People with chronic illnesses and those with immune system disorders are being urged to seek advice from a health worker before travelling to countries affected by the Zika virus outbreak.
Travel health experts had originally just advised pregnant women to reconsider travel plans to affected countries.
But now the National Travel Health Network and Centre is urging others to also seek advice before travelling to one of the affected countries.
The Foreign Office urges people to heed the advice of the Centre.
"Before you travel, you may wish to seek advice about ongoing outbreaks from a health professional," the advice states.
"This is particularly relevant if you are pregnant, suffer from a severe, chronic medical condition, or have a medical condition that weakens your immune system."
There is an unprecedented outbreak of the virus in Brazil and the World Health Organisation said that the virus is likely to spread across nearly all of the Americas apart from Canada and Chile.
The virus - which causes symptoms including rash, fever, conjunctivitis and headache - has been linked to birth defects in children born to mothers infected while they are pregnant.
Around 4,000 babies born to mothers infected with the Zika virus in Brazil have been born with microcephaly - a condition where the child has an underdeveloped brain.
The virus has already been found in 21 countries: Barbados, Bolivia, Brazil, Colombia, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname and Venezuela.
There is no treatment or vaccine and many South American countries have called on women to consider the implications of the infection before getting pregnant.