West Nile virus outbreak

The United States is experiencing its worst seasonal outbreak of the mosquito-borne West Nile virus. A total of 3,545 cases, including 147 deaths, were reported in the United States in 2012, the highest human toll by that point in the calendar since the mosquito-borne disease was first detected in the country in 1999.

This undated photo provided by the Northwest Mosquito Abatement District shows a Culex pipiens, left, the primary mosquito that can transmit West Nile virus to humans, birds and other animals. It is produced from stagnant water. The bite of this mosquito is very gentle and usually unnoticed by people. At right is an Aedes vexans, primarily a nuisance mosquito produced from freshwater. It is a very aggressive biting mosquito but not an important transmitter of disease. (AP Photo/courtesy the Northwestern Mosquito Abatement District)
This undated photo provided by the Northwest Mosquito Abatement District shows a Culex pipiens, left, the primary mosquito that can transmit West Nile virus to humans, birds and other animals. It is produced from stagnant water. The bite of this mosquito is very gentle and usually unnoticed by people. At right is an Aedes vexans, primarily a nuisance mosquito produced from freshwater. It is a very aggressive biting mosquito but not an important transmitter of disease. (AP Photo/courtesy the Northwestern Mosquito Abatement District)
This undated photo provided by the Northwest Mosquito Abatement District shows a Culex pipiens, left, the primary mosquito that can transmit West Nile virus to humans, birds and other animals. It is produced from stagnant water. The bite of this mosquito is very gentle and usually unnoticed by people. At right is an Aedes vexans, primarily a nuisance mosquito produced from freshwater. It is a very aggressive biting mosquito but not an important transmitter of disease. (AP Photo/courtesy the Northwestern Mosquito Abatement District)
In this photo provided by the Northwest Mosquito Abatement District, lab assistant Carter Sharp sorts mosquitoes Thursday, July 26, 2012, in Wheeling, Ill., that were collected from Chicago's northwest suburbs for West Nile virus testing. Illinois already has seen at least two human West Nile virus infections this year, more than a month earlier than usual. The rate of infected mosquitoes in the state is the highest in a decade and higher than in 2002 when 67 people died. Health officials say the hot, dry weather is a factor. (AP Photo/Courtesy the Northwest Mosquito Abatement District, Michael Szyska)
In this photo provided by the Northwest Mosquito Abatement District, lab assistant Carter Sharp sorts mosquitoes Thursday, July 26, 2012, in Wheeling, Ill., that were collected from Chicago's northwest suburbs for West Nile virus testing. Illinois already has seen at least two human West Nile virus infections this year, more than a month earlier than usual. The rate of infected mosquitoes in the state is the highest in a decade and higher than in 2002 when 67 people died. Health officials say the hot, dry weather is a factor. (AP Photo/Courtesy the Northwest Mosquito Abatement District, Michael Szyska)
In this photo provided by the Northwest Mosquito Abatement District, lab assistant Carter Sharp sorts mosquitoes Thursday, July 26, 2012, in Wheeling, Ill., that were collected from Chicago's northwest suburbs for West Nile virus testing. Illinois already has seen at least two human West Nile virus infections this year, more than a month earlier than usual. The rate of infected mosquitoes in the state is the highest in a decade and higher than in 2002 when 67 people died. Health officials say the hot, dry weather is a factor. (AP Photo/Courtesy the Northwest Mosquito Abatement District, Michael Szyska)
Texas health department says at least 10 have died from infections
Dallas in state of emergency over West Nile virus
Texas health department says at least 10 have died from infections
West Nile virus (Flavivirus) was first discovered in Africa and was accidentally introduced to the United States, according to the USDA. The virus is primarily an avian pathogen, transmitted among birds by bird-biting mosquitoes, such as the As
Why Is West Nile Virus So Bad This Year?
West Nile virus (Flavivirus) was first discovered in Africa and was accidentally introduced to the United States, according to the USDA. The virus is primarily an avian pathogen, transmitted among birds by bird-biting mosquitoes, such as the As
Mosquitos are sorted at the Dallas County mosquito lab in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mosquitos are sorted at the Dallas County mosquito lab in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mosquitos are sorted at the Dallas County mosquito lab in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mosquito tech Spencer Lockwood sorts mosquitos at the Dallas County mosquito lab in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mosquito tech Spencer Lockwood sorts mosquitos at the Dallas County mosquito lab in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mosquito tech Spencer Lockwood sorts mosquitos at the Dallas County mosquito lab in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Dead mosquitos are lined up waiting to be sorted at the Dallas County mosquito lab in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Dead mosquitos are lined up waiting to be sorted at the Dallas County mosquito lab in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Dead mosquitos are lined up waiting to be sorted at the Dallas County mosquito lab in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mike Stuart of Dynamic Aviation describes the plane that will be used for aerial spraying and it's difference from crop dusting during a news conference in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mike Stuart of Dynamic Aviation describes the plane that will be used for aerial spraying and it's difference from crop dusting during a news conference in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mike Stuart of Dynamic Aviation describes the plane that will be used for aerial spraying and it's difference from crop dusting during a news conference in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mike Stuart of Dynamic Aviation describes a plane that will be used for aerial spraying to the media in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mike Stuart of Dynamic Aviation describes a plane that will be used for aerial spraying to the media in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)
Mike Stuart of Dynamic Aviation describes a plane that will be used for aerial spraying to the media in Dallas, Thursday, Aug. 16, 2012. The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths. But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill. (AP Photo/LM Otero)

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