There has been a lot in the press recently about zika virus. Public Health England has now advised that pregnant women should postpone non-essential travel to areas with disease outbreaks.
Zika virus was first identified in monkeys in Uganda in 1947 and the first human case was detected in Nigeria in 1954.
There have been small outbreaks, but zika was not thought to be a major human threat until May 2015.
It started spreading rapidly in Brazil and has now spread through much of northern South America and Mexico.
Many infected people do not get symptoms, and for those who do they are often mild, flu-like symptoms.
The concern is the effect the virus has on unborn babies. The infection has been linked to microcephaly – when the baby is born with an abnormally small head, because the brain has not developed correctly. Some babies do not survive, and those who do may have severe learning disabilities and delay in development.
The virus is spread by mosquitoes that transmit infected blood from one person to another.
It is thought, at the moment, that an infected person has active virus in the blood for about a week. There have been some cases of the virus being transmitted sexually to people who have not visited affected countries, but this seems very rare.
Some countries are advising men returning home to use condoms if their partner is pregnant. At the moment the advice is condoms for a month if the man has no symptoms and six months if he does.
Zika virus has also been found in other bodily fluids including saliva and urine, but it is unknown whether the virus can spread through these routes.
As there is no treatment, the advice when travelling is to try and avoid being bitten. So using insect repellents, wearing long-sleeved clothes and keeping doors and windows closed is advised.
The US Centres for Disease Control says zika lingers in the blood for about a week and advises that babies conceived after the virus has cleared will not be affected. At the moment there is no evidence that infection poses a risk to future pregnancies.
It is likely that information and advice will change, but the main advice is for pregnant women not to travel to at risk areas, and to follow the guidelines issued.
As with so many health scares, it is a balance between being wise but not paranoid.