British couples have been advised to stop trying for a baby for up to six months if a partner has returned from one of 23 countries affected by the Zika virus.

Public Health England (PHE) said all men should use condoms for 28 days after coming home from countries like Brazil and Mexico if their partner was at risk of pregnancy, or already pregnant.

Men who had suffered an unexplained fever while travelling, or who had been diagnosed with the virus, should avoid unprotected sex, or trying for a child for six months. Women have already been advised to avoid travelling to infected countries if they might be pregnant or are trying for a child.

Around half a million people are believed to have travelled to Zika-infected countries in the last six months, according to the most recent figures from the Office for National Statistics.

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The virus has already caused nearly 4,000 cases of malformed babies in the Americas and the World Health Organisation warned yesterday that the disease was spreading so quickly that four million people could be infected by the end of the year.

Although the disease is mainly transmitted through mosquitoes, PHE said sexual transmission had been recorded in a "limited number of cases".

Public Health England advised: "If a female partner is at risk of getting pregnant, or is already pregnant, condom use is advised for a male traveller for 28 days after his return from a Zika transmission area if he had no symptoms of unexplained fever and rash.