Hantavirus live updates: American who initially tested positive now tests negative

California health officials on Monday released new information about four residents who were exposed to the hantavirus and are now being monitored, all of whom are currently healthy and not showing symptoms.

A South Bay resident from Santa Clara County was on the MV Hondius cruise ship but disembarked before the outbreak. Two other Californians were also on the ship and disembarked over the weekend in the Canary Islands. They are now in quarantine at a federal facility in Nebraska.

The fourth Californian, a Sacramento County resident, has returned home. That person was not on the ship but was exposed to someone who was ill on a plane in South Africa, according to health officials.

All four individuals are being closely monitored.

In the coming days, as the cruise ship passengers decide whether to stay at the University of Nebraska quarantine facility or self-monitor at home, those who opt to go home will not fly on a commercial flight, an official from the Centers for Disease Control and Prevention told ABC News. Passengers who opt to go home will have been assessed by health officials for any signs of illness.

-ABC News' Youri Benadjaoud

A doctor said the hantavirus will likely not have an outbreak like COVID or influenza because of how it is spread.

A doctor weighed in on hantavirus, after cases popped up on a cruise ship.

He said the threat to the public is very low.

There are likely 10 total hantavirus cases, including one American and one French passenger who tested positive after disembarking the ship, officials said.

Of the 18 U.S. residents who were repatriated, 16 are in Nebraska: the one who tested positive is in biocontainment and the 15 who did not test positive are in quarantine, officials said. The other two U.S. residents are in Atlanta, officials said.

Additionally, nine U.S. cruise ship passengers who disembarked prior to the outbreak being discovered are being monitored by state health departments, officials said. Two are in Texas, two are in Georgia, one is in Virginia, one is in Arizona and one is in California.

Another two Americans who were exposed during air travel are in New Jersey, officials said.