U.S. health officials are monitoring 16 additional people across the country for symptoms of hantavirus whom the Centers for Disease Control and Prevention has not previously mentioned, the agency said on Thursday.
The new people the C.D.C. reported were not on the cruise ship but were passengers on an April 25 flight to Johannesburg and exposed to someone known to have been infected, said Dr. David Fitter, who is leading the C.D.C.’s response to the outbreak.
The new total of those being monitored in the United States is 41, a significant increase over the 18 passengers from the Dutch cruise ship who were brought back to the United States on Monday. They are quarantining at special facilities in Omaha and Atlanta.
Seven other passengers from the cruise ship had disembarked on April 24 in St. Helena, an island in the Atlantic Ocean, returned to the United States on commercial flights and are being monitored by state health departments.
As of Thursday, there were no confirmed cases in the United States, Dr. Fitter said.
The infected passenger was a 69-year-old Dutch woman whose husband was the first person to die in the outbreak, on April 11. She was among those who disembarked from the ship on April 24. The next day, she flew from St. Helena to Johannesburg. She collapsed shortly after arrival and died on April 26. She was confirmed on May 4 to have had hantavirus.
C.D.C. officials would not give any other information about the 16 passengers, including where they had gone once they reached the United States.
It was not clear whether all Americans exposed to the virus are now back in the country, or whether there are additional people being monitored abroad.
“Our job is to ensure that we are monitoring and in contact with anybody that might have been on the flight this person had taken,” Dr. Fitter told reporters. The agency is “monitoring all Americans that potentially would have been exposed, whether in the U.S. or abroad, and we have been in contact with them,” he said.
In an interview on Sunday with CNN, Dr. Jay Bhattacharya, the C.D.C.’s acting director, said none of the seven passengers who returned to the United States earlier had symptoms at the time of their travel, so officials had not seen a need to alert the public or trace contacts.
For the moment, quarantine is essentially voluntary. Officials are encouraging those who were exposed to the virus to “stay at home and avoid being around people during their 42-day monitoring period,” Dr. Fitter said.
