Arizona health officials are warning that hantavirus, a virus transmitted to humans by rodents, is causing a surge in a potentially deadly lung 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, typically report one to four cases per year. Two people in California have been infected with hantavirus this year.
There is no specific treatment or vaccine that provides protection against the infection.
According to the Centers for Disease Control and Prevention, Arizona has one of the highest reported rates of hantavirus infections in the U.S.
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 cause of serious, even fatal, respiratory infections,” said Dr. Aaron Glatt, chief of infectious diseases at Mount Sinai South Nassau Hospital on Long Island, New York.
“It’s transmitted by several rodents, particularly the deer mouse, and can cause mild disease, but it does cause fatal disease in a significant percentage of people who get this disease,” he said.
Additionally, San Diego County is reporting increased hantavirus rodent activity 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 any higher than normal this year in the U.S., according to the California Department of Public Health.
Why are cases increasing in Arizona?
The CDC has reported 850 cases between 1993 and 2021, which amounts to about 30 cases per year.
Trish Lees, public information officer with Coconino County Health and Human Services, said the increase in cases in Arizona may be due to changes in the rodent population, which can fluctuate seasonally and annually.
While cases can occur at any time, they are more common in the summer when rodents are more active and people are more likely to come into contact with rodents because they spend more time outdoors and enter enclosed spaces such as a barn or shed, Lees said.
“Weather can affect hantavirus prevalence in complex ways. For example, heavy spring rains can increase food sources for deer mice, resulting in increased rodent populations. However, no link has been established between extreme heat and increased hantavirus activity,” according to the California Department of Public Health.
Experts suspect that climate change, such as the extreme heat waves plaguing the country, is partly to blame.
Dr. Camilo Mora, a professor in the department of geography and environment at the University of Hawaii at Manoa, says humans aren’t the only ones seeking shelter when it gets really wet or hot outside. Other species also seek relief from the unfriendly weather — particularly mammals that carry pathogens.
His previous research found that more than half of the infectious diseases that affect humans could be exacerbated by climate change.
“Many disease-carrying species are moving with climate change. Although it is difficult to conclude the role of climate change in a specific case, climate change has all the characteristics to cause outbreaks of vector-borne diseases,” 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 an increase in the rodent population where hantavirus is circulating will inevitably increase the risk of human exposure.
The warm weather can also make the illnesses worse after people become infected through dehydration or other factors, Glatt said.
According to the CDC, about 94% of hantavirus infections occur west of the Mississippi River.
Symptoms of hantavirus
Particles containing hantavirus become airborne when deer mouse urine, saliva, or feces are agitated, leading to hantavirus pulmonary syndrome (HPS).
The syndrome was first recognized in 1993 after a mysterious illness infected members of a Navajo tribe living on the border of New Mexico and Arizona, according to an earlier report. About 80 percent of the people infected died at the time.
Symptoms may appear one to eight weeks after exposure to an infected rodent.
The disease progresses in two stages.
In the early stages of the disease, people may suddenly begin to complain of nonspecific symptoms:
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Fever.
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Fatigue.
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Muscle pain, 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 and infect the lungs, causing fluid to “leak” through blood vessels. This can cause fluid to back up into the airways, causing shortness of breath, chest tightness and coughing, according to the American Lung Association.
About 38% of people who develop lung symptoms may die from the disease.
How do you prevent hantavirus?
“The best way to prevent infection with this disease is to carefully disinfect the rodents and clean up all their droppings and to avoid coming into contact with them,” Glatt said.
The Wyoming Department of Health is warning to be cautious during spring cleaning. The department has not seen any unusual activity among state residents so far this year, a spokesperson confirmed.
Experts say the risk may be greater when opening or cleaning out cabins, sheds, barns or storage areas in rural areas that are closed for the winter and where deer mice have entered.
In 2012, at least 10 people were sickened and three died during an outbreak of hantavirus among visitors staying in tents in Yosemite National Park.
When entering a space that has been closed and unoccupied for a long time, be sure to properly ventilate the area for 30 minutes, warns the Wyoming Department of Health.
If the area is very dirty or infested with mice, take extra care by wearing gloves, shoe covers, overalls, and an N95 mask before cleaning.
This article was originally published on NBCNews.com