A study published in a U.S. medical journal says mosquito-borne dengue disease costs Puerto Rico nearly $40 million a year for treatment, surveillance and other expenditures.

A team of researchers from Brandeis University says households in the U.S. territory pay almost half of that cost, with the government and insurance companies splitting the rest.

Puerto Rico had its largest ever dengue outbreak in 2010 with more than 12,000 suspected cases and a record 31 deaths. At least 77 cases have been reported so far this year, above the historic average.

The study was published Wednesday in the American Journal of Tropical Medicine and Hygiene. It was funded through a contract with vaccine maker Sanofi Pasteur.