Virologists have been expressing concern about Zika virus for a couple of years now, but it’s only with its arrival in Puerto Rico during the holiday season that it has really started to make the news.

Some of the headlines have focused on the apparent association between Zika infection in pregnant women and the birth of babies with small brains – a condition known as microcephaly. This association is still largely circumstantial, but if true would be extremely alarming. Zika has also apparently changed its behaviour in other ways, spreading faster, spreading sexually, and also lumbering some survivors with the nasty post-viral Guillain-Barré Syndrome. Although GBS can be fatal, the worst GBS manifestation in recovered Zika patients so far has been a partial temporary paralysis.