Fears that the 1995 and 1998 dengue fever epidemics that struck thousands of Cambodians will recur this rainy season have prompted health officials to begin a massive distribution of a chemical that kills mosquito larvae.
“If we can’t prevent another outbreak this year, then at least we can minimize it,” said Dr Chang Moh Seng, dengue officer for the World Health Organization.
The chemical, a larvicide called Abate, is being put into more than 3.5 million water pots that many Cambodians use for storing water. The mosquitoes that transmit dengue to people—the Aedes albopictus and the Aedes aegypty, commonly known as the tiger mosquito—usually breed in clear, stagnant collections of water.
In 1998—which saw the worst dengue epidemic in the country’s history—there were 16,215 reported dengue cases and 475 reported child deaths, according to the WHO. In 1995, more than 10,000 people contracted the disease and 447 died.
So far this year, there have been 348 people with dengue fever and 12 have died, according to WHO statistics tabulated from 24 provinces.
Dr Beat Richner of Kantha Bopha Children’s Hospital said his hospital saw a large increase in dengue cases in April from the previous month, although it did not reach the number of cases seen in April 1998.
Since Jan 1, Richner’s two hospitals in Phnom Penh have hospitalized 124 children for dengue fever. In Siem Reap, there have been 72 hospitalizations.
Seng Bopha’s father, Seng Run, brought her to Phnom Penh by taxi Sunday from Kompong Thom province. The 11-year-old had vomited blood and complained of stomach pains and a headache.
“My neighbor told me that her child had the same problem and told me that I should go to Phnom Penh,” Seng Run said. “I didn’t know that she had dengue fever until we came here.”
Kantha Bopha’s Dr Laurent Denis said that Seng Bopha does not have a severe case of dengue, but she will be monitored for several days. Sometimes the condition of a person sick with dengue “can go from very good to very bad very quickly,” he said.
The black-and-white striped mosquitoes that carry dengue bite during the day only, with the highest risk to people occurring just after dawn and in late afternoon.
Dengue usually affects small children and foreigners who have not built up resistance to the disease. It generally peaks during the rainy season, especially in August, because of the enhanced breeding conditions provided by dampness.
Because the tiger mosquito lives its entire life within a small area, dengue is most common where population is dense. As a result, cities like Phnom Penh and Battambang have been the traditional epicenters for outbreaks.
In Phnom Penh, the Tonle Bassac, Russei Keo, Stung Meanchey and Tuol Kok districts are considered high-risk because people live close together and use water storage pots, and because there is a large number of discarded cans, plastic bags, tires and coconut shells that can hold water and act as a breeding ground.
Dengue usually is accompanied by fever, muscle pain and red spots the size of pin pricks. A child will bruise easily as the virus begins to destroy the blood-clotting system.
In a severe case of dengue, the virus breaks down the walls of blood vessels, causing blood to leak throughout the body. Shock results from this, which can be deadly if not treated with immediate blood transfusions.
Parents should put mosquito repellent on their children during daylight hours and consult a doctor if the child starts to run a high fever.
There are four strains of dengue, and a bout with one strain results in permanent immunity from that strain and a temporary cross-immunity to the other three strains. That wears off after several years, according to Dr Stefan Hoyer, WHO medical officer for malaria control, which helps explain why epidemics have been occurring in three-year intervals since 1992.
“Every epidemic has been worse than the last one,” he said.
More than 1,000 people in 13 provinces are distributing the larvicide, which is mixed into water in doses that are harmless to people. The $500,000 campaign, which will continue through August, is being funded by the International Federation of Red Cross and Red Crescent Societies, USAID and the WHO.