KILLER coronavirus has "mutated" into two strains - with the most aggressive infecting 70 per cent of patients, scientists have claimed.

Researchers in China said they had found two main types of the deadly disease could be causing infections.

Read our coronavirus live blog for all the latest news and updates

3 Scientists in China studying the coronavirus outbreak said they had found two main types of the disease could be causing infections Credit: AFP or licensors

The bug, named Covid-19, has now infected at least 93,000 people and claimed the lives of 3,200 globally.

A team from Peking University's School of Life Sciences and the Institut Pasteur of Shanghai under the Chinese Academy of Sciences have been analysing the outbreak since it first emerged in December.

They say that early findings suggest there are two strains of the infection - one of them is more aggressive than the other and has infected more people.

But the scientists warned that their analysis examined a limited range of data - 103 samples - and said more research was needed.

Aggressive strain

The preliminary study found that when the virus first crossed into humans, the "ancestral" strain - which they named 'S' - subsequently evolved into another version, called 'L'.

In their study, they found that the older strain is the more aggressive and faster-spreading of the two.

Initially the newer strain, L, was more prevalent - but is now reducing and S has gone onto become more common.

The authors suggest that this could be because the disease it causes is less severe, meaning people can carry it for longer before they are hospitalised - making it the risk of passing it on greater.

3

They also claim that the more aggressive version associated with the disease outbreak in Wuhan accounted for about 70 per cent of analysed strains.

Meanwhile 30 per cent was linked to the less aggressive type, according to the findings, published on Tuesday in the National Science Review, the journal of the Chinese Academy of Sciences.

"These findings strongly support an urgent need for further immediate, comprehensive studies that combine genomic data, epidemiological data, and chart records of the clinical symptoms of patients with coronavirus disease 2019 (COVID-19)," they wrote.

But experts warn that the study is very early data and more research is needed.

3 South Korean army soldiers wearing protective gears move to spray disinfectant as a precaution against the new coronavirus Credit: AP:Associated Press

Dr Stephen Griffin, associate professor of infection and immunity at University of Leeds, said: “It is usually the case that when RNA viruses first cross species barriers into humans they aren’t particularly well adapted to their new host, i.e. humans.

"Thus, they usually undergo some changes allowing them to adapt and become better able to replicate within, and spread from human to human.

"However, as this study hasn’t tested the relative 'fitness' of these viruses when they replicate in human cells or an animal model, it isn’t really possible to say whether this is what’s happened to SARS-CoV2.

"It is also difficult to say how or why human interference may have impacted upon one strain relative to the other for similar reasons."



Incubation period

Also on Wednesday, one of China's top medical associations confirmed that the median incubation period of the coronavirus is five to seven days and the maximum 14 days.

The remarks by Du Bin, chairman of the critical care medical branch of the Chinese Medical Association, mark the most conclusive assessment of the virus' incubation period by a government-affiliated medical organization to date.

The revelations came amid a fall in new coronavirus cases following crippling restrictions imposed on the world's second largest economy to stop its spread, including transport suspensions and the extension of the Lunar New Year holiday.

Mainland China had 119 new confirmed cases of coronavirus on Tuesday, the National Health Commission said, down from 125 the previous day, in a broad trend that has seen numbers of new cases fall from the middle of February.

The total number of cases on the mainland has now reached 80,270. The number of deaths rose by 38 to bring the total toll for mainland China to 2,981 by March 3.

All but one new death occurred in Hubei province, the epicentre of the outbreak.

With the number of new daily infections overseas now exceeding new cases in China, Chinese officials have begun to seek ways to control the spread of the virus outside of China and guard against future outbreaks.

Authorities have asked overseas Chinese hoping to return home to reconsider their travel plans, while cities across the country have set up quarantine rules for those entering from high-risk places.

MORE ON CORONAVIRUS Live Blog VIRUS LIVE Huge spike in positive Covid tests as Eat Out To Help Out blamed for 167% leap PPE BOOST Care home staff to get free PPE as part of Govt's £550m war on winter Covid SNOT COVID Parents 'sinking testing system by ordering swabs for kids with the sniffles' SECOND SPIKE Hospitals told to clear beds as NHS braces for second Covid spike in two weeks 'DON'T WANNA HEAR IT' Welsh club let sick aces play in Europa League despite Covid outbreak GAME CHANGER Groundbreaking Covid test gives accurate on-the-spot result in 90 minutes FAST AND ACCURATE New 90-minute Covid test is 94% accurate and can be done at home PETS GASPING Cats and dogs suffering breathing problems after catching Covid, study claims TESTING TIMES Parents' anger as 1000s of kids with colds are sent home over Covid fears Exclusive DREAM JOB Brits offered chance to work from home on a beach in Barbados on a year-long visa

An infected person is known to have arrived in China from Iran, one of the virus' new hotspots, last week.

China is encouraging domestic producers of medical protective equipment to export protective suits to meet overseas demand as the virus spreads, Cao Xuejun, an official with China's Ministry of Industry and Information Technology said in a press briefing in Beijing on Wednesday.

China's health authorities are also studying setting up emergency reserves for medical resources and protective materials, Mao Qunan, an official at China's National Health Commission said at the same briefing.