London - Cases of "silent" coronavirus may be much higher than thought after a study found more than 80 percent of sufferers had no symptoms.
Tests carried out on passengers and crew on board a cruise ship found almost six in ten had Covid-19 – yet under a fifth of them ever developed symptoms. Experts say it suggests many more have had the disease and built up immunity, reducing the chances of a second peak.
The ship – which had the researchers on board – departed from Ushuaia, Argentina, for a 21-day cruise of the Antarctic. It set sail in mid-March.
The first case of fever was reported on day eight, prompting the immediate adoption of infection control measures such as confining passengers to their cabins.
WATCH: WHO warns of second peak to first wave
Eight passengers and crew eventually required medical evacuation to hospital in Uruguay on day 13. On day 20 all the remaining 217 passengers and crew were swab tested for coronavirus, with 128 testing positive. Of those testing positive, 24 (19 percent ) had symptoms, but 108 (84 percent) were asymptomatic.
This is in stark contrast with the suggestions in early March by the World Health Organization (WHO) that only around one percent of cases are thought to be asymptomatic.
The findings, which are published in journal Thorax, comes as countries where coronavirus infections are declining could still face an “immediate second peak” if they let up too soon on measures to halt the outbreak, WHO warned.
The world is still in the middle of the first wave of the coronavirus outbreak, WHO emergencies head Dr Mike Ryan told an online briefing, noting that while cases are declining in many countries they are still increasing in Central and South America, South Asia and Africa, CNBC reported.