Fourteen years after it was first detected in New York, the burden of the West Nile virus continues to have an effect on both our health and our wallets. A study out of the Centers for Disease Control and Prevention (CDC) revealed that the West Nile virus has cost the United States $778 million in health care expenditures since its inception back in the summer of 1999.

"We believe that previous costs associated with West Nile virus disease have been underestimated because they've predominantly focused on the costs of the initial illness," Dr. J. Erin Staples, medical epidemiologist at CDC in Fort Collins, Colo., said in a statement. "Many hospitalized patients will incur additional medical and indirect costs, and these need to be figured into the burden of WNV disease. Only with accurate figures can public health, academic, and industry officials determine the cost effectiveness of local mosquito control measures or of developing new drugs and vaccines."

According to the CDC, between 1999 and 2012, 37,088 people contracted the West Nile virus, in almost all cases, from a mosquito bite. Prior to 1999, the virus was not detected outside of the Eastern Hemisphere. However, it quickly made its way across the U.S. and Canada less than five years after it was introduced. Researchers recruited 80 patients from a Colorado outbreak back in 2003 and calculated the costs of medical care and missed work up to five years after becoming infected. Each year across the U.S. the total cost of the West Nile virus on health care expenditures is upward of $56 million.

Staples and his colleagues say this is the first time research has focused on the costs of four specific “clinical syndromes” including fever, meningitis, encephalitis, and acute flaccid paralysis. Out of all 37,088 patients observed between 1999 and 2012, 18,000 patients were hospitalized, 16,000 developed a neurological disorder, and 1,500 passed away. People over the age of 50 are at a higher risk of being infected by the West Nile virus.

"We broke down costs by clinical syndrome and were surprised by what we found. While patients with meningitis had shorter hospital stays than others with neurological syndromes, they were also younger and more likely to miss work, which translated to a higher economic cost in lost productivity," Staples explained. "Encephalitis patients tended to be older, with many of them retired, so the cost associated with lost productivity was lower."

One out of every five people infected by West Nile will develop a fever or other minor symptoms such as a headache or joint pain. Unfortunately, another one out of 150 patients will develop a serious nervous system illness like meningitis, inflammation of the spinal cord, or encephalitis, inflammation of the brain. Hospitalizations due to partial- or whole- body paralysis, also known as acute flaccid paralysis, cost patients the most at an estimated $25,000 initially and $22,000 long-term.

The average age of each patient in this study was estimated at 55 years and the number of days each hospitalized patient sat out from school or work came to 42 days. Patients and the national cost for West Nile treatment were calculated using the CDC ArboNET surveillance system. The CDC ArboNET tracks all incidences of arthropod-borne viruses (arboviruses), meaning an illness caused by an insect such as a mosquito or tick.

"Understanding the economic impact of disease is an increasingly important data point for the public health community and policy makers," said Dr. Alan J. Magill, president of the American Society of Tropical Medicine and Hygiene. "As we all strive for the most efficient and effective use of scarce resources, studies like this offer decision makers facts that will help them make sound funding and policy decisions."