SUNDAY, Feb. 23, 2020 (HealthDay News) -- The chances of a coronavirus pandemic continued to climb Sunday as multiple countries around the world raced to stem outbreaks of "untraceable" cases of the virus.

Clusters of cases arising in South Korea, Italy, Iran and Canada with no clear ties to outbreak's epicenter in China have heightened concerns about local, self-sustaining epidemics and a global pandemic. In a pandemic, outbreaks occur on more than one continent.

As reported Sunday by Associated Press, the list of countries with burgeoning case counts includes:

• South Korea. Total cases of COVID-19 have risen from just 28 last week to 602 by Sunday, with a jump of 298 cases in the past 48 hours. Six 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. The president of South Korea put the country on its highest alert Sunday, ordering officials to take "unprecedented and powerful" actions to curb the spread of coronavirus. These actions can include closing schools and public transportation temporarily. Officials said the re-opening of schools following a spring break will be delayed until March 9.
• Italy. Officials announced Sunday that the number of new cases reported jumped to 132, with 89 of those cases reported in the past 24 hours. Most of the cases have been reported in the northern region of Italy, an area that includes Milan. Local officials have been racing to close down towns where the virus has surfaced. Meanwhile, officials in Venice halted its annual Carnival, an international gathering that draws people from all over the world, after three cases of coronavirus were reported there. Italy now has the largest number of cases outside Asia.
• Iran. So far, Iranian officials say 43 cases have been identified and eight people have died. 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.
• Singapore. Five coronavirus case clusters have also emerged in that country, bringing the total number of cases to 89 on Sunday.

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 Sunday, the total number of cases within mainland China had reached more than 76,396, CNN reported, with 2,442. 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 35 on Friday, as U.S. health officials reported that more repatriated passengers evacuated from a quarantined cruise ship in Japan have tested positive for the virus.

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

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.

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.