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West Nile Virus

Introduction

An outbreak of West Nile Virus in the New York City area in late summer 1999 captured widespread media attention. Images of dead crows and helicopters spraying insecticides provided a dramatic backdrop for stories on the appearance of a mosquito-borne disease never before seen in the Western Hemisphere.

As weather warms and mosquito season gets into high gear, West Nile Virus is likely to make headlines again. This year, the "never-heard-of-it" syndrome is no excuse for uninformed reporting. Media have an opportunity for more deliberate coverage and analysis of this emerging environmental disease.

For now, neither panic in the streets nor blasé inattention and inaction will be the antidote. Of course, scare stories are a big temptation for TV stations during sweeps weeks. And fear of the unknown made the West Nile Virus seem especially scary last year. In fact, however, scientists from the U.S. Geological Survey, U.S. Centers for Disease Control and Prevention and other federal, state, and local agencies actually know a great deal about the virus and what to do about it. Journalists can report the wealth of information that is known, in hopes of encouraging timely and effective public understanding and response.

Why Cover It?

The West Nile Virus can make people sick or kill them. Seven people died in the 1999 Northeast outbreak that severely sickened 62 people. Some 3-15 percent of cases are fatal, although fatalities are likeliest among the elderly and others with weak immune systems.

But if the media approach West Nile solely as a human health story, they may repeat the errors of the past in which too many environmental risks were viewed solely from the perspective of potential cancer-causing impacts, and not from a broader ecological standpoint. The public should understand that impacts of the virus on wildlife can have systemic effects on entire ecosystems.

The virus is of potential news value also simply because it is new to the Western Hemisphere. Just how quickly or widely it could spread is still an unknown. But because it is passed along to humans from mosquitoes that have fed on infected birds such as crows (note: crows do not pass the virus directly to humans) found throughout the United States, outbreaks could occur beyond the mid-Atlantic states, such as New York, New Jersey, and Connecticut which have already been identified with the virus.

Story Ideas

1. What surveillance programs are being conducted in your area to detect West Nile fever in humans, (or for that matter, St. Louis encephalitis, and other "notifiable" diseases)? What are the findings to date? What is the significance of the findings? Check with state and local health agencies and with CDC.

2. Take a look at the role birds will play in detecting the disease, alerting public health officials to hot spots, and helping direct mosquito control operations. What types of birds can be infected by the virus and what effect could it have on migratory bird populations? Will migratory birds spread the disease to other parts of the hemisphere and other species of wildlife?

3. How should people handle dead birds? Who should they call? Can they touch them? What kinds of signs/symptoms should the public be on the lookout for?

4. What populations of birds or domestic animals and mosquitoes in your area could take part in the transmission cycle of West Nile Virus? Who, if anyone, is monitoring those animal populations, and how effectively? Will it spread to warmer climates where it could become established as a year round threat to wildlife, domestic animals, and humans?

5. Does your area have one or more mosquito control and abatement programs, districts, or agencies? How effective are their efforts? What other mosquito-borne diseases affect people or animals in your area? What mosquito-control methods are used and are they preventive or reactive?

6. Is there a truck or aerial insecticide-spraying program in your area? What insecticides are used? What are the benefits and potential adverse effects? How, where, and when are the pesticides applied? What precautions should people take to avoid unnecessary or harmful exposure to pesticides being sprayed? Have government agencies and the media been effective in informing people about those precautions?

7. How can residents protect themselves from mosquitoes and best suppress mosquito breeding near their homes?

The Virus: Its Effects and How It is Transmitted

The West Nile Virus is primarily a disease of birds. It is commonly found in Africa, West Asia, and the Middle East, but has also caused outbreaks in Europe. In humans, it can cause encephalitis, an infection of the brain. West Nile Virus is similar to the virus that causes St. Louis encephalitis, which for years has been found in the United States. West Nile had not been found in the United States before the late summer of 1999.

Most people infected by the West Nile Virus have no symptoms at all, or experience something that feels like flu. Symptoms of "West Nile fever" may include fever, headache, achy muscles, and extreme tiredness, perhaps with skin rash and swollen lymph glands. In a fraction of cases, the fever leads to encephalitis, which is fatal in some cases or may cause neurologic after-effects. There is no vaccine against West Nile, and no known "cure." As with other viral diseases, treatment consists of support until it has run its course. The incubation period -- the time between an infectious bite and the onset of symptoms -- is usually 5-15 days.

Humans get the West Nile Virus largely from the bite of mosquitoes. Although some 150 species of mosquitoes are found in the United States, the primary transmitter of West Nile is Culex pipiens. The female mosquito catches the virus when it bites an infected bird, and can then pass it along if it later bites a human. Humans do not get it from other humans or animals.

The virus can infect many different species of birds and other animals, but crows seem particularly vulnerable, and monitoring programs focus on them. In fact birds were the key to solving the 1999 outbreak. CDC epidemiologists identified the West Nile virus and linked it to the human illness after pathologists found the disease in flamingos, herons, and bald eagles that had been dying at the Bronx Zoo. The virus has been found also in horses and a cat.

