What are its effects?
Until last year Zika was thought to cause only a minor illness, with up to 80 per cent of individuals experiencing no symptoms. People with symptoms usually suffer from a fever lasting four to seven days, possibly accompanied by a rash, conjunctivitis, muscle and joint pain, and headache, commencing two to seven days following exposure.
However, during large outbreaks in French Polynesia and Brazil in 2013 and 2015 respectively, national health authorities reported potential neurological and auto-immune complications, including an increase in birth defects. There is now a scientific consensus that Zika is a cause of microcephaly, an abormal smallness of the head associated with incomplete brain development and potentially lethal at birth, and other congenital anomalies as well as Guillain Barré syndrome, "a rare and serious condition of the peripheral nervous system", according to the NHS.
Guillain Barré syndrome (also known as GBS) is believed to be triggered by an immune reaction. Nerve damage can lead to muscle weakness, paralysis and other neurological symptoms.
The Foreign Office says, however, that "serious complications and deaths from Zika are not common".