Cuba has confirmed the deaths of 33 people from mosquito-borne illnesses in recent months in an epidemic that has hit at least one-third of the population.

Deputy Minister of Health Carilda Peña said 12 people had died of dengue and 21 of chikungunya, the two viruses circulating widely across the Caribbean island nation.

At least 21 of those who died were under the age of 18, Peña said.

The minister did not specify a date range for the deaths.

The deaths, and still-raging epidemic, are more bad news for Cuba, whose healthcare system is already facing existential struggles due to a gruelling economic crisis that has prompted widespread shortages of food, fuel and medicine.

Dengue fever has long plagued Cuba, but has grown worse as a shortage of funds and fuel hampers the government's ability to fumigate, clean roadside garbage and patch leaky pipes. Chikungunya, once rare on the island, has also spread quickly in recent months.

There is no specific treatment for chikungunya, which is spread primarily by the Aedes mosquito species, also a carrier of dengue and Zika.

Chikungunya causes severe headache, rashes and joint pain that can linger months after infection, causing long-term disability, though it is rarely fatal.

Havana and Santiago, Cuba's two largest cities, have seen some of the highest rates of infection in recent weeks.

Peña reported 5717 new cases of chikungunya in the last week, though officials say many cases go undetected because most patients do not see a doctor or report that they are ill.

The World Health Organization in July issued an urgent call for action to prevent a repeat of an epidemic of the chikungunya virus that swept the globe two decades ago, as new outbreaks linked to the Indian Ocean region spread to Europe and the Americas.