Dengue fever conquered? Apparently not

WASHINGTON — Anna Manzanarez was a picture of good health. But about a week after catching what she thought was a bad case of the flu, the 28-year-old waitress from Seaside, Calif., collapsed getting out of the shower.

The next day, despite intensive care at a hospital, she died.

Her death shocked her family, but the discovery of what killed her hit public-health officials like a bolt from the blue: She had fallen victim to a virulent form of a mosquito-borne disease that long ago had been eradicated in the U.S. and once was close to being eliminated throughout South America as well.

The disease, dengue fever, is on the march again and beginning to make its presence felt in the U.S., with cases popping up in Texas, Hawaii and Puerto Rico. Last week, top health officials warned that a "widespread appearance" in the continental U.S. is "a real possibility."

Thus far, cases of dengue fever in North America — where disease scientists thought they had conquered it 30 years ago — have tended to be scattered and affect relatively few people. But increased travel to and from South America, where a resurgence has made dengue widespread, is thought to be boosting the disease's spread northward. And some experts suspect climate change is aggravating the problem.

"It's starting to creep up from South America to the Caribbean," said Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases. "If it can occur right at the tip of Texas, a disease which maybe people never heard of could actually appear here."

Fauci, who helped lead the government's efforts against AIDS, sounded the alarm on dengue in an article this month in the Journal of the American Medical Association. He and his science adviser, Dr. David Morens, said more than 760,000 cases were reported in the Americas last year, of which some 20,000 involved the virulent form, known as dengue hemorrhagic fever. That is what killed Manzanarez.

Globally, "it ranks among the most serious infections, but most Americans don't even have it on their radar screens," Fauci said.

No vaccine

There is no vaccine against dengue, nor is there a drug that can cure it, although a race to develop both seems to be gathering momentum. Doctors rely on the patient's immune system to fight off the virus, and most people who get the less-virulent forms of the virus recover, although many have the pains that have given dengue its nickname, breakbone fever.

Hawaii had an outbreak in 2001. Puerto Rico had 10,000 cases last year, and in recent years there have been several cases on the Texas side of the U.S.-Mexico border. Manzanarez apparently contracted the disease on a vacation in Mexico; she died May 9, 2005.

All four types of dengue are found in the Americas, and the two types of mosquitoes that transmit it are present in the U.S. Dengue cannot be passed directly from person to person. After biting an infected person, a mosquito transfers the virus when it bites a healthy person. Theoretically, an infected traveler who returns from South America could spark an outbreak here.

The likelihood of such a scenario developing is the subject of a spirited debate among scientists. So is the role that global warming might play in expanding the range of the two mosquito species that carry the virus: Aedes aegypti and Aedes albopictus (also called the Asian tiger mosquito).

"We really don't know"

Dr. Lyle Petersen, of the Centers for Disease Control and Prevention, said there was "clearly a problem" along the border with Mexico. But Petersen, head of the CDC branch that handles diseases transmitted by insects and other animals, disagreed with Fauci on the chances for widespread outbreaks in the rest of the country.

"The big issue is, will this extend beyond the border into the continental United States? The answer is, we really don't know," Petersen said. "Chances are that the risk at the current time is probably not too great."

The reason, he said, is that the most efficient carrier of the virus — Aedes aegypti — is losing ground because of mosquito-control efforts. But Fauci noted that the second mosquito — the Asian tiger — first was seen in the U.S. in 1985 and now can be found in 36 states.

The areas that could be most susceptible to outbreaks would have to have the right combination of heat and humidity for mosquitoes to thrive; they include the Gulf Coast and parts of the Southeast.

However, a renowned dengue expert at the University of Hawaii, Duane Gubler, dismissed the role of warming as "junk science." He cited other factors in the spread of dengue, such as increased global travel and the rise in the tropics of large cities with sprawling slums.

Gubler said America's high standard of living offered protection from dengue, because homes have screened windows and air conditioning. Yet Americans have shown that whatever their houses may be like, they are not immune to diseases associated with insects and the outdoors. Lyme disease, a bacterial infection spread by tiny deer ticks in woods and grasslands, has become a scourge in parts of the U.S.

And West Nile virus is transmitted to humans by mosquitoes that bite infected birds; it is found in virtually every state and can cause permanent neurological damage.

The vast majority of dengue cases reported in the U.S. — averaging about 150 a year from 1977 to 2004 — involve people who traveled to areas where the disease is found, as Anna Manzanarez did. Details of her death were obtained from a Monterey County coroner's report.