Hantavirus outbreaks rare, but not unheard of in U.S.
Last month, the world’s attention was gripped by an outbreak of the contagious “Andes strain” of hantavirus aboard the M/V Hondius cruise ship.
According to the most recent reports from the World Health Organization, 13 positive infections and three deaths have been reported so far, all suffered by either passengers or crew members of the ship.
Although experts state it is extremely unlikely for the outbreak to spread far beyond the cruise ship, other strains of hantavirus may be hiding in plain sight in the United States — even in benign places such as the garage.
As of 2023, according to the most recent statistics from the Centers for Disease Control and Prevention, there have been 890 reported cases of hantavirus in the United States since records began in 1993. Of these, the vast majority are in the southwest part of the country. New Mexico has the most cases with 129, followed by Colorado with 121.
Pennsylvania has reported only nine hantavirus cases in a 30-year span, with the most recent occurring in late 2022.
In 2023, when the most recent hantavirus data was recorded by the CDC, 26 individuals across the country tested positive. All but one of these cases occurred west of the Mississippi River, with the lone exception occurring in Louisiana. Of those, 19 survived and seven died.
“Approximately 20 to 30 hantavirus cases occur in the United States every year,” said Dr. Amesh Adalja, senior scholar from the Johns Hopkins Center for Health Security. “These are not related to mass outbreaks, but usually related to individual cases.”
According to Dr. James Como, infectious disease specialist for Allegheny Health Network, the hantavirus strain commonly seen in the United States is the Sin Nombre strain, which is distinct from the Andes strain that ravaged the cruise ship. The Andes strain, on the other hand, is local to Argentina and Chile.
The Hondius cruise ship departed from the Argentine island of Ushuaia in April.
“In North America, cases of hantavirus are attributed to the Sin Nombre Hantavirus,” Como said. “The Andes Hantavirus has not been previously reported in North America. It is primarily found in South America.”
A notable outbreak of the Sin Nombre strain occurred in 1993 — primarily in New Mexico, Colorado and Arizona — leading to 48 confirmed cases and 27 deaths. However, unlike the Andes virus, the Sin Nombre strain cannot spread by human-to-human contact.
“To date, the Andes Hantavirus is the only known hantavirus that has demonstrated human-to-human transmission, though this occurs very inefficiently,” Como said.
While no samples of the Andes virus itself are currently known to exist in North America, there has been at least one confirmed case of the Andes virus on American soil. In January 2018, a woman admitted to a Delaware hospital tested positive for the Andes strain shortly after returning from a two-week trip to Argentina and Chile — where the Andes strain is typically found. After an extensive round of contact tracing, no further positive cases were identified.
Although there are key differences between both strains of hantavirus, the main vector for human infection is the same for both Andes and Sin Nombre — rodent droppings.
“All types of hantavirus are acquired through inhaling aerosolized rodent excreta: saliva, feces and urine,” Como said.
Although hantavirus is uncommon in the United States, it is also uncommonly deadly.
“Mortality rates can reach up to 50%,” Adalja said. “It is a very serious infection.”
Como said that while hantavirus is more commonly found in the southwestern part of the country, infections can theoretically occur anywhere in the U.S.
“The primary hosts for the Sin Nombre virus in North America are rodents, particularly deer mice,” Como said. “Consequently, any area where rodents are present carries a potential risk for acquiring hantavirus infection. While a majority of hantavirus cases are reported in the southwestern U.S., infection can potentially be acquired in any state.”
One common household activity that could possibly trigger an infection, according to both Como and Adalja, is household cleaning in an area overtaken by rodents carrying the virus.
“The activity that likely would expose an individual to the virus would be cleaning out a dwelling that rodents reside in,” Adalja said. “This could be an attic, a shed, a garage or a basement. What might occur with using a broom, for example — aerosolization of rodent droppings occurs and are then inhaled.”
“High-risk activities include changing pet rodent bedding and cleaning out spaces where rodents have been present, such as sweeping a garage or cabin containing rodent droppings,” Como said.
Although there have been only nine known hantavirus cases in Pennsylvania since 1993, there are other diseases that could be spread by rodent droppings, including lymphocytic choriomeningitis and the blood infection leptospirosis.
For those looking to perform spring cleaning who don’t want to take any chances, Como has some suggestions.
“Wearing a surgical mask and eye protection is recommended to minimize the risk of infection,” Como said.
