San José, Costa Rica, since 1956

Dengue Exploding Countrywide

Anti-malarial pills were once a must in visitors’ suitcases alongside the Hawaiian shirts and guidebooks, especially if the itinerary called for travel to Costa Rica’s southern and Atlantic regions.

But today’s record-high dengue infections have made it the most dreaded mosquito-borne disease.

Dengue’s porters, the Aedes aegypti mosquito, have caused a 408 percent surge in Latin American cases during first six months of 2010 over the same period last year. In Costa Rica, 10,788 cases have been reported from January-June, nearly 4,000 more than all of 2009.

While the effects of dengue aren’t as severe as its mosquito-transmitted sister malaria, it can be deadly. In Costa Rica, 19 people have died of dengue since 1993, with one death so far in 2010.

Dengue has had outbreaks in Costa Rica every two or three years: 2005 was the worst in the past decade with 37,798 cases nationwide, followed by 2007, with 26,504 cases and 2003, which saw 19,703.

Rodrigo Marín, national dengue control coordinator, said the disease is emerging where it hasn’t existed before, which means many people are not aware they are at risk. The combination of 2010’s hot summer with an early rainy season is proving a serendipitous recipe for the aegypti’s population explosion.

“Weather conditions have been very flattering to the proliferation of the vector Aedes aegypti (mosquito) … and the Central American sub-region … is already seeing an increase in dengue transmission that can potentially affect large population groups,” read a July 7 World Health Organization outbreak alert.

In past years, Costa Rica’s Pacific and Caribbean coastal regions and low-lying areas have typically been the hardest hit by dengue. But this year, the Central Valley has seen a record 2,000 dengue cases.

Few Costa Rican regions have seen an outbreak like Santa Cruz on the NicoyaPeninsula in the northwestern Guanacaste province. The sparsely populated area has already reported more than 2,000 cases, prompting the cancellation of next weekend’s Annexation Day festivities whose bull runs are popular with tourists. Health officials want to avoid an influx of people to the area due to the high concentration of infected mosquitoes that may bite visitors and further increase the disease’s spread to other parts of the country.

Juan Luis Sánchez, regional medical director for the health ministry said, “We are hoping the actions the Health Ministry is taking will achieve their desired result.” Sánchez’s office is based inside the small Santa Cruz government clinic that has recently been seeing up to 70 dengue patients a day.

Guanacaste’s seasonal dry conditions mean that farms and homes regularly store water as a reserve for water shortages. And clean, standing water is the preferred breeding environment for the aegypti mosquitoes.


Malaria vs. Dengue


Malaria, a serious, sometimes fatal disease, is treatable with medicine and also readily prevented by anti-malarial pills taken before and during visits to risk areas. Also, since its vector, the Anopheles albinus mosquito, tends to bite at night and prefers rural, unpopulated areas, sleeping under a mosquito net at night helps to prevent infection.

Dengue’s carriers, on the other hand, tend to bite during the day and proliferate in urban settings. In dengue risk areas, prevention involves active and consistent measures including wearing long-sleeved shirts and long pants, and using insect repellent. Napping with a net is also important, since the aegypti bite during the day (see information box).

Malaria has waned here because of controls over the anopheles mosquito, according to Marín, the national dengue control coordinator. From a high of nearly 7,000 malaria cases reported by the Health Ministry in 1992, malaria has nearly been eliminated in Costa Rica.

“Costa Rica is actually in a state of pre-eradication (when it comes to malaria), with only 72 cases this year,” Marín said.

As for dengue, Marín said many cases go unreported, as there is not one specific telltale symptom or reaction to dengue. Sometimes it’s high fever, other times its body aches or vomiting, sometimes it’s a sharp pain behind the eye, and symptoms vary according to a person’s age, with young children usually affected more mildly than adults.

For Jerry “Bubba” Hallstrom, known for his popular fishing report (often published in this paper), it was high fevers with mild hallucinations, sweats, chills, no energy and no appetite that led him to seek medical attention.

“Dengue is one of the worst things I have had to get over,” said Hallstrom, a resident of Jacó, who has now had it twice. “It makes you realize how strong people are who have to live in pain every day because of chemotherapy or other illnesses.”

Hallstrom never felt a bite, doesn’t remember being bit, and said he is at a loss as to how to protect himself in the future.

“You can keep your yard free from mosquito puddles, but you can’t do anything about your neighbors’ yard or your neighbors’ neighbors’ yard,” he said.

So for travelers used to arming themselves with pills as they head to the tropics, guarding against dengue will take a lot more work and presence of mind.


Fact Box

What is dengue?

Dengue fever is caused by one of four viruses transmitted mainly by the Aedes aegypti mosquito found in warm climates. Dengue hemorrhagic fever, a potentially lethal complication of dengue, is thought to occur upon re-infection with a different strain of the disease. From 50-100 million cases of dengue arise worldwide each year, and two-fifths of the world’s population is at risk for infection.

Aedes albopictus, another dengue-transmitting mosquito, has recently been introduced from Asia to the Americas mainly through the used-tired trade, as old tires are their favored breeding ground.

What are the signs and symptoms?

Symptoms of dengue begin four to six days after infection and can last up to 10 days, with complete recovery taking up to a month. Dengue fever is a severe flu-like illness that usually starts with a sudden high fever, and can include severe headache, pain behind the eyes, muscle and joint pain, and rash. Nausea, vomiting and loss of appetite are also common. Older children and adults are usually sicker than young children.

Most cases are mild, but some can progress to dengue hemorrhagic fever in which blood vessels leak and cause bleeding from the nose, mouth and gums as well as internal bleeding. Bruising can be a sign of internal bleeding. Hemorrhagic dengue requires immediate hospitalization, as it can cause shock and is fatal in around 5 percent of cases.

How is it treated?

There are no medications for the disease besides pain relievers (a non-aspirin form only), rest and fluid intake. If symptoms worsen, medical consultation is advised.

Is there a vaccine?

Development of a dengue vaccine is in progress, but is not expected soon.


People infected with dengue should use mosquito nets, as mosquitoes acquire the virus from humans during two-seven days of the infection when the virus circulates in their blood, mainly while with fever. Mosquito breeding can be controlled by eliminating or covering all areas where water collects, including in flowerpots, buckets, discarded tires, animal water bowls, empty bottles and food containers or other trash. In tropical areas, wear long sleeves, use insect repellent and sleep under mosquito nets.


SOURCES: The World Health Organization (WHO), and the Centers for Disease Control and Prevention (CDC) and Directors of Health Promotion and Education, both based in the U.S.

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