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Public Health England has strengthened its advice on Zika, saying pregnant women should postpone non-essential travel to areas with disease outbreaks.

Previously it had encouraged expectant mothers to reconsider such travel because of the potential harm the virus might pose to babies in the womb.

If travel is unavoidable, they should take precautions to avoid bites from mosquitoes that spread the disease.

In recent months, Zika has been spreading across much of the Americas.

The infection has been linked to cases of microcephaly - babies born with underdeveloped brains.

In February, the World Health Organization declared the situation a global public health emergency requiring a united response.

Prof Paul Cosford from Public Health England said: "As our knowledge of the Zika virus, and the evidence linking microcephaly to Zika infection, becomes clearer a more precautionary approach is warranted. This advice will be kept under review and updated as more information becomes available.

"We expect to see small numbers of Zika virus infections in travellers returning to the UK, but the risk to the wider population is negligible as the mosquito vector is not found in the UK."

The symptoms of Zika infection may include:

fever

joint pain

rash

conjunctivitis/red eyes

headache

muscle pain

eye pain

A spokesman for ABTA, the travel association, said pregnant women due to travel to any of the destinations affected should seek medical advice from their GP.

"Where it is necessary to change or cancel their holiday arrangements in light of the NaTHNaC advice, they should request that their GP provides them with a medical certificate in order to assist them with any possible insurance claim.

"Travel companies will try and be as flexible as possible with pregnant customers who had already booked before the advice changed, and many are offering customers the option to amend their holiday to an alternative destination free of charge."

More on the Zika crisis:

What you need to know Key questions answered about the virus and its spread

Key unanswered questions The many things we do not know about Zika

The mosquito behind spread of virus What we know about the insect

Abortion dilemma Laws and practices in Catholic Latin America