More mosquitoes on Long Island: What to know about West Nile virus, eastern equine encephalitis
September is the peak month for mosquitoes and West Nile virus, but they got an early start on Long Island this year.
Health officials reported larger numbers of infected mosquitoes compared with recent years, as well as more human cases of West Nile and biting mosquitoes overall in Suffolk County in July and August, possibly setting the stage for additional cases of disease later this year.
Even more troubling to experts is the growing spread in the Northeast of eastern equine encephalitis, another mosquito-borne disease that can be more deadly. For the first time in five years, an EEE-infected mosquito sample was found in Suffolk County, officials reported Friday.
While there have been no human EEE cases in New York, they have been documented in New Jersey and Massachusetts. A man from New Hampshire died last month after contracting the virus and developing the disease, and concerns about transmission have led some New England towns to recommend 6 p.m. curfews on outdoor activities this month to avoid infected mosquitoes.
For now, the bigger threat in New York is the West Nile virus, especially for people over the age of 50. Dr. Anthony Fauci, former head of the National Institute of Allergy and Infectious Diseases who was a leading public health voice during the COVID-19 pandemic, was recently hospitalized for about a week after contracting West Nile.
"I’ve never been as sick in my life," Fauci said during an interview with Stat in August while he was recovering at home.
New York State Health Commissioner Dr. James McDonald recently reminded people to take precautions against mosquito bites, especially due to the higher number of West Nile-infected mosquitoes reported in traps.
"There are often more infections on Long Island and in the southern Hudson Valley region when compared with other areas of New York State," agency spokeswoman Danielle DeSouza said. "We see cases of West Nile virus in these areas every year, but we are seeing more cases at this time this year than we have over the last few years on average."
The rainy spring on Long Island provided rich breeding grounds for mosquitoes, leading to high populations earlier than usual, said Scott Campbell, chief of the Suffolk County Health Department’s Arthropod-Borne Disease Laboratory.
Additionally, the hot, relatively dry summer led mosquitoes and birds to share limited water sources, Campbell told Newsday in an email.
"This increases the West Nile virus infection rates in the mosquito populations," he said.
The county has collected about 12% more female mosquitoes so far this year, compared with the same time period last year — 133,977 to 120,122. Female mosquitoes bite humans, but male mosquitoes do not.
As of Aug. 31, there were 197 West Nile virus-positive mosquito samples detected in Suffolk County and 56 in Nassau County. For all of 2023, there were 99 in Suffolk and 52 in Nassau, according to a state Health Department report.
More people have been infected with West Nile in Suffolk this year than all of last year, though cases in Nassau are well below last year's total. There were seven people with West Nile in Suffolk and three in Nassau. Last season, there were four cases in Suffolk and 16 in Nassau.
Campbell noted that between 2000 and 2023, Suffolk averaged around six cases. "We are currently at seven with approximately six weeks of mosquito activity remaining," he said.
Nassau County Health Department spokeswoman Alyssa Zohrabian told Newsday officials there have observed "slightly above-average West Nile virus activity in mosquitoes" this summer and a "slight increase" in the mosquito population compared with last year.
Newsday spoke with entomologists and other experts about mosquito-borne viruses and what you can do to protect yourself.
West Nile virus is spread by the bite of an infected mosquito and can cause a range of symptoms, or none at all. About 1 in 5 experience relatively mild illness, with headaches, body aches, vomiting, rash or joint pains. But about 1 in 150 infected people will develop severe disease that impacts the central nervous system, such as swelling of the brain (encephalitis) or meningitis.
The U.S. Centers for Disease Control and Prevention notes that West Nile is the leading cause of mosquito-borne disease in the continental United States. Its first appearance in the nation was in 1999 in Queens. More than 59,000 human cases were reported between 1999 and 2023, according to the CDC, as 27,000 people were hospitalized from the illness and 2,958 died.
In Suffolk, nine people have died of West Nile since it was first detected in 2000.
West Nile virus, eastern equine encephalitis, dengue, malaria and Zika virus are examples of diseases that are spread to people and other animals by the bite of an infected mosquito.
For example, a mosquito may become infected with West Nile after feeding on an infected bird. That mosquito can transmit the virus to a human or a horse. West Nile is generally not passed from person to person except for some rare cases involving blood transfusion and organ transplants.
The warmer weather, which can be influenced by climate change, can hasten the development of mosquitoes and how often they bite, experts said. Mild winters also have extended the active season for mosquitoes.
