America's latest health threat is not carried by a bioterrorist but a mosquito.
So far this year, the so-called West Nile virus has spread farther and caused more fatalities than anthrax. It's an example, experts say, of how diseases have become globalized.
Thanks to increasing travel and trade, diseases as new as AIDS and as old as malaria are jumping continents and oceans faster than ever before.
That means that even developed countries, such as the United States, have to bolster their public-health infrastructure to meet the challenge. But the demand comes at a difficult time for cash-strapped states and localities, which traditionally have provided the first line of defense against mosquito-borne pathogens.
"Unfold a map and close your eyes and point: Virtually any place can be reached within 36 hours," says Madeline Drexler, author of "Secret Agents: the Menace of Emerging Infections." "And if you can get there, so can a virus.... West Nile virus shows how globalized infectious disease has become."
The virus is an unusual attention-getter. Found to be fatal only in very rare cases, it has nevertheless spread rapidly. Since its first detection in the US three years ago in New York City it has moved through the South, the Midwest, and possibly as far west as Colorado.
The federal Centers for Disease Control (CDC) reports that even in areas where the virus is present, very few mosquitos carry it. Even then, fewer than 1 percent of people bitten by an infected mosquito get severely ill.
Nevertheless, 11 fatalities, mostly in Louisiana, have been attributed to the virus.
"This is a serious problem," says Lyle Petersen, deputy director for the CDC's division of vector-borne infectious diseases. "Should we be deathly afraid? Absolutely not."
States and localities are stepping up monitoring programs and mosquito-control. The monitoring programs, where state and local officials track dead birds and other animals for signs of the virus, appear to be tracking the spread of the pathogen fairly well. More questionable are mosquito-control programs.
Some states, such as Florida, Texas, and, ironically, Louisiana, have done a good job maintaining their control programs, Dr. Lyle says. Others have let their programs deteriorate as the threat of serious mosquito-borne diseases has receded in recent decades.
The reappearance of a serious threat comes at a bad time for budget-strapped states.
Louisiana, for example, last week announced it would have to go into temporary debt to finance a $3.4 million public-education and control program. According to state law, Louisiana will have to cut other programs later this year to stay within its budget. The CDC has given the state another $3.4 million to fight the problem.
The bulk of the eradication effort typically falls to counties.
Here in St. Louis County, Mo., which has seen half a dozen cases of illness from the virus, the county has stepped up spraying. Officials admit that's the least effective control measure. But the county is also boosting efforts to treat areas where the insects breed, such as sewers and ponds. "It can be a large puddle of water that is wet long enough for mosquitos to lay eggs and breed," says Ron Twillman, a county health department official.
"It does come down to a local issue," says Tom Schafer, spokesman for the public health department in neighboring Illinois. So far, mosquito control has been largely confined to the Chicago area. That may change, since Illinois experienced its first West Nile human fatality last week. But state cash woes have cut into the health department budget. Even with an infusion of $30 million in federal money to fight bioterrorism which will also help in the fight against West Nile the department still faces an overall 5 percent cut this year.
The budget shortfall mirrors the larger challenge facing all public-health efforts in the US. "The American public health system has been languishing for decades," says Ms. Drexler. Even last year's response to the anthrax scare, which infected only a small number of people, stretched the nation's public-health system to the limit, she adds.
Many scientists believe more virulent diseases could appear or reappear on American shores if the nation doesn't maintain its vigilance.
The public also plays a role in prevention, health officials stress. With West Nile virus, for example, citizens need to eliminate mosquito-breeding areas on their own property, they say. These can range from stopped-up gutters to children's pools that haven't been used for a while to something as simple as a piece of aluminum foil left on the ground, which catches water.
"We're looking at neighborhood activities having a major effect," says Phil Nixon, an entomology specialist at the University of Illinois extension service in Urbana, Ill.