![West Nile virus map United States 2012 outbreak](https://upload.wikimedia.org/wikipedia/commons/2/26/West_Nile_virus_map_United_States_2012_outbreak.png)
The
West Nile virus
West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family '' Flaviviridae'', from the genus '' Flavivirus'', which also contains the Zika virus, dengue virus, and yellow fever virus. The v ...
quickly spread across the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
after the first reported cases in
Queens, New York
Queens is a borough of New York City, coextensive with Queens County, in the U.S. state of New York. Located on Long Island, it is the largest New York City borough by area. It is bordered by the borough of Brooklyn at the western tip of Long ...
in 1999. The virus is believed to have entered in an infected bird or mosquito, although there is no clear evidence. The disease spread quickly through infected birds.
Mosquito
Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...
es spread the disease to mammals. It was mainly noted in horses but also appeared in a number of other species. The first human cases usually followed within three months of the first appearance of infected birds in the area except where cold weather interrupted the mosquito
vectors. Since the virus has become widely established in the U.S., an average of 130 deaths a year occurred.
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 .
["West Nile Virus Activity – United States, 2009"]
(MMWR 59(25), July 2, 2010) 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 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
Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and ...
,
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S. ...
and
Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...
. (Animal cases have been occasionally found in Maine and in
Puerto Rico
Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and unincorporated ...
.) 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.
Discovery in the United States
In August 1999, the New York State Department of Environmental Conservation (NYSDEC) began receiving reports of large die-offs of crows in parks across New York City. On August 9th, dead wild crows were discovered outside both the Queens Zoo and the Bronx Zoo, prompting head pathologist Dr. Tracey McNamara to begin investigating what was going on.
At the same time, Dr.
Deborah Asnis
Deborah Susan Asnis (July 17, 1956 – September 12, 2015) was an American infectious disease specialist and H.I.V. clinical researcher, who is credited with reporting the first human cases of West Nile virus in the United States.
In August 1999 ...
, an infectious disease specialist at
Flushing Hospital Medical Center
Flushing Hospital Medical Center (also known as Flushing Hospital) is one of the oldest hospitals in New York City. It survived a 1999 bankruptcy and subsequently affiliated first with the New York Presbyterian Hospital and then with the MediSys ...
in
Queens
Queens is a borough of New York City, coextensive with Queens County, in the U.S. state of New York. Located on Long Island, it is the largest New York City borough by area. It is bordered by the borough of Brooklyn at the western tip of Long ...
, 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 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
Botulism is a rare and potentially fatal illness caused by a toxin produced by the bacterium ''Clostridium botulinum''. The disease begins with weakness, blurred vision, feeling tired, and trouble speaking. This may then be followed by weakne ...
, viral encephalitis
Viral encephalitis is inflammation of the brain parenchyma, called encephalitis, by a virus. The different forms of viral encephalitis are called viral encephalitides. It is the most common type of encephalitis and often occurs with viral meningiti ...
, Guillain–Barré syndrome
Guillain–Barré syndrome (GBS) is a rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation or pain oft ...
, 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.][
Dr. Asnis contacted Dr. ]Marcelle Layton Marcelle may refer to:
*Marcelle, a French feminine version of Marcel
*1300 Marcelle (1934 CL), a main-belt asteroid
*Groupe Marcelle, a Canadian cosmetics company
See also
* Marcel (disambiguation)
* Marcell (disambiguation)
Marcell may refer t ...
, the New York City Department of Health
The New York City Department of Health and Mental Hygiene is the department of the government of New York City responsible for public health along with issuing birth certificates, dog licenses, and conducting restaurant inspection and enforcem ...
's chief epidemiologist
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population.
It is a cornerstone of public health, and shapes policy decisions and evidenc ...
, 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
The New York State Department of Health (NYSDOH) is the department of the New York state government responsible for public health. It is headed by Health Commissioner Mary T. Bassett, who was appointed by Governor Hochul and confirmed by the S ...
in Albany for further analysis.[ Around the same time, Dr. McNamara identified a potential viral encephalitis in brain tissue from the dead crows and sent samples off for further testing.] Meanwhile, by Friday, August 27, 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.][
The ]Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
(C.D.C.) initially identified the mystery illness as St. Louis encephalitis on September 3, 1999.[ The city of New York began widespread spraying for mosquitos later that same day.][ However, laboratory testing continued to determine a definitive cause of the symptoms.
On September 9th, Dr. McNamara contacted the C.D.C. with concerns that the epidemiologic pattern of this outbreak were not consistent with St. Louis encephalitis, which does not cause bird die-offs. Additionally, she reported that other known avian viral diseases would have resulted in the deaths of other bird species in the zoos (avian influenza and Newcastle disease would have killed chickens in the petting zoo and eastern equine encephalitis would have killed emus on exhibit). Since only corvids appeared to be dying, she suggested the possibility of a novel pathogen. The C.D.C. disagreed that the epidemiologic pattern was inconsistent and declined to test tissue samples from animal species. Instead, Dr. McNamara sent tissue samples to the ]National Veterinary Services Laboratory The National Veterinary Services Laboratories (NVSL) provides laboratory services for the US Department of Agriculture's Animal and Plant Health Inspection Service (APHIS). It operates from Ames, Iowa and Plum Island Animal Disease Center at Plum Is ...
