HEALTH-BRAZIL: Dengue Epidemic under Control, But Threat Remains

By Mario Osava Reprint | | Print |

Mario Osava

RIO DE JANEIRO, Apr 29 2002 (IPS) - The dengue epidemic that claimed 56 lives in Rio de Janeiro state so far this year is under control, announced Brazil’s Health Minister Barjas Negri, but experts and the population fear a new outbreak.

Of 190,634 dengue cases recorded from Jan 1 to Apr 24, official figures indicate that 1,645 involved the haemorrhagic type, the most serious strain of the disease. The largest previous dengue epidemic in Rio de Janeiro was in 1991, with 85,891 cases.

The mortality rate attributed to dengue could rise because investigations of some deaths have not yet concluded.

Negri considers the epidemic to be practically eliminated, given the decline in dengue cases in Rio de Janeiro, the city hardest hit by the disease in Brazil. The number of ill here in the first 24 days of April was a relatively low 2,684, compared to 37,417 in March, reported the Municipal Health Secretariat.

Negri, a federal-level minister, announced late last week the demobilisation of 1,300 army and air force troops who participated in the campaign throughout Rio de Janeiro state to eradicate the Aedes aegypti mosquito, which transmits dengue.

Furthermore, some 1,000 members of the Health Ministry staff will return home. They have been in the Rio area since February to take part in the anti-dengue and anti-Aedes aegypti offensives.

The health campaign also included the work of volunteers. Some 730,000 people mobilised for the war against the disease- transmitting mosquito on Mar 9, a decisive day for the statewide action.

The sharp reduction in contagion is evident in the smaller numbers of patients in the hospitals, but is due in large part to help from nature. The months of March and April, usually the rainy season for Rio de Janeiro, were the driest in recent years.

The Aedes aegypti requires warm weather and stagnant water to reproduce. Dengue epidemics tend to erupt during rainy summers in tropical countries, and the number of infected persons naturally diminishes as the temperature cools and there are fewer mosquitoes.

The high incidence of the disease left a large portion of the state’s population immunised against dengue Type 3, cause of the latest epidemic.

Once an individual is infected with a strain of dengue, he or she is made immune to that strain. As such, the conditions are running out for maintaining a high level of cases, said epidemiologist Emilson Migowski, of the Federal University of Rio de Janeiro.

The epidemic this year was of predictable magnitude, said Sergio Arouca, a doctor specialising in public health and municipal secretary of health for Rio de Janeiro, who earlier this year warned that there was a lack of preventive measures for confronting dengue.

The outbreaks are most serious and widespread after the appearance of a new virus because the population does not have the natural defences to limit its dissemination.

This is what occurred in Rio de Janeiro during the latest Southern Hemisphere summer. A year earlier, in December 2000, the Type 3 virus had been identified in the city, for the first time in all Brazil. Virus Types 1 and 2 caused the previous major epidemics.

Now there is fear that the problem will be repeated with Type 4, which is already present in neighbouring Colombia and Venezuela, and in Ecuador. No vaccines currently exist to protect humans against any type of dengue.

Dengue is a global disease that is expanding and changing its characteristics, becoming more virulent and claiming more victims, warned the president of the Brazilian Society of Infectology, Celso Ramos Filho.

The disease is particularly dangerous because it is urban in nature. Cities without adequate sanitation favour the proliferation of the Aedes aegypti, agree Ramos and Arouca.

They point out that it is no longer possible to eradicate the mosquito, which means the disease must be confronted with ongoing actions that are “not exclusively medical”.

Basic sanitation and the elimination of precarious housing settlements are essential, according to Ramos.

In some Brazilian cities, like Nova Iguaçú and Niteroi, in the Rio de Janeiro metropolitan area, the mosquito is being combated using bacteria and microorganisms that kill the Aedes aegypti larvae.

This technique was developed by Cuba, which is now exporting its experience in fighting dengue after having suffered its own series of epidemics.

Residents of the Rio area, like taxi driver Jorge Oliveira, want the efforts of the so-called “mosquito-killers” to continue. These public employees are entrusted with inspecting and fumigating against the Aedes aegypti in homes and any sites where conditions favour the insect’s proliferation.

In Oliveira’s opinion, the Rio de Janeiro dengue epidemic this year was due to the fact that the Health Ministry laid off 5,800 mosquito-killers in 2001.

As a result, he and other critics have dubbed the former health minister José Serra, now the governing party’s presidential candidate for the October election, “Presidengue”.