New fears have emerged about the threat of ‘mystery’ virus hMPV which is behind wave of hospitalisations in China, it has been claimed, and is now on the rise globally.

Middle-aged patients have tested positive for the virus and developed pneumonia ‘between three and five days later’, according new unconfirmed reports, based on videos shared via Chinese social media app Weibo.

Another Weibo user said that, according to the YouTube channel Decoding China, the situation was ‘worse than in 2022’, when a Covid-19 outbreak in Shanghai led to mass testing and strict lockdown conditions. 

Concerns were first raised in early January when footage emerged of hospitals in China apparently overrun, drawing comparisons with with the early days of Covid.

The videos show patients in face masks crowding A&Es and parents holding sick children in long lines in pediatric units.

Local news reports blamed hMPV — human metapneumovirus — a little known but not uncommon bug which normally causes a mild cold-like illness.

The elderly, very young and those with pre-existing illness can be worst affected. 

The US Centers for Disease Control reports that 2.2 percent of tests conducted across America in the week ending January 4 were positive for hMPV, up 25 percent in a week 

As with all respiratory infections, one major risk is pneumonia, a potentially fatal lung condition, which can develop within days.

Experts globally called on Chinese authorities to reveal crucial details of the outbreak as cases began to surge in the UK and America.

According to UK surveillance data, roughly one in 20 non-flu respiratory infections are now due to hMPV — more than double the number in early December.

And in the US, the Centers for Disease Control yesterday reported that one in 50 Americans with a cough likely had the virus — and increase of 25 per cent within a week. 

Despite this the numbers are not unusual for this time of year and doctors reassured Americans that hMPV is mild for most.

The World Health Organisation also attempted to quell growing uncertainty, adding the situation in China was ‘not unusual’. 

The global health agency said rates of respiratory infections there were within the normal range expected for winter, with no unusual outbreaks reported.

Health officials have also claimed infections had peaked and were now going down.

hMPV belongs to the same family as the respiratory syncytial virus (RSV) and usually causes little more than a fever, cough and nasal congestion 

Concerns were first raised in early January when footage emerged of hospitals in China apparently overrun, drawing comparisons with with the early days of Covid 

‘At present, the rate of positive cases in hMPV detection is fluctuating and the rate of positive cases in northern provinces is declining,’ said Wang Liping, a researcher at the Chinese Center for Disease Control and Prevention, on Sunday.

The new footage, which has not been viewed by MailOnline, may add pressure for health chiefs to offer an update, in order to reassure the public. 

hMPV belongs to the same family as the respiratory syncytial virus (RSV) and usually causes little more than a fever, cough and nasal congestion.

The virus was first ‘discovered’ in 2001 but it thought to have been one of the numerous bugs in circulation that cause common colds for many decades, if not longer.

Speaking last week, virus expert Dr Andrew Catchpole said: ‘hMPV is usually detected in the winter periods but it does seem that the rates of serious infection may be higher in China than what we would expect in a normal year. 

He added: ‘It is unclear just how high the numbers are or if issues are arising purely due to coinciding with high flu and Covid levels.’

Dr Catchpole noted that while hMPV ‘does mutate and change over time with new strains emerging’, it is ‘not a virus considered to have pandemic potential’.