WORLD HEALTH DAY: South American Arms Race Against Dengue

By IPS Correspondents Reprint | | Print |

Raúl Pierri*

MONTEVIDEO, Apr 7 2007 (IPS) - In the face of the current outbreak of dengue fever in several countries of South America, infrastructure for detecting cases has become a top priority. But laboratories do not obviate the need for clinical diagnosis by skilled health professionals.

In the face of the current outbreak of dengue fever in several countries of South America, infrastructure for detecting cases has become a top priority. But laboratories do not obviate the need for clinical diagnosis by skilled health professionals.

World Health Day, which is celebrated Saturday, is dedicated this year to the question of international health security in the face of outbreaks of emerging and rapidly spreading diseases, biological or radioactive accidents, and natural disasters.

In Paraguay, which since 2000 has equipped laboratories for detecting dengue, most cases are still detected by means of clinical diagnosis. Since the current epidemic broke out in that country in March 2006, 24,781 cases have been reported, of which only 5,000 were confirmed by lab tests, the director general of health vigilance, Gualberto Piñanez, told IPS.

Of the 13 deaths from dengue so far, six were cases of hemorrhagic dengue, five involved gastric dengue, which attacks vital organs, and two were caused by a mixture of both strains.

“Between 100 and 200 cases a day are currently being reported,” said Piñanez. “This reflects a significant drop from the peak of 500 to 600 cases a day in February.”

Although there is neither a cure nor a vaccine for the disease, the symptoms generally abate if the patient follows a regime of complete rest, continued hydration – intravenous in severe cases – and treatment with acetaminophen. Complete recovery can take up to a month.

But hemorrhagic dengue causes intense abdominal pain, nausea and bleeding under the skin and into mucous linings, and gastric dengue, which has begun to appear, attacks vital organs like the liver, heart, lungs or brain and can cause death within hours.

Paraguay experienced a major dengue epidemic in 1988 and 1989, after which the disease did not appear for 10 years. But in 1999, a number of cases were reported, and a new outbreak occurred in 2000. However, the current epidemic is the most serious.

To diagnose a case of dengue fever, blood samples are tested for immunoglobulin M (IgM) antibodies, and to determine the strain of dengue virus, of which there are four, the polymerase chain reaction (PCR) is used.

Until the epidemic of 2000, laboratories in Paraguay were only equipped to carry out exams to detect IgM antibodies. But there are now private and public labs throughout the country that are capable of conducting the PCR test. The main laboratory, which is run by the Public Health Ministry, is in the capital, Asunción. There are labs in areas along the borders with Brazil and Argentina as well.

Argentina also has special labs for diagnosing cases of dengue. Alfredo Seijo, director of the dengue unit at the Muñiz Hospital in Buenos Aires, said there is a “very efficient” monitoring system at both the provincial and national levels.

The Dr. Julio Maiztegui National Institute of Human Viral Diseases in Pergamino, in the eastern province of Buenos Aires, is working on a vaccine for dengue hemorrhagic fever and carries out quality control of lab tests for dengue and other diseases, like yellow fever and arboviral encephalitis, that are carried out in the provinces.

“There are laboratories in practically all of the at-risk provinces” in central and northern Argentina, said Seijo.

The northern province of Salta, which borders on Bolivia and has been hit hard by dengue outbreaks in the past, now has four laboratories. There another four in Buenos Aires, which can carry out quick, reliable diagnostic tests, he said.

Uruguay – which along with Canada is the only country in the Americas free of autochthonous dengue contracted from local mosquitoes – does not yet have PCR labs, so blood samples are sent to the Centre for Disease Control in Puerto Rico.

The delays involved in confirming cases of dengue led to a premature report on Mar. 18 that the first case of autochthonous dengue had been detected: a 30-year-old man in the northern department (province) of Salto, who is still in the hospital.

But after receiving from Puerto Rico the preliminary results from 11 PCR samples, which were negative, the Uruguayan Public Health Ministry reported that there were no cases of autochthonous dengue.

