Saudi Press

Saudi Arabia and the world
Thursday, Oct 02, 2025

Big pool of coronavirus cases going undetected, German researchers say

Big pool of coronavirus cases going undetected, German researchers say

Widespread testing and isolation of infected people ‘needed to stop renewed outbreak’. About 6 per cent of cases identified worldwide, study estimates

Most coronavirus cases around the world go undetected, raising the risk of fresh outbreaks if social distancing measures and travel restrictions are lifted too early, researchers have warned.

The researchers, from the University of Gottingen in Germany, made the assessment after comparing estimates of coronavirus infection fatality rates in a previous study with the confirmed number of cases and United Nations population data.

They concluded that on average about 6 per cent of cases were detected in the 40 countries studied, and the only way to prevent a renewed outbreak of Covid-19, the disease caused by the coronavirus, was to do widespread testing followed by isolation of infected people.

“Once we are able to guarantee that this can be done, we can talk about relaxing restrictions. This is why increasing testing capacity is so important,” said Christian Bommer, from the Centre for Modern Indian Studies and a co-author of the paper with Sebastian Vollmer.



The paper was posted on the websites of the university and German education ministry, but it has not been published on a preprint server or in an academic journal.

Vollmer and Bommer calculated the detection rate using an estimate of the infection fatality rate published on The Lancet Infectious Diseases site on March 30. The authors of the Lancet study estimated that 0.66 per cent of people who became infected died.

The German researchers then divided the number of deaths on a given date by this infection fatality rate and compared this to the number of reported cases 14 days earlier, the estimated time period between diagnosis and death, also based on the Lancet study.

Adjusting for differences in age groups using UN population data, they calculated detection rates for 40 countries.

South Korea had the highest detection rate at almost 50 per cent while the US was 1.5 per cent. Turkey had the lowest detection rate at 0.12 per cent. On average, the detection rate globally might only be 6 per cent, they said.

Vollmer and Bommer concluded that the actual number of infections worldwide could be in the tens of millions.

“These results mean that governments and policymakers need to exercise extreme caution when interpreting case numbers for planning purposes,” Vollmer said.

“Such extreme differences in the amount and quality of testing carried out in different countries mean that official case records are largely uninformative and do not provide helpful information.”

Alex Cook from the National University of Singapore, who specialises in infectious diseases modelling, agreed that Covid-19 cases were under-reported because some cases involved asymptomatic infections and people with mild symptoms who might not realise they had the virus.



But the paper was limited by the estimates used in the Lancet study.

“That study does have quite a lot of uncertainty on the infection fatality rate, which could be as low as 4 to as high as 13 in 1,000 infections,” Cook said.

He said blood tests for antibodies would be a reliable way to find out how many people in the population had been infected already.

But the scale of the tests would depend on how far a population was through the epidemic.

For example, if 1 in 1,000 people in Hong Kong had been infected, a survey of 1,000 would be limited as there was a good chance that no positive cases would turn up, Cook said.

“On the other hand, maybe in Wuhan 10 per cent of the population has been infected, in which case a survey of 1,000 would tell you that to within a reasonable margin of error,” Cook said.



Benjamin Cowling, the head of epidemiology and biostatistics at Hong Kong University’s school of public health, said he thought the modelling by the German researchers was reasonable. His own estimate would follow a similar calculation and Cowling agreed the number of infections globally could be more than 10 million people already.

Another factor was the health systems of each country, Bommer said.

While he and Vollmer accounted for the different mortality rates in age groups using UN population data, they lacked data for the differences in medical care in each country, which also affects the mortality rate.

“Countries with good health systems are likely to do better than China, so for countries like Germany and France, our estimates are likely conservative. They might be even worse at detecting infections than what we estimate,” Bommer said.

The paper estimated Germany’s detection rate at 16 per cent, and France at 3 per cent.

