Human-to-human transmission has been confirmed in an outbreak of a new coronavirus, the head of a Chinese government expert team said Monday, as the total number of cases more than tripled and the virus spread to other cities in China.

Team leader Zhong Nanshan, a respiratory expert and head of the health commission team investigating the outbreak, said two people in Guangdong province in southern China caught the disease from family members, state media said.

Human-to-human transmission — spread from close contact, some such as among family members — could make the virus spread more quickly and widely, if it spreads easily. The outbreak is believed to have started from people who picked it up at a seafood market in the city of Wuhan in central China.

Zhong said the two people in Guangdong had not been to Wuhan but family members had returned from the city, the China Daily said.

The virus belongs in the same family of coronaviruses as Severe Acute Respiratory Syndrome (SARS), which killed nearly 800 people globally during a 2002-03 outbreak that started in Guangdong, China. In Canada, 44 people died, many of them health-care workers.

Symptoms include fever and difficulty in breathing, which are similar to many other respiratory diseases and pose complications for identifying cases.

Four have died.

The official Chinese Xinhua News Agency reported that as of 6 p.m. local time on Jan. 20, a total of 224 cases of the new coronavirus infection were reported in China, including 217 confirmed cases:

Five in Beijing.

14 in Guangdong.

198 in Wuhan.

There are also seven suspected cases: two in Sichuan, one in Yunnan Province, two in Shanghai, one in Guangxi Zhuang Autonomous Region, and one in Shandong Province.

In a statement posted on its official Weibo social media account, the Wuhan Municipal Health Commission said 15 medical workers in the city had been diagnosed, with pneumonia with one other suspected case. Of the infected staff, one was in critical condition, it added.

If health-care workers were not exposed at the seafood market but from an encounter with a patient then that's a signal, said Dr. Theresa Tam, Canada's chief public health officer.

It emphasizes the importance of standard infection prevention and control precautions, Tam said.

"It is important to take this seriously, and be vigilant and be prepared. But I don't think there's reason for us to panic or be overly concerned," Tam said.

World Health Organization director general Dr. Tedros Adhanom Ghebreyesus will convene an emergency committee on what it calls the novel coronavirus (2019-nCoV).

The committee will meet on Wednesday in Geneva to determine whether the outbreak constitutes a public health emergency of international concern, and what recommendations should be made to manage it.

A health worker monitors a thermal scanner as passengers arrive at Narita International Airport in Japan last week. The viral outbreak has put other countries on alert as millions of Chinese travel for Lunar New Year. (Tomohiro Ohsumi/Getty Images)

Declaring a global health emergency can bring more international attention and aid.

WHO has not recommended trade or travel restrictions.

Previous global emergencies have been declared for crises including the ongoing Ebola outbreak in Congo, the emergence of Zika virus in the Americas in 2016 and the West Africa Ebola outbreak in 2014.

Dr. Isaac Bogoch, an infectious disease physician at Toronto General Hospital, said Monday the key questions about the virus include:

How easily does it transmit between people, which is an important factor in how widespread the outbreak will ultimately get?

What is the source of the infection?

What proportion of people become severely ill or need hospitalization, compared with what proportion of people have few to no symptoms?

"This may be more widespread in China than it was earlier believed," Bogoch said.

Tam, Canada's chief public health officer, told reporters that there are no reported cases of this new coronavirus in Canada and the agency is not aware of any cases involving Canadians overseas.

There were three travellers from Wuhan who were investigated and ruled out in the last week, Tam said. She would not say where in Canada they were screened.

Zhong said the two people in Guangdong had not been to Wuhan but fell ill after family members had returned from the city, the China Daily said.

The outbreak has put other countries on alert as millions of Chinese travel for Lunar New Year.

Authorities in Thailand and in Japan have already identified at least three cases, all involving recent travel from China.

China says it is acting responsibly and openly to safeguard the world from the new coronavirus 0:38

South Korea reported its first case Monday, when a 35-year-old Chinese woman from Wuhan tested positive for the new coronavirus one day after arriving at Seoul's Incheon airport. The woman has been isolated at a state-run hospital in Incheon city, just west of Seoul, the Korea Centers for Disease Control and Prevention said in a statement.

At least a half-dozen countries in Asia and three U.S. airports have started screening incoming airline passengers from central China.

Bogoch said informing travellers to Canada is important so if anyone coming from China comes down with a respiratory illness knows where to go and what to do to seek care.

Chinese authorities published the genetic sequence of the virus. At Canada's National Microbiology Laboratory, scientists have developed a test for the virus, Tam said.

What are public health officials saying in Canada?

The virus belongs in the same family of coronaviruses as Severe Acute Respiratory Syndrome (SARS). Public Health Agency of Canada (PHAC) told CBC News Sunday that "the overall risk of disease spread to Canada is considered low."

Canada has no direct flights from Wuhan, and the volume of travellers arriving indirectly from Wuhan is low, PHAC said.

PHAC said it will be "implementing additional measures" in the coming week, including warning signs in English, French and simplified Chinese at airports in Toronto, Vancouver and Montreal. On the kiosks where people fill in questions, they'll be asked if they've been in an area affected by the outbreak within the last 14 days, Tam said.

If an ill passenger is referred for quarantine, their temperature could be taken as part of the assessment.

U.S. officials have said they will begin screening travellers coming from Wuhan at three major airports — New York City's JFK International Airport, San Francisco International Airport and Los Angeles International Airport.