The human cases and fatalities in the 1999 outbreak were all in the New York City area, but infected mosquitoes and birds were found also in Connecticut and New Jersey. Last fall, one infected crow was found as far south as Baltimore, Maryland. The fall 1999 outbreak ended when the hard frosts of the oncoming winter ended most mosquito activity. But some infected mosquitoes have survived the winter, and this has prompted public health agencies to continue monitoring mosquitoes and USGS to continue actively monitoring bird populations.

Background and Context

The West Nile Virus and the encephalitis it can cause pose serious public health concerns, but journalists can best serve their audiences by keeping the risks in some perspective.

Possibly the most newsworthy thing about the West Nile Virus is merely that it is new -- not that it is an unusually large "big picture" threat to public health. Other mosquito- or insect-borne viral encephalitis diseases in fact are found regularly in the United States.

A major epidemic of St. Louis encephalitis (223 cases and 11 deaths) occurred in Florida in 1990, and a few dozen non-fatal cases were reported in 1998, the last year for which statistics are available. St. Louis encephalitis is the most common mosquito-borne disease and the leading cause of viral encephalitis in the United States. Since 1964, there have been 4,437 cases -- averaging 193 cases (but ranging from 4 to 1,967) per year. Estimates are that 1 percent of people infected actually get sick, but that 5-15 percent of those who get sick die.

It may be worth portraying last year’s seven deaths from West Nile in the context of other infectious diseases. For example, some 3,000 cases of bacterial meningitis occur every year in the United States, despite the availability of vaccines. Some 10-13 percent of those patients die despite getting antibiotics, and another 10 percent have severe after-effects, including mental retardation. From another perspective, recognize that the seven 1999 deaths from West Nile deaths compares with 16,516 deaths from AIDS in the United States in 1997.

Incidence of the virus in wildlife may be as important an issue as incidence among humans. This is not only because wildlife may be a reservoir of a virus which can potentially threaten humans, but because diseases introduced in wildlife have the potential to impact wildlife populations, in this case bird populations, which in turn could affect local or regional ecosystems.

USGS’s National Wildlife Health Center and other surveillance agencies have found West Nile in at least 18 species of wild birds ranging from pigeons and bluejays to a mallard duck. Continued monitoring will be essential to detecting risks to both humans and wildlife. USGS National Mapping Division is collaborating with state and federal agencies to incorporate the epidemiology information on the outbreak into a geographic information system (GIS) for display and analysis.

Issues

Beyond the TV tabloid-magazine screaming alarms about West Nile, some important public policy issues have gone largely unexamined by the media.

- How are local mosquito-control programs funded, and how well-funded are they? Is this funding a federal, state, or local responsibility?

- Is the cure sometimes worse than the disease, and is prevention an alternative to remedy after-the-fact? Authorities said aerial spraying of the pesticide Malathion in New York during 1999 was safe and justified by disease risks. But some environmentalists questioned the risks of such broad public exposures.

- How many other "emerging diseases" are popping up on the radar screens of health surveillance authorities (or sneaking under the radar, as West Nile almost did)?

- What work is being done on vaccines for insect-borne viral encephalitis diseases? How well funded is it, and what priority is it being given?

- What other exotic species are threatening our landscapes, our waters, and our native plants and wildlife?

- What sort of cooperation exists between the different state and federal agencies working on human, domestic animal, and wildlife health and disease problems?

Key Players

Here are some of the major actors and news sources on West Nile Virus:

- U.S. Centers for Disease Control and Prevention. Federal agency responsible for disease surveillance and epidemiological detective work.

- U.S. Geological Survey and the USGS National Wildlife Health Center. Federal agency responsible for monitoring the viral infection in wildlife and mapping the infection in humans and wildlife.

- U.S. Environmental Protection Agency. Responsible for pesticide safety.

- City, county, and state health departments. Agencies responsible for collecting reports of diseases and passing them along to CDC, and also for preventing and responding to local disease outbreaks.

- Local and state mosquito control and abatement districts or agencies. Responsible for keeping mosquito populations down. - State wildlife agencies. May help monitor health of bird populations.

- Local medical research centers or hospitals. May treat actual cases and have experts to interview.

Sources on the Web ... and Phone Contacts

- U.S. Geological Survey, West Nile Virus Resource Page, http://www.usgs.gov/west_nile_virus.html. Contacts: Linda Glaser at (608) 270-2446, Robert McLean at (608) 270-2401 or Paul Slota (press contact) (608) 270-2420, at the USGS National Wildlife Health Center; or Butch Kinerney, press contact at USGS Headquarters in Reston, VA, (703) 648-4732.

- Centers for Disease Control and Prevention, CDC Answers Your Questions About West Nile Encephalitis, http://www.cdc.gov/ncidod/dvbid/arbor/West_Nile_QA.htm. Contact: CDC, Division of Media Relations in Atlanta, GA, at (404) 639-3286.

- Environmental Protection Agency, Pesticides & Mosquito Control, http://www.epa.gov/pesticides/citizens/mosquitocontrol.htm. Contact: Ellen Kramer, (202) 564-7839. - Sean Ahearn, Ph.D., Hunter College, (212) 772-5327, sca@geo.hunter.cuny.edu.

Reprinted with permission. Published in Environment Writer newsletter May 2000, by the National Safety Council's Environmental Health Center.