The move comes as the World Health Organization works to contain the spread of a hantavirus outbreak aboard the MV Hondius cruise ship.
Five states, including California, are monitoring passengers who recently returned from the ship.
The California Department of Public Health is working with local health jurisdictions to monitor returning travelers. In Central California, agencies such as the Fresno Department of Public Health say they are coordinating with state leaders as the situation continues to evolve.
Kings and Madera Public health departments also confirmed they are watching developments closely.
Health officials say the outbreak is believed to come from the rare Andes strain of the virus. The World Health Organization is monitoring passengers for symptoms and potential exposure.
"Looking at what type of exposure did they have, are they developing any symptoms, if anyone is developing symptoms, to be isolated immediately, testing to take place," said Maria Van Kerkhove, director of epidemic and pandemic preparedness and prevention at WHO.
State health leaders said there is no information that California residents are sick or infected.
Hantavirus is typically spread through rodents, such as deer mice. However, experts say the Andes strain has shown evidence of person-to-person transmission.
"Although not common, there is evidence of person-to-person transmission of that particular species of hantavirus," said Daniel Bausch of the Global Health Centre at the Geneva Graduate Institute.
Dr. Abraar Karan is an infectious disease specialist at Stanford University.
"It's a known virus. We know how this behaves. We've seen outbreaks from this before," Karan said.
Doctors say that while hantavirus infections are rare, they can become severe.
"The fatality rate is usually 30% or 40%, the reason it's so tough is basically because the patient's immune system is basically deregulated," Karan said.
From 1980 to 2024, California has recorded 79 hantavirus infections, including one in Fresno County and seven in Mariposa County.
Health officials at the global, state and local levels continue to emphasize that the risk to the public remains low.
"This is not SARS-CoV-2. This is not the start of a COVID pandemic," Van Kerkhove said.
Officials also noted that reported hantavirus infections in California have involved a different strain known as the Sin Nombre virus.
President Donald Trump told ABC News he has been briefed on the situation and indicated his administration would be issuing a "full report" on the outbreak.
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