More than 100 Americans cannot return home for at least two more weeks, after having been on a cruise ship in Japan that is a hot spot for the coronavirus, the United States Centers for Disease Control and Prevention said Tuesday.
“To protect the health of the American public,” the agency said, “all passengers and crew of the ship have been placed under travel restrictions, preventing them from returning to the United States for at least 14 days after they had left the Diamond Princess.”
Before anyone who was on the ship will be allowed to travel to the United States, he or she must go two weeks without showing symptoms of Covid-19, the disease caused by the coronavirus, or testing positive for it.
“If an individual from this cruise arrives in the United States before the 14-day period ends,” the C.D.C. said, “they will still be subject to a mandatory quarantine until they have completed the 14-day period with no symptoms or positive coronavirus test results.”
The decision to, in effect, tell Americans who traveled on the Diamond Princess to stay away followed a steady, steep increase in the number of infections in people who have been aboard it. That suggested that efforts to control the spread there may have been ineffective.
Updated Feb. 10, 2020
What is a Coronavirus?
It is a novel virus named for the crown-like spikes that protrude from its surface. The coronavirus can infect both animals and people, and can cause a range of respiratory illnesses from the common cold to more dangerous conditions like Severe Acute Respiratory Syndrome, or SARS.
How contagious is the virus?
According to preliminary research, it seems moderately infectious, similar to SARS, and is possibly transmitted through the air. Scientists have estimated that each infected person could spread it to somewhere between 1.5 and 3.5 people without effective containment measures.
How worried should I be?
While the virus is a serious public health concern, the risk to most people outside China remains very low, and seasonal flu is a more immediate threat.
Who is working to contain the virus?
World Health Organization officials have praised China’s aggressive response to the virus by closing transportation, schools and markets. This week, a team of experts from the W.H.O. arrived in Beijing to offer assistance.
What if I’m traveling?
The United States and Australia are temporarily denying entry to noncitizens who recently traveled to China and several airlines have canceled flights.
How do I keep myself and others safe?
Washing your hands frequently is the most important thing you can do, along with staying at home when you’re sick.
Passengers on board the Diamond Princess have been kept in quarantine off Yokohama since Feb. 4, but it is not clear how well they have been kept apart from one another. It was also unclear or whether the virus could somehow have spread on its own from room to room.
“It may not have been sufficient to prevent transmission,” the disease centers said in a statement Tuesday. “C.D.C. believes the rate of new infections on board, especially among those without symptoms, represents an ongoing risk.”
By Tuesday, 542 cases among people who have been on the ship had been confirmed, Japan’s health ministry said. That is more than half of all reported infections outside China.
Part of the problem is that it is not always immediately clear if someone has been infected with the virus, even when they are examined.
Earlier this week, the United States repatriated more than 300 passengers from the Diamond Princess and placed them in a 14-day quarantine at military bases.
On Tuesday, some of the passengers said American authorities had notified them that members of the group who had appeared to be disease-free in Japan tested positive for the virus after arriving in the United States.
The decision to temporarily bar passengers from traveling to the United States applies both to those who have tested positive and are hospitalized in Japan, and those who are still aboard the ship and not showing any sign of the illness.