Health & Fitness

From our archives: Looking for the next ‘hot zone’

Editor’s note: Given the interest in deadly viruses with the recent case of Ebola in Dallas, we decided to rerun a condensed version of an article that appeared in the Star-Telegram Sunday Magazine on Oct. 15, 2000.

There’s a killer stalking New York City.

It’s not a person, but a mysterious and deadly virus called West Nile, which has killed eight people and hospitalized at least 76 others since last September. All of these victims were probably infected by simple mosquito bite.

The city is on alert. The most recent case, a 37-year-old Staten Island man, was reported only two weeks ago. Posters proclaiming “The Bite Stops Here,” are plastered on bus shelters, telephone booths, community billboards, sanitation trucks, and in buses and subways. People are urged to wear clothes that cover their arms and legs after dark.

The New York City Health Department has distributed West Nile brochures and fact sheets in 15 languages and placed public-service warnings on radio and television. Storm drains have been treated with three larvicides, and larvae-eating fish were added to city water treatment plants.

Foreshadowing a massive ground-based pesticide campaign, the city shut down Central Park and canceled a New York Philharmonic concert in late July. Health officials had discovered the West Nile virus in the park’s mosquitoes, and proceeded to blanket one of New York City’s largest attractions with insecticide. Trucks then sprayed city neighborhoods and surrounding areas — the last to die of West Nile was an elderly New Jersey man — sending horrified residents running for cover and slamming their windows shut.

Even helicopters have been added to the city’s mosquito-killing arsenal, delivering an airborne attack on the wetlands of Staten Island — more than 40 hard-to-reach lakes, ponds and marshes.

In the meantime, New York’s worried city health officials are conducting a door-to-door campaign, collecting blood samples on Staten Island to get a better estimate of the total number of people infected. Last year, a similar follow-up found that as many as 1,900 people were infected in northern Queens, the New York City borough where the first West Nile case in the Western Hemisphere was identified a little over one year ago.

An information line has handled more than 100,000 calls during the past six months, including hundreds reporting standing water, in which mosquitoes breed, and dead birds. Although the virus is passed between mosquitoes and birds, only mosquitoes pass it on to people.

The scary part is that most people never know they have the disease, which causes flu-like symptoms, unless it develops into encephalitis, an inflammation of the brain.

It all reads like the latest bestselling thriller, except it’s not. It’s real. And it may just be the beginning.

Emerging viruses

Although researchers are tracking mysterious viruses worldwide, and here in Texas, no one knows for sure when the next hot zone will emerge.

West Nile isn’t the only virus that is of great concern to researchers. There are four families of hemorrhagic fever virus — arenaviruses, bunyaviruses (hantavirus), filoviruses (Ebola) and flaviviruses (West Nile, dengue) — that merit a close watch. How frightened should we be of these viruses? Researchers say it’s difficult to know when and where they will strike, but they all agree that being ready for them is the key to containment.

When people think of a hemorrhagic fever virus, which causes severe internal bleeding, a high fever and shock, the one that’s most likely to come to mind is Ebola. Ebola triggered paralyzing fear when it stalked the rain forests of northern Zaire and southwestern Sudan in the early ’90s, killing hundreds of people; the fear struck home when Ebola became airborne and began killing monkeys at a medical research facility near Washington, D.C. Four hundred and fifty monkeys were destroyed to contain that outbreak.

Then Ebola crept even closer, expanding into Texas in April 1996, when the virus was diagnosed in three monkeys shipped from the Philippines to the Texas Primate Center in Alice, south of San Antonio. All 100 monkeys in that shipment eventually were destroyed, but that strain of Ebola, like the one found in the Reston, Va., monkeys, turned out to be harmless to humans.

Scientists still do not know the origin of Ebola or exactly how it is transmitted or why certain strains are deadly to monkeys, others deadly to people, and some deadly to both.

Exotic new and re-emerging viruses, including several that cause hemorrhagic fever, are lurking in rats, mice, ticks and mosquitoes throughout the United States.

No one knows when or why they go looking for human hosts; no one knows just how close the hot zone is, said Dr. Charles Fulhurst, a virologist at the University of Texas Medical Branch in Galveston, during a visit to his lab.

“Every time you turn around, someone’s finding a new communicable disease, “ he says.

Hantavirus outbreak

The UT Medical Branch at Galveston, which is now building one of the most sophisticated high-tech biohazard labs in the country, has long led research on tropical diseases transmitted by mosquitoes, ticks and rodents.

One of the high priorities is the Sin Nombre hantavirus, which first jumped from deer mice to people in 1993 in New Mexico. The outbreak quickly expanded through the Four Corners region, into Colorado, Arizona and Utah. It has now spread to more than 30 states, including Texas, killing 102 of the 260 people who became infected with the virus, most likely by breathing tiny airborne particles of dust contaminated with the rodents’ urine, saliva or feces.

As of the end of August, the Sin Nombre hantavirus had infected 15 people in Texas and killed five of them. It has been identified in five species of mice and rats from 20 counties in Texas.

“More than 1 million people reside in these counties,” Fulhorst says. “We don’t know how many are rural versus urban, but we can say that a substantial human population in Texas is at risk of hantavirus infection.”

Working with a field team from Texas Tech University, Fullhorst found the virus in 133 of the 3,000 rodents collected and tested at UTMB under a grant from the Texas Higher Education Coordinating Board.

“In at least 20 counties, we now know hantavirus is naturally occurring. … But, the evidence is that hantavirus has been here a long time — millions of years — in a lot of different rodents,” Fulhorst says.

Two teen-agers — one from Amarillo, one from Lubbock — were stricken this summer with Sin Nombre hantavirus. Both recovered.

