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Date: Thu, 24 Oct 2002
Posted by: Dominick.Ninivaggi@co.suffolk.ny.us

Hear, hear. I also think that stating that the risk to any one individual is low is not really meaningful from a public health point of view. If enough people are exposed to a low risk, the absolute number of people impacted can be significant. Would anyone seriously argue that 500+ people with a brain disease in a single Illinois county is not a public health problem? While pesticides carry a risk, is there any data to suggest that mosquito control pesticides have ever made 3000 people sick and killed nearly 200 in a single year, the way WNV has?

Another way to look at this is to look at EEE. EEE is a lot more serious if you get it than WNV. Yet, EEE has never killed anyone in Suffolk County, as far as we know, while we have 7 clinical cases and 2 deaths from WNV this year. Virulence is not the whole story. EEE comes and goes, we know to look for it in the maple swamps, and we can find it in Culiseta melanura in time to intervene. We seem to be stuck with WNV, it occurs in the most densely inhabited parts of our county, and human cases can occur with little warning from surveillance.

-----Original Message-----

From: Richard Lampman [mailto:rlampman@inhs.uiuc.edu]
Sent: Thursday, October 24, 2002 2:01 PM
To: WESTNILEVIRUS-L@cornell.edu
Subject: Re: PRINT MEDIA COVERAGE OF WEST NILE VIRUS-RELATED RISKS

"IS WEST NILE VIRUS BEING OVER-HYPED?"

Considering the relatively low mortality rate in humans (5-10%), WNV might be considered of minor public health importance, but there is ample evidence that this arbovirus may have considerable impact on both human and animal health.

First, the early estimate of severe complications in human cases (about one out of 150 cases) based on a serosurvey in Queens, New York, underestimated the human response in Illinois. The 6% case fatality rate certainly exceeded the less than 1% prediction of severe complications. Furthermore, there is an indication that WNV is causing serious sequelae in some patients, such as flaccid paralysis.

Second, West Nile virus has become a potential human risk beyond the mosquito route. Recent reports suggest that transmission may also occur through blood transfusion, organ transplantation, and via breast milk. The long-term implications of these transmission routes are unknown. A rapid detection technique for WNV in blood is being developed. The impact of WNV on vertebrates appears to broaden as studies continue to learn more about this arbovirus. Some reports even suggest there has been a change in virus virulence. Unfortunately, there is simply too little scientific data at present to answer some important questions about human and animal health. It is only prudent at this point to be cautious addressing issues of risk.

Third, many are suggesting that WNV is going to burn out its reservoir hosts and disappear next year. There is simply no scientific evidence to support this on any short-term scale. WNV remains a problem in Suffolk County, New York. Past evidence suggest antibody rates in avian species vary from year to year and from region to region. How can we predict the future when we don't even know the major reservoir hosts or the geographic variation in transmission dynamics? It is reasonable to assume that eventually an age-stratification of antibody response will occur in humans, but the exact time scale for this to occur needs a lot more data (and what if virulence changes?). Hopefully, there will be several states doing serosurveys this fall and winter.

Fourth, arboviral diseases are generally considered preventable through mosquito management and avoidance of mosquito bites. Therefore, it was entirely appropriate for news media to repeatedly remind the public of checking their immediate surroundings for breeding sites and eliminating them and recommending modification of outdoor behavior and the proper use of repellents. Weren't those the main points of the news reports? Wouldn't it have detracted from the message if each report had added a qualifier that WNV causes less mortality than influenza or slipping on soap in the shower? And, isn't this an unfair comparison anyway?

There should be a public discussion on the impact of mosquito pesticides but keep in mind that this is a controversial and complex issue not easily reduced to a short report because the discussion has to include larvicides and adulticides, target and non-target impacts, proper and improper use, urban vs. natural area use, timing of spraying, etc. If used properly, there appears to be an overwhelming amount of peer-reviewed and governmental data supporting the safety of public health pesticides, especially used at ULV.

Finally, although frequently overlooked, West Nile encephalitis is causing one of the most widespread epizootics in birds and horses in recent US history. The number of horses infected with WNV outnumbers the human cases by at least three-fold (about 11,000 horse cases as of Oct. 19) and some estimate up to 10-fold. Illinois, Indiana, and Ohio are reporting hundreds of sick raptors, most of which are positive for WNV. In 2001, about 5200 dead crows and bluejays were found to have WNV. The mortality rate on other species is unknown. It is likely that 100,000s of birds were exposed to WNV in 2002 and the ecological consequences of such a widespread bird infection (with variable levels of mortality and morbidity) are unknown at this point.

Rich Lampman

PRESS RELEASE: STUDY OF PRINT MEDIA COVERAGE OF WEST NILE VIRUS-RELATED RISKS
Initiative for Vector and Insect Science, Biology Department, Boston College

Communicating information about the relative magnitude of health threats to the public is important because it can assist citizens in investing their time and resources in proportion to the the risks they face. The print news media are important sources of such information. The emergence of West Nile virus (WNV) in the United States in the last three years has been covered extensively in the print media, and has generated considerable anxiety in many citizens.

To examine the extent to which print media provided precise information on the risks of WNV, Drs. John Roche and Marc Muskavitch and colleagues, of the Biology Department at Boston College, conducted a content-analysis study of West Nile virus coverage in major North American newspapers. They looked at the percentage of newspaper articles that reported WNV risk magnitude in terms of numbers affected per size of population potentially affected (i.e., numerator/denominator-level information), what percentage provided risk information that was simply numerical (with no population size context; e.g., "62 people became ill"), and what percentage provided risk information that was simply qualitative (e.g., "West Nile virus is dangerous"). Reporting risk magnitude within the context of numerator/denominator probability is important because without context, citizens can considerably underestimate or overestimate their risk.

Drs. Roche and Muskavitch found that fewer than 10% of the more than 350 newspaper articles surveyed presented contextually precise (i.e., numerator/denominator) information about the human risks of WNV-related illness, and fewer than 10% reported contextually precise information about the risk of WNV-induced human mortality, even though contextually precise information on these parameters was widely available. Information about risks, when presented, was generally presented only at the qualitative level or the numerical level. Drs. Roche and Muskavitch also found that few articles (fewer than 5%) provided comparisons between the health risks of WNV-related illness and the risk of more familiar health threats (e.g., the risk of dying from influenza). Such comparisons can be effective in helping citizens put new risks in probabilistic perspective.

In a related content-analysis study, Drs. Roche and Muskavitch investigated the degree to which articles in major North American newspapers provided information about the health risks of pesticide exposure related to mosquito control. They found that no articles surveyed provided numerator/denominator-level information about the risk of pesticide exposure, and fewer than 3% gave even numerator-level information about pesticide-exposure risks.

The lack of contextually precise information on risks and relative risks could limit individuals' ability to respond proportionally to the threat of WNV. Similarly, it could limit citizens' ability to make informed decisions about whether to support or oppose mosquito control via pesticide spraying. This situation could be addressed, in part, through increased dialogue among journalists, scientists, and public health experts. These studies will be appearing in the journals Science Communication and the Journal of Urban Health.

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