Arizona public health officials are warning that hantavirus, a virus that spreads from rodents to humans, is causing a rise in a potentially deadly pulmonary syndrome. There have been seven confirmed cases and three deaths in the past six months, according to a recent health alert.
Most cases of hantavirus are reported in the Western and Southwestern United States. Most states, including California, report one to four cases per year. Two people have contracted hantavirus in California this year.
There is no specific treatment or vaccine that protects against infection.
Arizona is one of the states with the highest number of hantavirus infections reported in the United States, according to the U.S. Centers for Disease Control and Prevention.
According to the Arizona Department of Health Services, there were 11 cases of hantavirus in Arizona between 2016 and 2022: four in 2016, two in 2017, four in 2020 and one in 2022.
“Hantavirus is a rare but important disease that causes serious, even fatal, respiratory tract infections,” said Dr. Aaron Glatt, chief of infectious diseases at Mount Sinai South Nassau Hospital on Long Island, New York.
“It is transmitted through various rodents, particularly the deer mouse, and can cause mild disease, but in a significant percentage of people who contract it, it causes fatal disease,” he said.
Additionally, San Diego County is reporting higher activity in hantavirus-infected rodents this year, with 17 cases of western harvest mice infected with hantavirus. In general, hantavirus activity can fluctuate from year to year and does not appear to be more than normal in the U.S. this year, the California Department of Public Health said.
Why are cases increasing in Arizona?
The CDC reported 850 cases from 1993 to 2021, which works out to about 30 cases per year.
Trish Lees, public information officer for Coconino County Health and Human Services, said the increase in cases in Arizona may be due to changes in rodent populations, which can fluctuate seasonally and annually.
Lees said cases can occur at any time, but are more common in the summer months because rodent activity increases and people come into contact with rodents more often because rodents are outdoors more and enter enclosed spaces such as barns or sheds.
“Weather can influence hantavirus emergence in complex ways; for example, heavy spring rains can increase food resources for deer mice, leading to increased rodent populations; however, no link between extreme temperatures and increased hantavirus activity has been demonstrated,” the California Department of Public Health said.
Experts believe that climate change, such as the extreme heat waves that have affected the country, may be responsible for this situation.
Humans aren’t the only ones seeking shelter when it’s really wet or hot outside, says Dr. Camilo Mora, a professor in the department of geography and environment at the University of Hawaii at Mānoa. Other species, especially pathogen-carrying mammals, also seek respite from the weather.
His previous research had found that more than half of infectious diseases affecting humans could become worse due to climate change.
“Many disease-carrying species move with climate change. So while it’s difficult to determine the role of climate change for a specific case, climate change has all the hallmarks of causing vector-borne disease outbreaks,” he said.
Dr. Scott Roberts, associate medical director of infection prevention at the Yale School of Medicine in New Haven, Connecticut, added that fluctuating environmental conditions can lead to changes in animal populations, so increases in rodent populations in places where hantavirus is circulating would inevitably increase the risk of human exposure to the virus.
Warm weather may have worsened the illnesses after people became infected due to dehydration or other factors, Glatt said.
According to the CDC, about 94% of hantavirus infections occur west of the Mississippi River.
Symptoms of Hantavirus
When deer mouse urine, saliva or feces are mixed, particles containing hantavirus become airborne and cause hantavirus pulmonary syndrome (HPS).
The syndrome was first recognized in 1993 after a mysterious illness affected members of a Navajo tribe living on the border of New Mexico and Arizona. At the time, about 80% of people infected died, according to a previous report.
Symptoms may appear one to eight weeks after exposure to an infected rodent.
The disease has two stages.
In the early stages of the disease, people may suddenly begin to complain of nonspecific symptoms:
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Fire.
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Burnout.
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Muscle aches – especially in the thighs, back and shoulders.
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Nausea, vomiting and abdominal pain.
If left untreated, the disease can become more severe, infecting the lungs and causing fluid to “leak” from the blood vessels, which can cause fluid to build up in the airways and lead to shortness of breath, chest tightness and coughing, according to the American Lung Association.
Approximately 38% of people with pulmonary symptoms die from the disease.
How to prevent hantavirus?
“The best way to prevent transmission of this disease is to carefully disinfect and clean rodent waste and avoid contact with it,” Glatt said.
The Wyoming Department of Health is warning to be careful during spring cleaning. Its public information officer confirmed that the department has not seen any unusual activity among residents in the state so far this year.
Experts say the risk may increase when opening or cleaning sheds, barns or storage buildings in rural areas that have been closed for winter and where deer mice have entered.
In 2012, at least 10 people became ill and three died in a hantavirus outbreak among visitors staying overnight in tents in Yosemite National Park.
The Wyoming Department of Health warns that when you enter a space that has been closed and vacant for a long time, be sure to ventilate the area for 30 minutes.
If the area is very dirty or infested with mice, take extra care by wearing gloves, shoe covers, coveralls, and N95 masks before cleaning.
This article was originally published on NBCNews.com