<P> Differences in surveillance and reporting between health departments and generally increased surveillance as the disease spread cause some problems in direct comparison of the number of cases and the mortality rate . The reported number of infected in 2009 was 720, but the estimated total number of infected the same year was 54,000 . The true mortality rate is thought to be much lower because most cases are so mild they go undiagnosed . Some estimates put severe cases at only 1% of all cases . It is believed that the elderly or people with weak immune systems are most vulnerable to serious illness or death if bitten by a mosquito infected by West Nile . Most but not all mild cases go undiagnosed . In addition, some more severe but non-neuroinvasive cases are not reported to the CDC . Some mild cases are discovered during blood donation screening . 1,039 West Nile - tainted blood donations were discovered between 2003 and mid-2005. 30 cases of West Nile from blood transfusion were known, the majority from 2002 before blood screening was instituted . In the first ten years since the virus arrived in the U.S., over 1,100 deaths occurred with human cases reported from every U.S. state except Maine, Alaska and Hawaii . (Animal cases have been occasionally found in Maine and in Puerto Rico .) </P> <P> In 2012, there was a widespread outbreak with the highest death toll and second - highest total case numbers . Maine and Puerto Rico reported one case each, the first time the disease was reported in those places . </P> <P> In August 1999, Dr. Deborah Asnis, an infectious disease specialist at Flushing Hospital Medical Center in Queens, noticed two male patients who were suffering from similar, unusual symptoms . The two patients, aged 60 and 75 respectively, were exhibiting sudden paralysis in their in their arms and legs, as well as disorientation and high fevers . Lab testing also showed elevated numbers of white blood cells within the spinal fluid of both males . Neither of the patients were responding to antiviral drugs . Possible early hypothesizes included botulism, viral encephalitis, Guillain--Barré syndrome, or meningitis, but none of these illnesses exactly matched the symptoms . Asnis decided to pursue a more concrete diagnosis by contacting authorities and other colleagues . </P> <P> Dr. Asnis contacted Dr. Marcelle Layton, the New York City Department of Health's chief epidemiologist, on Monday, August 23, 1999, to report her patients' symptoms . Layton advised Asnis to send samples of the patients' blood and spinal fluid to the New York State Department of Health in Albany for further analysis . By Friday, August 27, 1999, just four days after Asnis had contacted Layton, two additional patients had been identified in Queens . The number rose to eight by Sunday, August 29, at Flushing Hospital Medical Center and other hospitals in Queens . All of the early patients resided within a few miles of one another . They were also frequent gardeners in the evenings . </P>

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