Seventeen more people in central China have been diagnosed with a new form of viral pneumonia that has killed two patients and placed other countries on alert as millions of Chinese travel for Lunar New Year holidays.

In total, 62 cases of the novel coronavirus have been identified in the central city of Wuhan, where the virus appears to have originated.

The Wuhan Municipal Health Commission reported the new cases in a statement Sunday.

Nineteen of those individuals have been discharged from the hospital, while two men in their 60s - one with severe preexisting conditions - have died from the illness.

Pedestrians wear protective masks as they walk through a shopping district in Tokyo on Thursday. Japan's government said Thursday a man treated for pneumonia after returning from China has tested positive for the new coronavirus identified as a possible cause of an outbreak in the Chinese city of Wuhan

A notice for passengers from Wuhan, China, is displayed near a quarantine station at Narita airport in Narita, Japan, on Thursday

JFK (above), LAX, and San Francisco were the first three US airports to begin screenings for the new coronavirus

Eight are in critical condition.

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

The list includes Thailand and Japan, which have together reported three cases of the disease in people who had come from Wuhan.

In the most recently diagnosed group, ages ranged between 30 and 79, Wuhan's health commission said.

WHAT IS THE NEW CORONAVIRUS SPREADING FROM CHINA? An outbreak of pneumonia-like illnesses began in Wuhan, China, at the end of 2019. Its symptoms are typically a fever, cough and trouble breathing, but some patients have developed pneumonia, a potentially life-threatening infection that causes inflammation of the small air sacs in the lungs. Scientists in China recognized its similarity to two viruses that turned into global killers: SARS and MERS. SARS, or severe acute respiratory syndrome is caused by the SARS coronavirus, known as SARS Co, and first emerged in China in 2002. By the end of the outbreak, the virus had spread to several other Asian countries as well as the UK and Canada, killing 774. MERS, or Middle East respirator syndrome originated in the region for which it's named, ultimately killed 787 people and belongs to the same family of coronaviruses as SARS. The new virus wasn't a match for either of those two, but it did belong to the same coronavirus family. Coronaviruses are a large family of pathogens, and most cause mild respiratory infections - i.e. the common cold. But because the SARS and MERS proved deadly, the emergence of another new coronavirus has health officials on edge around the world. Like its two dangerous cousins, the new coronavirus appears to have originated with animals - particularly seafood, chickens, bats, marmots - found at a Wuhan market that's been identified as the epicenter of the outbreak. The symptoms of SARS, which may be similar to those of the new coronavirus, include: a high temperature (fever)

extreme tiredness (fatigue)

headaches

chills

muscle pain

loss of appetite

diarrhoea After these symptoms, the infection will begin to affect your lungs and airways (respiratory system), leading to additional symptoms, such as: a dry cough

breathing difficulties

an increasing lack of oxygen in the blood, which can be fatal in the most severe cases So far, there isn't a treatment for the new virus or SARS, though the new virus has been sequenced, allowing for rapid diagnostics. Advertisement

Their initial symptoms were fever and a cough.

The health commission's statement did not say whether these patients had visited the Huanan Seafood Wholesale Market, which has been suspended after many infected individuals reported having either worked at or visited the venue.

Li Gang, director and chief physician of the Wuhan Centre for Disease Control and Prevention, told state broadcaster CCTV that 'the infectivity of the new coronavirus is not strong.'

Infectivity refers to how rapidly the virus may spread between individuals.

Most patients are experiencing mild symptoms, Li said, and no related cases have been found in more than 700 people who came into close contact with infected patients.

This 'does not rule out the possibility of limited human-to-human transmission, but the risk of continuous human-to-human transmission is low,' Li said. 'With the implementation of our various prevention and control measures, the epidemic can be prevented and controlled.'

The Chinese government is keen to avoid a repeat of SARS, or severe acute respiratory syndrome, another coronavirus that started in southern China in late 2002 and spread to more than two dozen countries, killing nearly 800 people.

Centers for Disease Control and Prevention (CDC) officials have created questionnaires about symptoms of the newly identified virus to distribute to passengers.

Passengers with symptoms will then be questioned more thoroughly and examined for fevers and undergo a diagnostic test for the virus on-site before potentially being referred to off-site and unidentified quarantine and assessment facilities.

CDC officials say that the risk of exposure is currently considered low, but Dr Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases said she thinks that it's 'more than likely that we'll see at least a case in the US' before the outbreak is over.

Dr Martin Cetron, director of the CDC's Division of Global Migration and Quarantine, said he estimates some 5,000 passengers will be screened in the US in the coming weeks.

So far, Wuhan has not been conducting exit screens, but he said they may begin doing so.

'The current risk from this virus to the general public is low,' said Dr Messonnier during a Friday call with reporters.

'For a family sitting around the dinner table tonight, it's not something they need to worry about.'

Nonetheless, she and the CDC are taking every precaution when it comes to protecting the US from the novel coronavirus that emerged at the end of last year in Wuhan.

'Any time there is a new virus or pathogen in a population that we've never seen before, it's concerning, because that population doesn't have existing immunity, treatment or vaccines,' said Dr Messonnier.

'We're especially concerned [by the new coronavirus] because we have the precedents of SARS and MERS and those were difficult outbreaks with many illnesses and deaths.