Health officials say that dengue cases this year are more than 30,000, and these are only the cases that have somehow been involved with the public health system. So the total may be much higher.
That represents a 280 percent increase over the same period last year, according to the Refindora Costarricenes de Petróleo, S.A., which has an anti-dengue program.
Although there are indications that the number of cases is declining, there still are about 1,500 new ones reported each week.
The epidemic has had an impact, so far unmeasured, on Costa Rica tourism. Much of Central America also is facing similar conditions brought about by the Aedes aegypti mosquito, which spreads the viruses.
Although there has been a surge in cases in the Central Valley, the numbers are nowhere near those of the coastal communities.
The Refinadora Costarricense said Tuesday that its facilities have been sprayed regularly this year. The largest facility is in Moín, Limón, which is a center of dengue infection. Mosquitoes also carry malaria, which still affects some Caribbean residents.
The refinery also has been involved in campaigns to promote cleanups. Eliminating the receptacles of stagnant water where the mosquitoes breed has been the most effective approach. Refinery workers are carrying the message to residents in the Limón area.
Dengue, also called bone breaker disease, varies with the individual. One bout can provide immunity, but there are at least three forms of the virus in Costa Rica now. A second infection can be life-threatening. At least 70 persons have suffered the most serious form this year, and there have been deaths.
Potential tourists have been worried because dengue is most prevalent in coastal areas that are vacation centers. The various commercial mosquito repellents are highly effective and can provide tourists with protection.