Development & Aid, Headlines, Health, Latin America & the Caribbean

HEALTH-SOUTH AMERICA: Yellow Fever Takes Heavy Toll

Humberto Márquez

CARACAS, Sep 15 2003 (IPS) - Outbreaks of yellow fever have claimed the lives of 84 people in five South American countries so far this year, despite the vigorous fight to eradicate the mosquitoes that spread the disease in the countryside and to prevent them from reaching the cities.

Colombia has been hardest hit, with 82 cases of infection reported and 33 deaths. Brazil follows with 62 cases and 23 deaths, Venezuela 21 and 15, Peru 15 and nine, and Bolivia with six reported cases and four deaths, according to the Pan-American Health Organisation (PAHO).

"These are recurrent outbreaks of jungle yellow fever, concentrated in the Amazon, Orinoco and Magdalena river basins, and others in South America, as well as in tropical Africa," PAHO epidemiologist Mario Valcárcel told IPS.

Yellow fever is a serious infectious disease that can cause liver damage and congestion of the gastric and intestinal tracts. In addition to high fever, it produces jaundice (the origin of the "yellow"), vomiting, muscle pain and headache.

According to the World Health Organisation, based on global statistics, most people who are infected with the virus recover in three or four days, but 15 percent enter a "toxic phase" in which kidney function deteriorates, some patients bleed from the mouth, nose and eyes. Half who reach the toxic phase do not survive the illness.

Humans are infected when they "enter the cycle involving the arbovirus, the virus-transmitting mosquito and the monkeys that carry the disease."

The leading diseases spread by mosquitoes in the tropical regions of the Americas are dengue, yellow fever and malaria, says Valcárcel, who works with PAHO’s Caracas office.

Thousands of people are infected with dengue each year, compared to the dozens or several hundred infected with yellow fever. But in the case of latter, "the problem is the high ratio in terms of the number of people infected and the number who die," said Valcárcel.

Venezuela’s health minister María Urbaneja said that South America "has niches of jungle yellow fever, transmitted by the Aedes haemagogus mosquito, but in the region we haven’t had urban yellow fever (transmitted by the Aedes aegypti, which is also the vector for dengue) since 1942."

In Colombia, the Ministry of Social Protection declared a health emergency in the northeastern department of Norte de Santander, the centre of the biggest yellow fever outbreak in this country in the past 50 years.

The emergency declaration streamlines paperwork for launching a vaccination campaign aimed at the 1.9 million people living in this area along the Venezuelan border.

Douglas Natera, president of the Medical Federation of Venezuela, called for the same sort of declaration in his country, but one that covers the entire nation, not just the areas at greatest risk.

At the same time, the Medical Federation, a group opposed to President Hugo Chávez, began organising "immunisation days" in some of the middle-class districts of eastern Caracas.

But minister Urbaneja refused to issue a health emergency declaration for the whole country and ordered a halt to vaccine deliveries for the federation’s "selective" immunisation campaign.

"We cannot allow this situation to be used for political ends, or that it disperse our public health efforts. Our duty is to focus on the high-risk areas and continue vaccinating children six to 12 months old," she said.

The agent behind this potentially fatal disease is the "Charon evegatus" virus. There is only one type of vaccine to prevent infection. It is based on "attenuated", or weakened strains of the virus, which are enough to build the organism’s defences against the disease.

The Venezuelan government turned to the PAHO revolving fund for vaccines in order to purchase as many as six million doses from Brazil and France. The vaccines, costing five million dollars, are earmarked for the residents of the municipalities at high-risk of yellow fever, and for those who must travel to those areas.

Urbaneja said the vaccination campaign is concentrating "on seven states in the west and south of the country, where 3.2 million people live, and on another two million who live in medium-risk zones."

But not where the majority of Venezuela’s population of 24 million live, in the central and northern regions, "who are at low risk," she assured.

Valcárcel said he agrees with "what the governments of Venezuela, Colombia and Brazil are doing, because it is what is indicated by PAHO in these cases: focusing efforts on the areas and the population groups at highest risk."

The arbovirus that causes yellow fever mostly affects monkeys, particularly the red howler monkey (Alouatta seniculus). A mosquito that has bitten an infected monkey spreads the disease by biting a human.

"This is why it is so important to track what is known as ‘the silence of the forests’. When the loud howler monkeys begin to die it is a sign that yellow fever is advancing, and it is vital to prevent it from reaching the cities," Valcárcel said.

Many of the symptoms of yellow fever are the same for malaria and dengue: high fever, chills, muscular pain, headache, loss of appetite, nausea and vomiting. Most people recover through treatment involving intravenous liquids, as well as dialysis for renal insufficiency.

Many of the deaths from the disease occur because the infected individual has not received treatment in time or because there are no laboratories available to correctly diagnose the illness.

The most effective means of fighting the disease is through vaccinations, which can be effective from 10 years to a lifetime.

The vaccine must be kept refrigerated at four degrees Celsius. In the case of the outbreak in the Colombia-Venezuela border region, the problems of refrigeration, transportation and application are compounded by the presence of the illegal armed groups that fight among themselves and against security forces.

It is a vast area that the Colombian army and police try to control, as leftist guerrillas, right-wing paramilitaries and drug traffickers battle for dominance.

"It is a very long border (2,219 km), with warring groups that complicate the task of vaccination and cause the displacement of persons who flee the conflict," said minister Urbaneja. Six of the people who died of yellow fever in Venezuela this year came from Colombia.

The violence of the border region also creates obstacles for carrying out epidemiological and virus monitoring efforts. "There is the danger that the health workers will be trapped in the armed conflicts," pointed out PAHO’s Valcárcel.

The fight against yellow fever, he said, involves the collaboration of laboratories in all of the affected countries, and shortly Guyana is expected to join. Ideally, monitoring endeavours should cover all countries of the Amazon Basin.