The weather phenomenon known as El Nino could lead to an epidemic of dengue fever cases in southeast Asia, international researchers say.
Cases of dengue fever have been shown to rise along with the ocean warming trend, which occurs some years but not others. The current El Nino, which has already begun and is forecast to last into next year, is expected to be among the most intense in 20 years, researchers say.
"Large dengue epidemics occur unexpectedly, which can overburden the health care systems," said lead author Willem van Panhuis, assistant professor of epidemiology at University of Pittsburgh Graduate School of Public Health.
"Our analysis shows that elevated temperatures can create the ideal circumstance for large-scale dengue epidemics to spread across a wide region."
Researchers analysed 18 years of monthly dengue surveillance reports across Southeast Asia, according to the study published in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal.
They found trends among the total of 3.5 million reported cases in eight countries.
During the last particularly strong El Nino season, in 1997 and 1998, "dengue transmission was very high, matching up perfectly with high temperatures that allowed mosquitoes to reproduce faster and spread dengue virus more efficiently", said the study Monday.
The higher temperatures in the tropics and subtropics were brought on by El Nino, moving warm sea water temperatures in the eastern Pacific toward the west.
Dengue fever is caused by a mosquito-borne virus in the tropics and subtropics, causing nearly 400 million infections each year.
Symptoms can include fever, severe pain, headache, nausea, vomiting and skin rashes. In some patients, the infection can be fatal.
There is no vaccine to prevent dengue and no medical treatment other than acetaminophen.
The World Health Organisation says the global incidence of dengue has grown dramatically in recent decades, and about half of the world's population is now at risk.