Dengue cases up sharply in Latin America, Asia

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Oct 11, 2007 (CIDRAP News) – Global health officials have noted sharp rises in the number of dengue fever cases in recent months, particularly in Latin American, Caribbean, and Asian countries where the disease is endemic.

A recent surveillance update from the World Health Organization's (WHO's) Southeast Asia office in New Delhi reported that Thailand has more than 40,000 cases so far this year, reflecting a 27% increase over 2006, Deutsche Presse Agentur (DPA) reported on Oct 9. Indonesia's total of 100,000 cases represents a 10% increase over last year, and Myanmar has reported almost 12,000 cases—a third more than it reported in 2006.

The Pan American Health Organization (PAHO), which tracks and manages health issues for the WHO in Latin American and Caribbean countries, reported on Oct 4 that the disease is reaching epidemic levels in some of the locations it monitors. In a statement released to journalists, the organization said it has recorded 630,356 cases so far this year, an 11% increase from 2006. Of this year's cases, 12,147 were the more severe dengue hemorrhagic fever (DHF), and 183 cases were fatal.

Dengue fever is a flu-like illness transmitted by certain species of Aedes mosquitoes. Symptoms include headaches, rashes, cramps, and back and muscle pain. DHF, a potentially deadly complication, is characterized by high fever, bleeding, thrombocytopenia, increased vascular permeability, and in particularly severe cases, circulatory failure. No effective treatment or preventive vaccine is available.

The virus occurs in four serotypes, and infection with any one induces immunity only to that serotype, according to the US Centers for Disease Control and Prevention (CDC). A second infection with a different serotype increases a person's risk for DHF.

Jarbas Barbosa da Silva, PAHO's manager of health surveillance and disease management, said in the press release that all four dengue serotypes were in circulation, "which increases the risk for appearance of the most serious forms of the disease—namely, dengue hemorrhagic fever and dengue shock syndrome."

For the first time, Paraguay has reported cases of hemorrhagic fever and deaths from the disease this year, Barbosa da Silva said.

Southernmost Latin American countries have accounted for 60% of the region's dengue cases, with Brazil reporting the most, the PAHO report said. The Andean region has had 19% of the cases, with Columbia and Venezuela reporting the highest numbers. Other countries reporting high rates are French Guiana, Martinique, Costa Rica, and Honduras.

PAHO's report says Mexico has reported 67,563 dengue cases, of which 5,212 involved hemorrhagic fever.

Health officials in Nuevo Laredo, Mexico, on the US border, recently reported 71 pending or confirmed dengue fever cases, according to an Oct 9 report in the Laredo Morning Times.

A recent article in the CDC's Morbidity and Mortality Weekly Report said that dengue fever is gaining a stronger foothold in southern Texas. The report documented the first DHF case in a Texas resident native to the Texas-Mexico border area and found that 38% of surveyed Brownsville, Tex., residents had IgG antibodies to dengue, indicating that a substantial proportion of the city population had been infected with the virus.

Puerto Rico's health department is recording 500 cases a week, with a cumulative of 6,175 cases and 4 deaths this year, according to a Reuters report. Local press reports in the Dominican Republic say the country has logged 6,000 cases and 30 deaths.

PAHO noted that one contributing factor is waste tires and dumps filled with discarded plastic that create potential breeding sites for mosquitoes.

In July, the WHO's Western Pacific regional office in Manila warned countries in the area that a major dengue outbreak could occur unless they quickly undertook coordinated efforts to curb the spread of the disease. The WHO said the disease had arrived earlier than usual, but it was difficult to estimate the magnitude of the outbreak because official information from most of the counties was incomplete.

John Ehrenberg, a WHO regional adviser, said several factors were contributing to the spread of dengue: population explosion, migration, and rapid urban growth, all of which strain public health services and access to clean water.

"People exposed to these settings often rely on containers to collect water for their own drinking supply. These containers can become mosquito-breeding sites," he said. "Water storage practices are therefore a key target of dengue prevention and control programs."

See also:

Aug 9 CIDRAP News story "Dengue fever expanding its foothold in Texas"

July 23 WHO Western Pacific Regional Office press release

Jun 21 Eurosurveillance report on dengue status and implications for Europe

CDC information on dengue fever and dengue hemorrhagic fever
http://www.cdc.gov/dengue/

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