Coronavirus ‘super-spreaders’ a potential risk as strain spreads from Wuhan to cities outside of China

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An expert in China said one ill patient spread the virus to 14 medical professionals.

One of China’s top health experts is warning of the potential for “super-spreaders” to worsen the impact of the new coronavirus strain, which can now be passed from human to human.

Key points:

  • Super-spreaders are people who, due to a number of factors, infect many others
  • The term first came into common use during the 2002-2003 SARS outbreak
  • No coronavirus super-spreaders have been reported but information is still emerging

Zhong Nanshan, the leader of an expert team sent to the city of Wuhan to investigate the deadly virus, told the South China Morning Post there was evidence one patient alone had spread the disease to 14 medical workers.

There have now been around 300 confirmed coronavirus infections, with six deaths. The majority of the cases have been in China, but people have also been diagnosed in Thailand, South Korea, Japan and Taiwan.

This morning there was confirmation the virus had spread to the US, with a man in his 30s being treated in a Seattle hospital. All those who have been diagnosed so far have spent time in China.

A Brisbane man was tested for the strain after returning from Wuhan with flu-like symptoms,but he was released from home isolation shortly after because he exhibited no symptoms of the virus. Queensland Health is still waiting on additional tests.

Dr Zhong said stopping the emergence of super-spreaders was “key to controlling the spread of the virus”, but with the busy Lunar New Year travel period underway an increase in infections was expected.

So what exactly is a super-spreader, and what can be done to prevent them infecting other people?

Here’s what you need to know.

What is a super-spreader?

A super-spreader is essentially a person who, for a number of reasons, spreads an infectious disease to many other people, frequently the medical workers treating them.

two people in blue medical gowns hair netting and face masks carry a tub along a road outside near a car

Kanta Subbarao, the director of the WHO Collaborating Centre for Reference and Research on Influenza at the Peter Doherty Institute for Infection and Immunity, told the ABC the term first really came into use during the 2002-2003 SARS coronavirus outbreak.

What is a coronavirus?

What is a coronavirus?

Here’s what we know about the novel coronavirus, or 2019-nCoV, and how worried you should be.

“With many viruses that transmit from person to person, there’s a general idea of how many people can be infected from the same source,” she said.

“With the super-spreaders — particularly with SARS — it became clear that there were some individuals, a few people, whose infections led to a larger number of secondary infections.

“That’s what people watch for when novel viruses emerge: whether there are some people who might serve as a source for larger dissemination, or dissemination to a larger number of people than others.”

Professor Subbarao said these secondary infections largely affected the healthcare workers treating the patients, as well as other people they had been in contact with.

Allen Cheng, an infectious disease and epidemiology expert at Monash University, said it was not known if these secondary infections had to do with the amount of SARS virus super-spreaders were shedding, or if it was because they had come into contact with a lot of people.

Have any super-spreaders been identified?

Medics check the temperatures of passengers on a flight from Wuhan to Macau.

Not yet — and thankfully super-spreaders are rare, according to Professor Subbarao.

Professors Cheng and Subbarao said it remained unclear if super-spreaders would even be a factor in the Wuhan coronavirus outbreak because information was still emerging, including on the total number of potential infections.

“This is early days; we don’t have a lot of information yet and we’re all waiting to see more of the facts as they emerge in scientific publications,” Professor Subbarao said.

“Trying to figure out if there are super-spreaders will really require a lot more epidemiologic information than we currently have.

“I’m sure this is an area that [health authorities] are looking into quite closely.”

Unfortunately, super-spreaders can only be identified after they have infected a large number of people.

However Professor Subbarao said she thought it would be quite unusual for a super-spreader to not show any symptoms of illness because they usually ended up in hospitals or other health facilities.

“What we learned from the SARS outbreak … and we learned this with the MERS coronavirus as well … is that the people that have been the source of large numbers of infection have been symptomatic and they’ve often been in medical care facilities,” she said

Lunar New Year travel a risk factor

Celebrations around the Lunar New Year spring festival are adding an extra element of risk to the situation. 

A traveller wears a face mask as he walks outside of the Beijing Railway Station with a crowd of people.

The annual event sees the largest annual movement of people in the world. During the festival, people from all over China travel back to their hometowns to spend time with family, creating huge pressure on the country’s public transport networks.

This means billions of train trips over a matter of days, with tickets at packed train stations often hard to come by. Some people also use the holiday period to travel abroad.

“It’s certainly something that potentially could lead to spread when people travel, and if they’re incubating the virus or ill with it, and yet they travel, they may expose many more people to the pathogen,” Professor Subbarao said.

“We don’t have a great handle on the incubation period, so people could make their plans and travel before they become symptomatically ill.”

A huge throng of passengers wait for their trains at the Hangzhou East Railway Station.

With the situation still evolving, Professor Subbarao said experts were waiting for more facts to emerge about the new coronavirus strain.

“There’s no reason to panic, but on the other hand we are all waiting for more information,” she said.