Double Helix | October 7, 2012 at 3:50 pm

Combating West Nile Virus, Effectively

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The West Nile Virus outbreak this year has been one of the worst on record. As of September 25, there have been 3,545 cases, with almost 40 percent of those in Texas. Recently, the Centers for Disease Control and Prevention reported a deceleration in the number of new West Nile Virus cases, which suggests the season may be coming to an end.

Most public health efforts regarding prevention of West Nile Virus during the season involve mosquito surveillance and advising citizens to take precautions like staying indoors or wearing bug spray. However, a number of factors can stymie prolonged protective behavior in the population. Ineffective communication can lead people to downplay the actual threat of the disease, which causes symptoms ranging from fever to encephalitis (swelling of the brain) and even death. Additionally, people may de-emphasize the benefits of protecting oneself, or after the novelty of the threat has faded, normalize and ignore the threat.

It’s clear that hoping for successful communication between officials and citizens is not enough. If global warming is indeed responsible for the severe West Nile season, and unseasonably warm climate patterns persist, the range of West Nile will only increase. Structural solutions like pesticide spraying and larvicide distribution, therefore, should be standardized for all regions at risk.

Many areas already have infrastructure in place for mosquito spraying during outbreaks, but there are few clear guidelines as to when it is appropriate to utilize that infrastructure. The official CDC guidelines for spraying during West Nile Virus outbreaks give no guidelines other than that spraying is recommended when human cases are reported, leaving further decisions to the states. This suggests that public health agencies consider mosquito-borne diseases to be relatively endemic and regional, which has generally been true in the past in cases of Eastern Equine Encephalitis outbreaks.

However, this recent West Nile Virus outbreak has demonstrated the capacity for an epidemic to spread from essentially one state, Texas, to the entire country. The speed with which this epidemic has moved has demonstrated that even though we consider WNV to be an “emerging” infectious disease, it has a capacity to be a serious national public health threat.

In order to have an effective public health response, states must act quickly against threats like disease-carrying mosquitoes. It is therefore discouraging to see that only some states have official policies on mosquito control, that these policies are highly variable, and that even states with policies have trouble mobilizing a response. For instance, Texas, a state with an official mosquito control policy, only began spraying at the end of August 2012, after 586 cases and 21 deaths from WNV had already been reported. If this response speed were for something like a foodborne outbreak, you could guarantee that public officials would be chastised for not taking action sooner to protect the public.

Part of the reason Texas may have been slow to respond is that mosquito spraying wasn’t a part of its routine protocol, having not been used in 43 years before this WNV outbreak. But once carried out, the results of the spraying were breathtaking: areas that were sprayed twice consecutively reported a 93 percent decrease in disease-carrying mosquitoes, while areas that were not sprayed reported an increase. The successes of mosquito spraying are evident; it should now be an imperative to rewrite existing policy in such a way that spraying as a form of outbreak response is just as legitimate and essential as surveillance and public health education.

As new threats to public health change, so must the official response to protect populations. Communicating the nature of the threat to the public, always a balancing act of adequately conveying risk without inciting social panic, may no longer be enough. Ultimately, an epidemic, West Nile or otherwise, is not merely an environmental or an economic concern; it’s a public health issue, which should be combated with substantive action that directly addresses the factors that cause the disease.

 

Photo Credit: Spike Walker, Wellcome Images

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