The results confirmed that only cases of “imported” dengue have occurred in Uruguay, three of which involved people who were infected in Paraguay and one in Bolivia. In addition, 50 suspected cases of dengue were ruled out and 26 are still being studied.

The Aedes aegypti mosquito was eradicated in Uruguay in 1958, after an 11-year campaign, but it reappeared in 1997.

In the last few years, some 20 cases of dengue have appeared annually in Uruguay. In 2006, for example, a number of Uruguayan soldiers who served in the United Nations peacekeeping forces in Haiti “imported” the disease on their return.

Health authorities said that this year, the Public Health Ministry labs will continue carrying out the IgM test, which may later be conducted by the hospitals themselves. In addition, the Ministry will open a PCR test centre next month.

But in a country like Brazil, where dengue epidemics have occurred over the past 20 years, the problem is not a lack of laboratories equipped to diagnose the disease, but a poorly organised public health system, said Dr. Rivaldo Venancio Da Cunha, a professor at the Federal University of Mato Grosso do Sul and a member of the Health Ministry’s dengue advisory committee.

The only fast, efficient way to diagnose dengue in a city with thousands of cases is clinical diagnosis, which depends on the ability of doctors and other experienced health professionals to recognise the symptoms. Lab tests are only carried out in extremely serious or doubtful cases, said Da Cunha.

Brazil’s latest epidemiological bulletin, from Mar. 26, points to an aggravation of the epidemic in Brazil, with 234,909 suspicious cases notified to the Health Ministry this year, and a 39 percent increase in just one week.

The state of Mato Grosso do Sul, on the border with Bolivia and Paraguay, accounts for 41 percent of all cases in the country (55,567, of which 46,082 are in the capital, Campo Grande).

So far, there have been 124 cases of hemorrhagic dengue in Brazil, none of which occurred in the south, and 17 deaths.

Brazil has been unable to get the population of Aedes Aegypti mosquitoes under control, even though the Health Ministry has a system to monitor the density of the mosquitoes in each neighbourhood, town or city, which enables it to predict where outbreaks are likely to occur.

The first mentions of dengue in cities in Brazil date back to 1916 and 1923. But the first epidemic that was confirmed by lab tests occurred in 1981-1982 in the northern state of Roraima, on the Venezuelan border, and in 1986 in Rio de Janeiro, from where it spread to other states in the following years.

Since then, strains 1, 2 and 3 have been detected in Brazil, and there are fears that strain 4, the most deadly, will appear.

In Bolivia, aid from Cuba has been essential in controlling the epidemics generated by the recent flooding in the eastern Amazon jungle region, where a health emergency is still in place, the Health Ministry head of epidemiology, René Barrientos, told IPS.

Last year, public opposition to ties with Cuba blocked plans to set up a Cuban laboratory in Trinidad, the capital of the northeastern department of Beni, the area hardest hit by the flooding from December to March.

Since January, Barrientos’ office has registered 3,900 cases of dengue, 90 percent of which have occurred in the eastern department of Santa Cruz, and the remaining 10 percent in Pando, Beni and Chuquisaca. One of the victims died of hemorrhagic dengue, which has affected 12 patients.

The number of cases has thus risen tenfold, from the 400 a year on average documented in the last few years, said the official.

Four labs set up by the Cuban government in Santa Cruz de la Sierra, Trinidad, Pando and Tarija have helped make quick diagnosis of diseases possible through “ultramicroanalysis”, without any cost to the patient.

The severe flooding has led to the spread of dengue, leptospirosis, hanta virus and respiratory infections. An outbreak of malaria is also expected, once the water levels go down in the tropical regions, according to the Bolivian Health Ministry.

The first epidemic of classic dengue documented in laboratories in the Americas affected the Caribbean and Venezuela in 1963 and 1964. In the 1980s, Bolivia, Brazil, Ecuador, Paraguay and Peru suffered their first outbreaks. And in 1981, Cuba reported the first case of hemorrhagic dengue in the hemisphere.

* With additional reporting by Marcela Valente in Argentina, Franz Chávez in Bolivia, and Mario Osava in Brazil.