4 dengue strains blamed for Digos outbreak

DIGOS CITY, Philipines  – Health authorities have blamed the circulation of four strains of dengue for the outbreak of the mosquito-borne disease that downed a total of 636 residents here in June and July.

City health officer Milagros Sunga said they discovered that all the four “zero types” of dengue have circulated here based on the blood samples collected from 57 patients.

Sunga said the blood specimens were analyzed at the Department of Health (DOH)-run Research Institute for Tropical Medicine in Muntinlupa City.

While not all of the samples tested positive for dengue, many yielded the four dengue strains.

“The blood samples were sent to the virology department of RITM… and the findings showed that all the four zero types were there, so I think that’s the reason for the high number of dengue cases here,” she said.

Dr. Yolanda Oliveros, head executive assistant to Health Secretary Enrique Ona, said it is possible for all the dengue strains to surface in the same year in an area but there is one strain that usually becomes dominant.

“But the danger there is that if all the four types are equally circulating in an area, a person who acquired type A dengue, for example, can again fall ill in the same year with type B, type C or type D if all are circulating,” she told The STAR.

Ideally, a person develops immunity for the same dengue strain that had afflicted him. So with four strains in circulation, no one has this resistance.

This year, the DOH observed a low number of dengue cases in Metro Manila primarily because the strain circulating there is the same as in 2009 – type C.

Sunga said other factors being considered for the dengue outbreak here is the El Niño phenomenon that hit the area early this year and the succeeding rainy season.

In El Niño, the public tends to store water in containers that are not covered so they become breeding sites of dengue-causing Aedes Aegypti mosquitoes.

And during rainy days, clean but stagnant water is abundant in the neighborhood and mosquitoes also tend to thrive there.

Sunga said dengue cases were observed to rise in June but peaked in July. 

From January to July this year, the city health office here had recorded a total of 852 dengue cases, including 12 deaths.

Of these cases, 273 and 363 were recorded in June and July with four deaths each.

During the same period in 2009, only a total of 148 dengue cases were registered here.