# 8288
In 1999 the West Nile Virus (WNV) - which is enzootic throughout much of Africa, parts of Europe, Asia and Australia -suddenly, and quite unexpectedly, appeared in New York City. Over the next few years it spread rapidly across the United States.
From the USGS Factsheet on West Nile Virus
In 2002, however, the virus really exploded across the nation’s landscape.
Today, WNV is routinely detected across much of the lower 48 and into Canada, and while the impact varies from year to year (2012 was much more severe than 2013), it is responsible for hundreds of thousands of human infections annually.
Most people infected with WNV experience only mild, or sub-clinical symptoms, but very small percentage develop WNV neuroinvasive disease (WNND), a form of encephalitis. For every serious presentation, there are probably 100 mild, or asymptomatic cases.
Yesterday researchers with the Arboviral Diseases Branch, Centers for Disease Control and Prevention, published the first estimate of the economic impact of this recently introduced mosquito-borne diseases in the United States, and found the virus has likely cost the nation nearly 800 million dollars.
Their estimates come from tracking the medical and lost-productivity costs of 38 WNV cases from Colorado, and extrapolating their costs across the larger case count reported in the United States. They write:
Less than 1% of infected persons develop neuroinvasive disease, which typically manifests as encephalitis, meningitis, or acute flaccid paralysis (AFP). 5 Most patients with WNV meningitis or non-neuroinvasive disease recover completely, but fatigue and malaise can linger for weeks or months.6–8 Patients who recover from WNV encephalitis or AFP often have residual neurologic deficits. 9 Among patients with neuroinvasive disease, the overall case-fatality ratio is 10%, but it is notably higher for patients with WNV encephalitis and AFP.1
From 1999 to 2012, over 36,000 cases and 1,500 deaths caused by WNV disease were reported to the Centers for Disease Control and Prevention (CDC).1,10–12
The study, which appears in the American Journal of Tropical Medicine & Hygiene, may be read at the link below:
Initial and Long-Term Costs of Patients Hospitalized with West Nile Virus Disease
J. Erin Staples*, Manjunath Shankar, James J. Sejvar, Martin I. Meltzer and Marc Fischer
Abstract
There are no published data on the economic burden for specific West Nile virus (WNV) clinical syndromes (i.e., fever, meningitis, encephalitis, and acute flaccid paralysis [AFP]). We estimated initial hospital and lost-productivity costs from 80 patients hospitalized with WNV disease in Colorado during 2003; 38 of these patients were followed for 5 years to determine long-term medical and lost-productivity costs. Initial costs were highest for patients with AFP (median $25,117; range $5,385–$283,381) and encephalitis (median $20,105; range $3,965–$324,167). Long-term costs were highest for patients with AFP (median $22,628; range $624–$439,945) and meningitis (median $10,556; range $0–$260,748).
Extrapolating from this small cohort to national surveillance data, we estimated the total cumulative costs of reported WNV hospitalized cases from 1999 to 2012 to be $778 million (95% confidence interval $673 million–$1.01 billion). These estimates can be used in assessing the cost-effectiveness of interventions to prevent WNV disease.
The authors grant that this study has a number of limitations, including potential recall bias by the patients, differences in medical costs and procedures around the nation, and a small and non-random cohort of cases. They believe their estimate of costs to be conservative, however, as it did not attempt to estimate costs incurred by non-hospitalized cases, or un-reported disease.
The rapid spread of WNV across North America is considered by many as a warning of what could happen in the future with other mosquito-borne illnesses that are spreading around the globe.
Two in particular – Dengue and Chikungunya (CHKV) – are viewed as imminent threats.
In December, in response to the first Chikungunya outbreak in the New World, we saw a CDC HAN Advisory On Recognizing & Treating Chikungunya Infection, and in 2012 the CDC, along with PAHO, produced a document Preparedness and Response for Chikungunya Virus Introduction in the Americas in anticipation of its arrival.
Last November, in Locally Acquired Dengue In New York City, we saw yet another (still rare) example of local transmission of Dengue in the United States, but with reports from both Texas and Florida increasing each year (see Florida: Dengue Forces Suspension Of Blood Donations In Two Counties) concerns are this will only become more common as time goes by.
In 2009 the Natural Resources Defense Council (NRDC) released a report outlining the risks that Dengue could re-establish itself in North America, that included this map showing the areas of the United States that are vulnerable to the introduction of Dengue.
Northern climes are far less likely to see dengue take hold than say, Florida or Southern Texas. Still, in the 18th and 19th century, both Malaria and Yellow Fever were endemic up and down the mid-Atlantic coast.
It’s a not-so-subtle reminder that the barriers we erect against infectious diseases – like mosquito control programs, vaccinations, and public health departments – are as tenuous as they are vital, and can fail us if we do not maintain and support them.
Of course the true burden of these diseases in measured in lives and health lost to or diminished by infection, and is not something we can readily put a dollar sign on.
But for the purposes of allocating funds to fight these diseases, develop vaccines and/or treatments, and prevent future entry of new viruses, having an idea of the economic burden of the disease can greatly assist in making policy decisions.