Newsletter

Related Articles

Saudi Press
0:00
0:00
Close
Altman Says GPT-5 Already Outpaces Him, Warns AI Could Automate 40% of Work
Trump Organization Teams with Saudi Developer on $1 Billion Trump Plaza in Jeddah
Electronic Arts to Be Taken Private in Historic $55 Billion Buyout
Colombian President Petro Vows to Mobilize Volunteers for Gaza and Joins List of Fighters
Nvidia and Abu Dhabi’s TII Launch First AI-&-Robotics Lab in the Middle East
UK, Canada, and Australia Officially Recognise Palestine in Historic Shift
New Eye Drops Show Promise in Replacing Reading Glasses for Presbyopia
Dubai Property Boom Shows Strain as Flippers Get Buyer’s Remorse
Top AI Researchers Are Heading Back to China as U.S. Struggles to Keep Pace
JWST Data Brings TRAPPIST-1e Closer to Earth-Like Habitability
UAE-US Stargate Project Poised to Make Abu Dhabi a Global AI Powerhouse
Trump and Starmer Clash Over UK Recognition of Palestinian State Amid State Visit
Saudi Arabia cracks down on music ‘lounges’ after conservative backlash
Saudi Arabia Signs ‘Strategic Mutual Defence’ Pact with Pakistan, Marking First Arab State to Gain Indirect Access to Nuclear Strike Capabilities in the Region
Sam Altman sells the 'Wedding Estate' in Hawaii for 49 million dollars
Turkish car manufacturer Togg Enters German Market with 5-Star Electric Sedan and SUV to Challenge European EV Brands
World’s Longest Direct Flight China Eastern to Launch 29-Hour Shanghai–Buenos Aires Direct Flight via Auckland in December
New OpenAI Study Finds Majority of ChatGPT Use Is Personal, Not Professional
Kuwait opens bidding for construction of three cities to ease housing crunch.
This Week in AI: Meta’s Superintelligence Push, xAI’s Ten Billion-Dollar Raise, Genesis AI’s Robotics Ambitions, Microsoft Restructuring, Amazon’s Million-Robot Milestone, and Google’s AlphaGenome Update
Indian Student Engineers Propose “Project REBIRTH” to Protect Aircraft from Crashes Using AI, Airbags and Smart Materials
Could AI Nursing Robots Help Healthcare Staffing Shortages?
Turkish authorities seize leading broadcaster amid fraud and tax investigation
Qatari prime minister says Netanyahu ‘killed any hope’ for Israeli hostages
Apple Introduces Ultra-Thin iPhone Air, Enhanced 17 Series and New Health-Focused Wearables
Big Oil Slashes Jobs and Investments Amid Prolonged Low Crude Prices
Social Media Access Curtailed in Turkey After CHP Calls for Rallies Following Police Blockade of Istanbul Headquarters
Did the Houthis disrupt the internet in the Middle East? Submarine cables cut in the Red Sea
Gold Could Reach Nearly $5,000 if Fed Independence Is Undermined, Goldman Sachs Warns
Uruguay, Colombia and Paraguay Secure Places at 2026 World Cup
Trump Administration Advances Plans to Rebrand Pentagon as Department of War Instead of the Fake Term Department of Defense
Tether Expands into Gold Sector with Profit-Driven Diversification
Trump’s New War – and the ‘Drug Tyrant’ Fearing Invasion: ‘1,200 Missiles Aimed at Us’
At the Parade in China: Laser Weapons, 'Eagle Strike,' and a Missile Capable of 'Striking Anywhere in the World'
Information Warfare in the Age of AI: How Language Models Become Targets and Tools
Israeli Airstrike in Yemen Kills Houthi Prime Minister
After the Shock of Defeat, Iranians Yearn for Change
YouTube Altered Content by Artificial Intelligence – Without Permission
Iran Faces Escalating Water Crisis as Protests Spread
More Than Half a Million Evacuated as Typhoon Kajiki Heads for Vietnam
HSBC Switzerland Ends Relationships with Over 1,000 Clients from Saudi Arabia, Lebanon, Qatar, and Egypt
Sharia Law Made Legally Binding in Austria Despite Warnings Over 'Incompatible' Values
Dogfights in the Skies: Airbus on Track to Overtake Boeing and Claim Aviation Supremacy
Tim Cook Promises an AI Revolution at Apple: "One of the Most Significant Technologies of Our Generation"
Are AI Data Centres the Infrastructure of the Future or the Next Crisis?
Miles Worth Billions: How Airlines Generate Huge Profits
Zelenskyy Returns to White House Flanked by European Allies as Trump Pressures Land-Swap Deal with Putin
Beijing is moving into gold and other assets, diversifying away from the dollar
Cristiano Ronaldo Makes Surprise Stop at New Hong Kong Museum
Zelenskyy to Visit Washington after Trump–Putin Summit Yields No Agreement
×