Between 2000 and 2023, Suffolk identified on average 105 positive West Nile virus mosquito samples. So far this year, they have identified 197, according to Campbell.
Campbell said summer storms can impact the mosquito population in different ways.
"Heavy rain is a double-edged sword," Campbell said. "It can cause mortality in the adult and larval populations, but can provide standing water for surviving females to lay eggs."
Eastern equine encephalitis, a rare but serious disease, is caused by a virus transmitted to people through the bite of an infected mosquito, according to the CDC. About 30% of people who develop severe illness die. Many survivors have long-term neurological damage.
It infects mammals, birds, reptiles and amphibians. According to the state Department of Health, 11 people in New York have been diagnosed with eastern equine encephalitis since 1971, and seven of them died.
"We have had 16 EEE-positive horses in 10 different counties, which is the largest number of horses we have seen in a single year," DeSouza said. "And if horses are infected, it means that mosquitoes capable of biting mammals are infected and can transmit the virus to horses, humans, and others."
No horses on Long Island have tested positive this year.
Researchers are seeing more eastern equine encephalitis-infected mosquitoes across the Northeast, said Laura Harrington, a professor of entomology at Cornell University who studies mosquito interactions with humans and animals. Transmission of the virus is higher than has been in about a decade, she said.
So far, six human cases of eastern equine encephalitis were reported in five states: Vermont, New Jersey, New Hampshire, Massachusetts and Wisconsin. In recent years, the number of cases nationally has ranged from seven in 2023 to five in 2021 and 13 in 2020. The highest number in the last 20 years was 38 human cases in 2019.
"It’s really hard to determine what causes these cycles," Harrington said. "Definitely, environmental conditions are important ... we now understand that there's a lot of movement from southern states to the north with the bird migration, with infected birds bringing the virus back."
Experts suggest people avoid outdoor areas when mosquitoes are biting. If you have to be outside, wear long sleeves and long pants. Use insect repellent registered with the U.S. Environmental Protection Agency and follow label directions carefully. Eliminate standing water on your property, which can serve as mosquito breeding grounds.
September is the peak month for mosquitoes and West Nile virus, but they got an early start on Long Island this year.
Health officials reported larger numbers of infected mosquitoes compared with recent years, as well as more human cases of West Nile and biting mosquitoes overall in Suffolk County in July and August, possibly setting the stage for additional cases of disease later this year.
Even more troubling to experts is the growing spread in the Northeast of eastern equine encephalitis, another mosquito-borne disease that can be more deadly. For the first time in five years, an EEE-infected mosquito sample was found in Suffolk County, officials reported Friday.
While there have been no human EEE cases in New York, they have been documented in New Jersey and Massachusetts. A man from New Hampshire died last month after contracting the virus and developing the disease, and concerns about transmission have led some New England towns to recommend 6 p.m. curfews on outdoor activities this month to avoid infected mosquitoes.
For now, the bigger threat in New York is the West Nile virus, especially for people over the age of 50. Dr. Anthony Fauci, former head of the National Institute of Allergy and Infectious Diseases who was a leading public health voice during the COVID-19 pandemic, was recently hospitalized for about a week after contracting West Nile.
"I’ve never been as sick in my life," Fauci said during an interview with Stat in August while he was recovering at home.
New York State Health Commissioner Dr. James McDonald recently reminded people to take precautions against mosquito bites, especially due to the higher number of West Nile-infected mosquitoes reported in traps.
"There are often more infections on Long Island and in the southern Hudson Valley region when compared with other areas of New York State," agency spokeswoman Danielle DeSouza said. "We see cases of West Nile virus in these areas every year, but we are seeing more cases at this time this year than we have over the last few years on average."
The rainy spring on Long Island provided rich breeding grounds for mosquitoes, leading to high populations earlier than usual, said Scott Campbell, chief of the Suffolk County Health Department’s Arthropod-Borne Disease Laboratory.
Additionally, the hot, relatively dry summer led mosquitoes and birds to share limited water sources, Campbell told Newsday in an email.
"This increases the West Nile virus infection rates in the mosquito populations," he said.
The county has collected about 12% more female mosquitoes so far this year, compared with the same time period last year — 133,977 to 120,122. Female mosquitoes bite humans, but male mosquitoes do not.
As of Aug. 31, there were 197 West Nile virus-positive mosquito samples detected in Suffolk County and 56 in Nassau County. For all of 2023, there were 99 in Suffolk and 52 in Nassau, according to a state Health Department report.
