SATURDAY, Feb. 22, 2020 (HealthDay News) -- Outbreaks of "untraceable" cases of coronavirus in multiple countries around the world are raising the real possibility of a pandemic, public health experts say.

Clusters of cases arising in South Korea, Iran, Italy and Canada with no clear ties to the outbreak's epicenter in China have boosted concerns about local, self-sustaining epidemics and a global pandemic.

As reported Saturday by CNN, the list of countries with burgeoning case counts includes:

• South Korea. Total cases of COVID-19 have risen from just 28 last week to 433 by Saturday, with a jump of 229 cases in just over the past 24 hours. Two people have died. Most cases are centered in the southern city of Daegu, and more than half are concentrated among members of the Shingeongji religious group. "We have secured a list of about 9,300 members of the relevant religious group, and we are preemptively enforcing self-isolation and facility isolation," Kim Gang-lip, South Korea's vice minister of health, said at a press briefing.
• Iran. So far, Iranian officials say 28 cases have been identified and five people have died -- bringing the global death toll from coronavirus outside Asia to 17. It's thought that a Chinese worker who'd returned to the Iranian city of Qom may have been the source for the Iranian cases there, although cases are arising elsewhere. Minnou Mohraz, a member of the National Committee for Infectious Diseases at Iran's Ministry of Health, said the outbreak "started in Qom and has reached other cities in the country like Tehran, Babol, Arak, Isfahan, Rasht and other cities due to people traveling. There is a possibility that it exists in all cities across the country."
• Canada. Theresa Tam, Canada's chief public health officer, said Friday that investigation was underway after a Canadian tested positive for COVID-19 after returning from Iran. The patient had not been to Qom. "Any important cases linked to Iran could be an indicator that there is more widespread transmission than we know about," Tam said.

According to the Associated Press, five coronavirus case clusters have also emerged in Singapore, and officials in Italy are trying to track down and contain cases in the northern part of that country.

Speaking to the AP, one expert said that the mild nature of most cases of COVID-19 is making the virus tough to spot and contain. People with symptoms that might simply be taken for cold or flu may be transmitting the virus to others, explained Dr. Amesh Adalja of the Johns Hopkins Center for Health Security in Baltimore.

"If that's the case, all of these containment methods are not going to work," Adalja told the AP. "It's likely mixed in the cold and flu season all over the place, in multiple countries.

By Saturday, the total number of cases within mainland China has reached more than 76,200, CNN reported, with 2,372 deaths reported worldwide. The rate of new cases is slowing in China, suggesting that draconian efforts to contain the outbreak there are working.

Cruise ship cases spur uptick in U.S. numbers

In the meantime, the number of coronavirus cases among Americans jumped to 34 on Friday, as U.S. health officials reported that more passengers who were evacuated from a quarantined cruise ship in Japan have tested positive for the virus.

"We have 13 U.S. cases, versus 21 cases among people who were repatriated," Dr. Nancy Messonnier, director of the U.S. National Center for Immunization and Respiratory Diseases, said during a media briefing Friday. "The repatriated cases include 18 passengers from the Diamond Princess [cruise ship] and three from the Wuhan repatriation flights."

However, nearly everyone else evacuated in the special flights from Wuhan have finished their 14-day quarantine, Messonnier added.

Of the Diamond Princess patients who are now in the United States, 11 are receiving care at the University of Nebraska Medical Center, five are receiving care around Travis Air Force Base in northern California and two are being cared for around Lackland Air Force Base in Texas, Messonnier said.

"Because the passengers on the Diamond Princess were in a close setting where there has been a significant spread of COVID-19, they are considered at high risk for infection and we do expect to see additional confirmed cases," she noted.

Ten more passengers from the Diamond Princess tested positive for coronavirus in Japan, but they are not being counted among the infected yet because the tests have not been confirmed by the U.S. Centers for Disease Control and Prevention, Messonnier said.

"We never expected that we would catch every single traveler with novel coronavirus returning from China, given the nature of this virus and how it's spreading," Messonnier said during the briefing. "That would be simply impossible."

Buying time

Instead, the measures being taken are buying health officials time for a response before the virus gains a foothold in the United States, she explained.

Among the 400 Americans who were on board the Diamond Princess cruise ship, roughly 300 were evacuated a week ago and are under quarantine in the United States.

For the patients who have been sent to the University of Nebraska Medical Center, the facility has a biocontainment unit and is specially designated to treat highly infectious diseases, CNN reported. The unit successfully treated three patients for Ebola in 2004.

More than 100 American passengers remain in Japan, and U.S. health officials announced Tuesday that they will not be allowed to return home for at least two more weeks.

According to a statement from the CDC, containment measures that were taken on the ship "may not have been sufficient to prevent transmission. [The] CDC believes the rate of new infections on board, especially among those without symptoms, represents an ongoing risk."

Passengers who stayed on the ship will not be allowed to return to the United States until they have been off the ship for 14 days, without any symptoms or a positive test for the virus, the agency added. The ruling also applies to Americans who are hospitalized for coronavirus in Japan.

Earlier this month, the United States began to bar entry to any foreigners who have recently traveled to China. U.S. citizens who have recently traveled to the Hubei province of China, where Wuhan is located, will be quarantined for up to 14 days, U.S. health officials said. U.S. citizens who have recently traveled to other parts of China will face health screenings and voluntary quarantines of up to 14 days.

The temporary entry ban applies to foreign nationals, with the exception of relatives of citizens and permanent residents.

More information

The U.S. Centers for Disease Control and Prevention has more on the new coronavirus.