Four out of 10 COVID-19 patients have ‘silent’ cases with ZERO symptoms

By Mark Waghorn via SWNS

Four in ten COVID-19 patients don't have symptoms, according to new research.

A global study of almost 30 million people found "silent"' cases are twice as big a threat as previously feared.

The pooled percentage of asymptomatic infections among those confirmed to have the disease was 40.5 percent.

Rates rose among certain groups including pregnant women (54%), air and cruise travellers (53%) and care home residents or staff (48%).

Corresponding author Professor Min Liu, of Peking University, Beijing, said: "The high percentage of asymptomatic infections highlights the potential transmission risk in communities."

The pooled data showed 4.5 percent of undiagnosed care home residents or staff had the coronavirus without displaying symptoms.

These include fever, cough, loss of taste or smell, fatigue and shortness of breath.

It also applied to over one in fifty pregnant women and air or cruise travellers.

Prof Liu said: "This finding of a high percentage of asymptomatic infections among air or cruise travellers suggests screening and quarantine on airport arrival is important for reducing community transmissions - especially in countries without local transmission."

The results are based on 95 studies involving 29,776,306 individuals from across the world, including the UK.

Overall, numbers of asymptomatic infections among tested populations was relatively low - 0.25 percent or one in 400.

But this soared to nearly 40 percent of those found to be carrying the virus.

Earlier evidence suggested one in five infected people experience no symptoms - and are less virulent than obviously ill peers.

Prof Liu said: "These findings suggest asymptomatic infections might contribute to transmission within the community."

She called for increased routine testing - especially in specific industries such as air transportation.

Prof Liu said: "In addition, we found approximately one-third of individuals with confirmed Covid-19 were asymptomatic among health care workers or in-hospital patients.

"Because asymptomatic health care workers might contribute to disease spread in and out of hospitals, surveillance is important for infection control and transmission reduction.

"Meanwhile, hand hygiene and personal protective equipment were necessary for hospital visitors."

The 'meta-analysis\ also found those under 39 were most likely to be asymptomatic - confirming previous research.

Prof Liu said: "This indicated young adults who often presented mild or no symptoms were a potential source of transmission in the community."

The study in JAMA Network Open is the biggest and most updated of its kind - covering Europe, the US, Africa, Asia and South America.

It included 19,884 people with confirmed Covid-19 - among whom 11,069 were asymptomatic.

Prof Liu said: "Our results could raise awareness among the public and policymakers and provide evidence for prevention strategies."

Last year a University College London study suggested at least 70 percent of Covid cases in the UK are asymptomatic.

Scientists say such carriers are just as likely to transmit the virus as those with a cough and fever.

Studies in Italy and Iceland have found almost half of coronavirus infections are asymptomatic.

Added Prof Liu: "Our results could be useful for strategies to reduce transmission by asymptomatic infections.

"Screening for asymptomatic infection is required, especially for countries and regions that have successfully controlled Covid.

"Asymptomatic infections should be under management similar to that for confirmed infections, including isolating and contact tracing."