‘Important to be ready’

Another viral outbreak of concern to Texas researchers, this one of dengue fever, occurred in Texas last year, with 62 cases reported, including one death. Five people have been hospitalized in Texas with dengue fever so far this year, says Julie Rawlings, chief epidemiologist with the Texas Department of Health. All five cases are believed to be “imported,” brought back from travels in Central and South America. There have been no deaths.

That’s not all. On Aug. 30, Rawlings confirmed this year’s first case of St. Louis encephalitis in Texas. A team from the Texas Department of Health was dispatched to the Lake Livingston area in far East Texas to assess the situation and determine whether insecticide spraying is needed to stop the spread of the virus. No cases were reported in the state last year.

The last real outbreak of St. Louis encephalitis was in 1995, when Texas had 22 cases, including 19 in Dallas County.

Both St. Louis encephalitis and dengue (“break-bone”) fever are spread to humans by mosquitoes and are closely related to the West Nile virus.

Texas public health officials have expanded surveillance efforts to include West Nile on the list of diseases being monitored.

Public health officials will be especially vigilant as birds make their annual migration through the South from colder limates in the Northeast.

“It is very important to be ready, to have the tools in hand. Things like arenaviruses and hantavirus are very uncommon in this country, but we need to study them to be ready in case something happens that makes them become common,” says Dr. C.J. Peters, chief of special pathogens at the Centers for Disease Control and Prevention in Atlanta. “We don’t expect to see more than a handful every year, but you don’t know what might happen to change that.”

‘Must always be on alert’

“In the Middle Ages, deadly plagues were shipped from one continent to another — carried by flea-infested rats on board ships,” says Dr. David Heymann, the World Health Organization’s top infectious disease expert.

“Today they travel by plane, carried by airline passengers from one corner of the Earth to the next, all in a matter of hours. An outbreak anywhere in the world must now be treated as a threat to virtually all countries — especially those that serve as major hubs for international travel,” he says.

As the number of international airline passengers has soared from 2 million a year in 1950 to more than 1.4 billion today, the world has been slow to recognize the implications for public health, the WHO official laments.

“Throughout history, only one infectious disease — smallpox — has ever been eradicated,” Heymann points out.

“There seem to be more new and re-emerging viruses today because they can spread faster and because we are doing a better job of identifying them, and because the Internet has opened up surveillance. Nobody can hide anything,” Heymann said in a telephone visit from his office in Geneva.

“We are looking at everything, trying to identify anything unusual as early as possible.”

Right now, the WHO is on the alert for a new influenza virus, he says.

“We’ve been on the verge of another flu virus introduction. We have 110 labs looking out for evidence of new strains, like we almost had with the Hong Kong ‘bird flu’ in 1997. We must always be on alert, constantly looking, trying to prevent anything from slipping through,” Heymann says.

‘Frightening and very dangerous’

Vaccines were supposed to have triumphed over deadly viruses by now, but at least 30 new infectious diseases have been identified in the past 20 years, according to the World Health Organization.

Infectious disease is the leading cause of death worldwide.

Infectious diseases are considered new or emerging when they are new to people, begin occurring more frequently or spread to new locations.

Some are truly new. Some, like hepatitis C, have been around for years but only recently have been identified. An estimated 100 million people are infected with hepatitis C.

Usually, viruses develop in isolated populations. They don’t spread far because they kill so rapidly they have no time to get outside, but others, like hepatitis C and AIDS, have long incubation periods. AIDS took a long time to discover and had already spread widely before we knew it was here. At the end of 1999, 33.6 million people worldwide were living with HIV, the virus that causes AIDS, the World Health Organization estimates.

A new disease spreads widely in part because of careless public health, Heymann says. He uses hepatitis C as an example.

“Hepatitis C spread all over the world, in large part because of improper sterilization of needles,” Heymann says. “We didn’t find it soon enough, and sterilization was not given enough priority. There was a false confidence that we didn’t have to worry about infectious diseases anymore because we have vaccines and anti-viral drugs. We didn’t identify the problem until 10 years ago, when it had already become more resistant to treatment.”

That’s the terrifying thing about emerging viruses. When new ones first enter the human population, scientists don’t know anything about them. They can spread rapidly and be hard to treat. Scientists don’t know where they came from or how they are spread.

“They are very frightening and very dangerous,” Heymann says.

‘Scared of the unknown’

There is also a narrow window of opportunity for treating and preventing viruses when a new medication or vaccine is developed, because the viruses are constantly adapting and changing.

This can lead to a sense of helplessness, Peters says. “People are scared of the unknown. They don’t think there’s anything they can do about these viruses, and they don’t know what all could be involved. They can have some pretty horrible symptoms,” he says.

The scariest are the viruses that cause hemorrhagic fever. Some strains of these viruses can kill 60 percent of their victims.

In an effort to better track these hemorrhagic fever viruses and other insect-borne diseases, the WHO has set up a “network of networks for global surveillance,” with many labs throughout the world — government, university and military labs, and global public health information networks (with different search components) that provide the agency with information.

When there is an outbreak verification, the list goes out to collaborating partners who help determine where the disease originated, how it’s spread and how it can best be contained, Heymann says.

While their plant and animal hosts are moving about the globe, the viruses are rapidly evolving “new” species.

“We may only have the next decade or two in which to make optimal use of available medicines, control the spread of the most dangerous infectious diseases and reduce the threat of drug resistance. We are literally in a race against time to bring down levels of infectious diseases worldwide, before the diseases wear the drugs down first,” Heymann says.

A virus hunter, Peters says, is a little like the drunk crawling around on the ground looking for his keys. Someone asks where did you last see them? and he says, “Over there by the car.” They ask, “Why are you looking over here?” and he says, “The light’s better.”