MEXICO CITY - The deadly hemorrhagic form of dengue fever is increasing dramatically in Mexico, and experts predict a surge throughout Latin America fueled by climate change, migration and faltering mosquito-eradication efforts.

Overall dengue cases have increased by more than 600 percent in Mexico since 2001, and worried officials are sending special teams to tourist resorts to spray pesticides and remove garbage and standing water where mosquitoes breed ahead of the peak Easter week vacation season.

Even classic dengue - known as "bonebreak fever" - can cause severe flulike symptoms, excruciating joint pain, high fever, nausea and rashes.

More alarming is that a deadly hemorrhagic form of the disease, which adds internal and external bleeding to the symptoms - is becoming more common. It accounts for one in every four cases in Mexico, compared with one in every 50 seven years ago, according to Mexico's Public Health Department.

While hemorrhagic dengue is increasing in the developing world, the problem is most dramatic in the Americas, according to the Centers for Disease Control and Prevention (CDC).

Dengue is driven by longer rainy seasons some blame on climate change, as well as disposable plastic packaging and other trash that collects water. Migrants and tourists - including the many thousands of Americans expected for spring break this year - carry new strains of the virus across national borders, where mosquitoes can spread the disease.

The CDC says there's no drug to treat hemorrhagic dengue, but proper treatment, including rest, fluids and pain relief, can reduce death rates to about 1 percent.

Latin America's hospitals are ill-equipped to handle major outbreaks, and officials say the virus is likely to grow deadlier, in part because tourism and migration are circulating four strains across the region. A person exposed to one strain may develop immunity to that strain - but subsequent exposure to another strain makes it more likely the person will develop the hemorrhagic form.

Mexico's Public Health Department has sent hundreds of workers to the resorts of Puerto Vallarta, Cancún and Acapulco to try to avert outbreaks ahead of the Easter week vacation.

"We are working intensively, both the federal and state governments, on [these] three sites that we want to keep under control, so that it doesn't become a risk for tourists," said Pablo Kuri, head of Mexico's National Center for Epidemiology and Disease Control.

The Canadian Embassy in Mexico City issued an alert about dengue after five Canadians were sickened in Puerto Vallarta this year. Acapulco, a city of 700,000, has documented 549 cases of classic and hemorrhagic dengue in the first two months of 2007, up from 86 in the same period last year.

Dengue is mostly a problem in tropical slums, where trash collection and sanitation are not as good as in tourist areas.

In January and February, Mexico's dry season, there were 1,589 cases of both types of dengue nationwide, up 380 percent from the same period in 2006, Kuri said. And last year was also bad for dengue: Mexico documented 27,000 infections overall - including 4,477 hemorrhagic cases and 20 deaths - compared with 1,781 cases overall in 2001.

Dengue has been found along the U.S.-Mexico border, where 151 classic and 46 hemorrhagic cases were recorded last year in the Gulf state of Tamaulipas, south of Texas.

A 1922 outbreak in Texas infected a half-million people. And according to the CDC, dengue returned to southern Texas in 1980 after a 35-year absence. Occasional cases since then have included hemorrhagic dengue.

The global solution to dengue outbreaks is mosquito control, and faltering eradication efforts, together with climate change, probably share blame for dengue's rise in the Americas, Kuri said.

A successful eradication program in Latin America in the 1960s sent the disease into remission, but economic crises and government downsizing sapped those efforts over the next two decades.

Paraguay declared a state of emergency in March after 17 people died of hemorrhagic dengue and an estimated 400,000 were infected with the milder "classic" form of the disease. The government sent soldiers into the streets in an emergency campaign to spray insecticides and clean up stagnant water.

At least 24 people died of hemorrhagic dengue in the Dominican Republic last year.