British holidaymakers heading to the Caribbean have been warned about the spread of a virus that causes fever, rashes and severe joint pain.

The chikungunya virus, which is caught through bites by infected mosquitoes, has been spreading in the area since late last year, infecting 500,000 people so far, and experts say it is “just getting going”.

There have been at least 37 cases diagnosed in travellers returning from countries including St Lucia, the Dominican Republic, and Antigua and Barbuda.

The virus has spread to 25 Caribbean nations since it was first reported by the World Health Organisation, according to weekend reports.

Laith Yakob, a specialist at the London School of Hygiene and Tropical Medicine, told The Times that it was particularly serious in elderly patients and can be fatal.

The joint pain caused by the virus can be “very debilitating”, the WHO said, and in some cases persists for several months or longer.

Anyone travelling to the Caribbean should speak to their GP or a travel doctor before their trip and regularly apply insect repellent once in the region.

containing DEET and reapply every two hours, warning against sunscreens combined with insect repellents as they had not yet “proven efficacy”.

He added: “The importance of using a repellent is because both species of mosquitoes that spread chikungunya virus are day biters, so bed nets will not protect you from them.”

The countries hit hardest include the Dominican Republic, Haiti, Guadeloupe and Martinique. The disease has also spread to mainland South America and there have been a handful of cases reported in the US.

There is no vaccine or cure available for chikungunya but most patients recover well if their symptoms are treated.

Jane Jones, travel and migrant health expert at Public Health England, said: “Chikungunya is an unpleasant viral illness that is transmitted by day-biting mosquitoes. As there is no specific preventive medicine or vaccination against chikungunya, prevention relies on travellers avoiding mosquito bites — particularly around dusk and dawn when the mosquitoes are most active.”