our increasingly interconnected world favours Zika's spread. A person infected with the virus can introduce the disease to a new region by being bitten by a member of an existing mosquito population that until then was unaffected by Zika. Some researchers believe the disease might have arrived in Brazil in this way with visitors attending the soccer World Cup, in 2014.
Does Zika pose a threat to Ireland?
Zika can spread only by mosquito bites, and A edes aegypti needs plenty of heat and rain to thrive. Ireland's cold climate acts as a sturdy defence against the disease. A Danish man who has tested positive for the virus after a trip to Mexico and Brazil is expected to recover soon, and his doctor says he sees no risk of the disease spreading farther in Denmark.
