In a rapid development, 14 new cases of novel coronavirus were identified in Italy on Friday, bringing the country's total to at least 16, Italian health officials reported. Many of the new cases were among people who had not traveled to China.
The cluster of cases in the Lombardy region triggered officials to suspend public gatherings, demonstrations and sporting events, as well as close schools, restaurants and businesses, in order to contain the virus, Roberto Speranza, Italy's health minister, said during a Friday news conference.
Meanwhile, Iranian authorities reported 18 cases of novel coronavirus and four deaths over the course of two days, the World Health Organization detailed at a Friday news conference. Lebanon also reported its first coronavirus case Friday, in a traveler from Iran, WHO officials said.
While the number of cases of novel coronavirus, officially known as COVID-19 is small, we're "concerned about the number of cases with no clear link or travel to China," said Dr. Tedros Adhanom Ghebreyesus, director general of the WHO. Four deaths in such a short period raises concerns that there's a wider number of infections in Iran.
"Our window of opportunity is narrowing," Tedros said, though he stopped short of calling the Iranian cases a tipping point in the outbreak. "We need to act quickly before it closes completely."
There have been at least 1,073 confirmed COVID-19 cases in 26 other countries, including the United States, and eight deaths reported outside of China, which brings the worldwide death toll to 2,247, according to the WHO, which has declared the outbreak a global health emergency.
In the United States, health officials announced a change to the way they count COVID-19 cases among Americans. Moving forward, the Centers for Disease Control and Prevention will separate cases among people repatriated on State Department charter flights from other cases.
So far, 21 Americans repatriated from either Wuhan, China, or from the Diamond Princess cruise ship, have tested positive for novel coronavirus. That group is considered at high risk for infection and health officials anticipate additional COVID-19 cases along those passengers.
Cases among repatriated Americans don't reflect general transmission and risk in the U.S., Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases explained at a Friday news conference.
Thirteen other Americans have tested positive, according to the CDC. On Friday, health officials in Sacramento, California, reported an additional travel-related case in an individual who returned from China in early February.
In total, at least 34 people in the U.S. have been diagnosed with novel coronavirus, according to the CDC.
"This new virus represents a tremendous public health threat," Messonnier said.
While there is no indication of community-wide transmission of novel coronavirus in the United States, there is "still the possibility in the future that this is going to spread," she added.
In China, hundreds of inmates have been infected with the novel coronavirus as the outbreak spreads to prisons across the country.
He Ping, an official at China's Ministry of Justice, told reporters at a daily briefing Friday that officials have been fired after more than 500 cases of the newly discovered virus were diagnosed in five prisons across three Chinese provinces, including Hubei, the epicenter of the outbreak. No deaths have been reported, he said.
The first cases of the new coronavirus emerged in December in Wuhan, the capital of Hubei province. Chinese authorities have since placed the city under lockdown, but containment of the illness remains a struggle.
As of Friday, China's National Health Commission said it had received 75,465 reports of confirmed cases and 2,236 deaths on the Chinese mainland. An additional 102 confirmed infections have been reported in the special administrative regions of Hong Kong and Macao as well as Taiwan, with two deaths in Hong Kong and one in Taiwan.
China saw a significant spike in cases last week as the Health Commission of Hubei Province began counting cases without waiting for laboratory tests. But on Thursday, it went back to recording only lab-confirmed positive cases and subtracted some cases where the lab results returned negative.
"We're glad that China has come back to that kind of counting," said Tedos, noting that the problem with clinically confirmed diagnoses is that it's not always clear whether clinically diagnosed patients have tested positive for the virus. Given the high number of cases in Wuhan, it's likely that they made the change temporarily because there weren't enough tests to meet the demand, he explained.
COVID-19 causes symptoms similar to pneumonia, ranging from the mild, such as a slight cough, to the more severe, including fever and difficulty breathing, according to the U.S. Centers for Disease Control and Prevention. There is no vaccine yet for the virus.
A cruise ship quarantined in Japanese waters is the largest center of infection outside China.
The Diamond Princess docked at the Japanese port of Yokohama on Feb. 3 and was placed under quarantine two days later, as passengers and crew tested positive for COVID-19. Since then, more than 600 people on board have been infected with the disease and two have died, according to Japan's Ministry of Health, Labor and Welfare.
All those aboard the vessel who were infected have been brought ashore for treatment, while the rest were confined to their rooms until the quarantine period ends. Passengers who have tested negative for COVID-19 have been disembarking the ship since Wednesday.
Princess Cruises, which operates the cruise ship, has canceled all Diamond Princess voyages through April 20 due to the "prolonged quarantine period." The cruise line is offering a full refund to all 2,666 guests, more than 400 of whom were from the United States.
The U.S. government evacuated more than 300 American passengers on two charter flights Monday, including 14 who had tested positive for the new coronavirus before takeoff. Roughly 60 Americans, some who were hospitalized and others who opted to stay on the ship, remain in Japan.
The State Department issued a travel warning Thursday, advising Americans to "reconsider travel by cruise ship to or within Asia."
ABC News' Karson Yiu and Conor Finnegan contributed to this report from Hong Kong.