. On September 11th, they reported that the samples she submitted were positive for a flavivirus
''Flavivirus'' is a genus of positive-strand RNA viruses in the family ''Flaviviridae''. The genus includes the West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, Zika virus and several other viruses which may cau ...
, marking the first time a virus in this genus was implicated in an animal disease.
The U.S. federal government eventually revised its diagnosis from St. Louis encephalitis to West Nile virus
West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family '' Flaviviridae'', from the genus '' Flavivirus'', which also contains the Zika virus, dengue virus, and yellow fever virus. The v ...
on September 27, 1999, based on research by Dr. Duane J. Gubler, a C.D.C. expert on arborviruses
Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo''rne ''virus'') is sometimes used to more spe ...
, and their own testing on samples submitted by Dr. McNamara.
Both Dr. McNamara and Dr. Asnis have been credited by health experts with the early identification of West Nile virus in the United States. Their actions likely prevented a more widespread outbreak. In their 2003 book, ''The New Killer Diseases: How the Alarming Evolution of Germs Threatens Us All'', authors Elinor Levy and Mark Fischetti praised Dr. Asnis' response to the symptoms, writing that, "Asnis did something other doctors might not have bothered to do." They elaborated that, "One of the worst problems with our disease-detection system is that many doctors never report cases of strange symptoms, either because they are unsure of the disease they are facing, they're ignorant of the reporting requirement, or they simply never get around to it. Deborah Asnis was highly conscientious."
Recent cases
During the years between 1999 and 2010, an estimate of 3 million people have been infected in the United States. Highest incidence rates are observed in states of the central great plains, with South Dakota
South Dakota (; Sioux: , ) is a U.S. state in the North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota and Dakota Sioux Native American tribes, who comprise a large porti ...
, Wyoming
Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the s ...
and North Dakota
North Dakota () is a U.S. state in the Upper Midwest, named after the indigenous Dakota Sioux. North Dakota is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north and by the U.S. states of Minnesota to the east, So ...
leading in incidence.
During the 2012 West Nile virus outbreak in Texas
Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
, 1,868 cases were reported. Male patients, persons >65 years of age, and minorities were at highest risk for neuroinvasive disease. At total of 1,868 cases including 844 (45%) WNND (West Nile neuroinvasive disease) cases and 89 deaths (case-fatality rate 5%). Dates of onset ranged from May 1, 2012, through December 6, 2012. The outbreak peaked during week 33 (mid-August) with 225 reported cases, which is historically the same peak for all reported WNV cases in Texas during 2002–2011. The median time from date of symptom onset to date of official report to TxDSHS was 27 days (range 6–274 days). Of the 254 counties in Texas, 135 (53%) reported a WNV case. The overall incidence rate for the state was 7.8 cases per 100,000 population. Almost half of the cases were reported from the northeastern quadrant of the state, including the Dallas/Fort Worth metroplex (902 8%cases): Dallas (396 1%, Tarrant (259 4%, Collin (64 %, and Denton (183 0% counties. These 4 counties had a combined incidence rate of 16 cases per 100,000 population.[ ]
Cases
Sources
Final Cumulative Maps & Data for 1999–2018
an
Centers for Disease Control and Prevention
*2019 also had 104 presumptive cases observed in blood donors
** as of December 15, 2020, also 127 presumptive cases observed in blood donors
Maps of progression
The following maps show the progress of human cases of West Nile across the United States. States are colored according to the percentage of all U.S. West Nile cases they represented in that year. Zero percent (no cases) is colored white; less than 1% is blue; between 1% and 5% is green; between 5% and 10% is yellow, and greater than 10% of cases in a year is red.
Image:1999_west_nile_map.png, 1999
Image:2000_west_nile_map.png, 2000
Image:2001_west_nile_map.png, 2001
Image:2002_west_nile_map.png, 2002
Image:2003_west_nile_map.png, 2003
Image:2004 november west nile map.png, 2004
Image:2005_west_nile_map.png, 2005
Counties of reported cases by year
File:West nile virus cases US 2002.jpg, 2001
File:West Nile virus cases in United States map- May 2003.gif, 2002
File:West Nile virus cases in United States map- 2004.gif, 2003
File:West nile virus case in United States 2006.png, 2006
File:West nile virus case in United States 2007.png, 2007
File:West nile virus case in United States 2008.png, 2008
File:West nile virus cases in United States 2009.png, 2009
File:West nile virus cases in United States 2010.png, 2010
File:West nile virus cases in United States 2011.png, 2011
File:West Nile virus map United States 2012 outbreak.png, 2012
File:West Nile virus cases in United States 2013.png, 2013
File:West Nile virus cases in United States 2014.png, 2014
File:West Nile virus cases in United States 2015.png, 2015
File:West Nile virus cases in United States 2016.png, 2016
References
West Nile Cases Drop as Immunities Emerge, Experts Say
CDC Information Page For Current Cases and Deaths For West Nile Virus
{{DEFAULTSORT:Progress Of The West Nile Virus In The United States
History of science and technology in the United States
Diseases and disorders in the United States
Flaviviruses