Melbourne epidemiologist Ivo Mueller told the Australian Science Media Centre: 'If the same pattern is repeated elsewhere, this means that in countries that only test symptomatic cases, the true burden of infections may be five times higher than now reported'.
The findings could be important as lockdown restrictions begin to be eased, and they highlight the need for accurate data on how many people worldwide have been infected, journal joint editor-in-chief Alan Smyth said in a linked blog.
A new study which looked at cruise ship passengers during the current pandemic has found that there may be more "silent" cases of Covid-19 than previously thought.
The first recorded fever on board the ship was on day eight and the study authors said from that point all passengers were confined to their cabins and surgical masks were issued, while full personal protective equipment was used for any contact with any patients with a fever.
"Even those who develop mild cases of Covid-19 are capable of producing antibodies that remain present at least 40 days after the appearance of symptoms".
Researchers said 128 people tested positive and the majority - 81 per cent - were asymptomatic.
The study authors conclude that the prevalence of COVID-19 infection on cruise ships is likely to be "significantly underestimated", prompting them to recommend that passengers should be monitored after disembarkation to ward off potential community spread of the virus.
In April, researchers analysed blood samples from 160 staff who had shown classic Covid-19 symptoms such as fever, breathing difficulties and loss of the sense of smell, but whose cases did not become serious enough to require hospitalisation.
By day 13, eight passengers and crewmembers - many of whom were over the age of 60 or had underlying conditions - required medical evacuation for respiratory failure.
"As countries progress out of lockdown, a high proportion of infected, but asymptomatic, individuals may mean that a much higher percentage of the population than expected may have been infected with COVID", he suggests.
In 10 instances, two passengers who shared the same cabin did not return the same test result - possibly due to the substantial number of false negative results associated with current swab testing methods.
And the potentially high rate of false negative results obtained with the current swab tests suggests that secondary testing is warranted, they add.
"It is hard to find a reliable estimate of the number of COVID-positive patients who have no symptoms", but the rate of 1% suggested by the World Health Organization in early March is far lower than that on the cruise ship in this study, Smyth said in his blog.
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We are also told that some of these people did not die OF Covid-19, but were displaying the symptoms at their time of death. The ONS said next week's figures will be a better representation of any trend, as it will not include bank holidays.