More people have been infected with West Nile in Suffolk this year than all of last year, though cases in Nassau are well below last year's total. There were seven people with West Nile in Suffolk and three in Nassau. Last season, there were four cases in Suffolk and 16 in Nassau.
Campbell noted that between 2000 and 2023, Suffolk averaged around six cases. "We are currently at seven with approximately six weeks of mosquito activity remaining," he said.
Nassau County Health Department spokeswoman Alyssa Zohrabian told Newsday officials there have observed "slightly above-average West Nile virus activity in mosquitoes" this summer and a "slight increase" in the mosquito population compared with last year.
Newsday spoke with entomologists and other experts about mosquito-borne viruses and what you can do to protect yourself.
What is West Nile virus and why's it a concern?
West Nile virus is spread by the bite of an infected mosquito and can cause a range of symptoms, or none at all. About 1 in 5 experience relatively mild illness, with headaches, body aches, vomiting, rash or joint pains. But about 1 in 150 infected people will develop severe disease that impacts the central nervous system, such as swelling of the brain (encephalitis) or meningitis.
The U.S. Centers for Disease Control and Prevention notes that West Nile is the leading cause of mosquito-borne disease in the continental United States. Its first appearance in the nation was in 1999 in Queens. More than 59,000 human cases were reported between 1999 and 2023, according to the CDC, as 27,000 people were hospitalized from the illness and 2,958 died.
In Suffolk, nine people have died of West Nile since it was first detected in 2000.
How are mosquito-borne diseases spread?
West Nile virus, eastern equine encephalitis, dengue, malaria and Zika virus are examples of diseases that are spread to people and other animals by the bite of an infected mosquito.
For example, a mosquito may become infected with West Nile after feeding on an infected bird. That mosquito can transmit the virus to a human or a horse. West Nile is generally not passed from person to person except for some rare cases involving blood transfusion and organ transplants.
Why are there more infected mosquitoes this year?
The warmer weather, which can be influenced by climate change, can hasten the development of mosquitoes and how often they bite, experts said. Mild winters also have extended the active season for mosquitoes.
Between 2000 and 2023, Suffolk identified on average 105 positive West Nile virus mosquito samples. So far this year, they have identified 197, according to Campbell.
Campbell said summer storms can impact the mosquito population in different ways.
"Heavy rain is a double-edged sword," Campbell said. "It can cause mortality in the adult and larval populations, but can provide standing water for surviving females to lay eggs."
What is eastern equine encephalitis, or EEE?
Eastern equine encephalitis, a rare but serious disease, is caused by a virus transmitted to people through the bite of an infected mosquito, according to the CDC. About 30% of people who develop severe illness die. Many survivors have long-term neurological damage.
It infects mammals, birds, reptiles and amphibians. According to the state Department of Health, 11 people in New York have been diagnosed with eastern equine encephalitis since 1971, and seven of them died.
"We have had 16 EEE-positive horses in 10 different counties, which is the largest number of horses we have seen in a single year," DeSouza said. "And if horses are infected, it means that mosquitoes capable of biting mammals are infected and can transmit the virus to horses, humans, and others."
No horses on Long Island have tested positive this year.
Why do there seem to be more cases this year?
Researchers are seeing more eastern equine encephalitis-infected mosquitoes across the Northeast, said Laura Harrington, a professor of entomology at Cornell University who studies mosquito interactions with humans and animals. Transmission of the virus is higher than has been in about a decade, she said.
So far, six human cases of eastern equine encephalitis were reported in five states: Vermont, New Jersey, New Hampshire, Massachusetts and Wisconsin. In recent years, the number of cases nationally has ranged from seven in 2023 to five in 2021 and 13 in 2020. The highest number in the last 20 years was 38 human cases in 2019.
"It’s really hard to determine what causes these cycles," Harrington said. "Definitely, environmental conditions are important ... we now understand that there's a lot of movement from southern states to the north with the bird migration, with infected birds bringing the virus back."
What can I do to protect myself from mosquito bites?
Experts suggest people avoid outdoor areas when mosquitoes are biting. If you have to be outside, wear long sleeves and long pants. Use insect repellent registered with the U.S. Environmental Protection Agency and follow label directions carefully. Eliminate standing water on your property, which can serve as mosquito breeding grounds.
Lisa joined Newsday as a staff writer in 2019. She previously worked at amNewYork, the New York Daily News and the Asbury Park Press covering politics, government and general assignment.
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