Huge asymptomatic pool of coronavirus infected worldwide, say researchers

A startling new report from the University of Göttingen debunks the idea that the official statistics regarding the number of confirmed cases of the pandemic COVID-19 are accurate. It is much more likely, say the researchers, that the official figures which are the basis of government action and of much media analysis represent only about 6% of all infections. If so, they say, there are already tens of millions of infected people worldwide.

Image Credit: Corona Borealis Studio / Shutterstock
Image Credit: Corona Borealis Studio / Shutterstock

The estimates

First reported in Wuhan, China, the COVID-19 pandemic has fanned out to over 200 countries, until on February 26, the rest of the world was reporting more cases than China. As of today, April 8, 2020, there are over 1.43 million cases and 82,119 deaths due to COVID-19 illness reported globally.

Using estimation methods derived from an earlier study published in The Lancet Infectious Diseases, the investigators estimate that on the same date, there were actually about 460,000 infections instead of the 71,000 reported in Germany alone. Today Germany is reporting 107,663 confirmed cases. Using the same estimation technique, the US would have about 10 million and Spain over five million. Other front-runners include Italy with around 3 million and the UK with around 2 million. But John Hopkins University reports put the total count of confirmed cases today at 1,431,375 – the inevitable conclusion is that most infections are going undiscovered.

The study is based on the estimates of mortality and time until death reported in the recent The Lancet study. The researchers explain why some European countries, like Europe and Spain, have a much higher number of deaths in comparison to the number of confirmed infections, than Germany. The reasons boil down to inadequate testing carried out too late to control the spread of infection.

South Korea and Taiwan have led the testing field almost from the beginning, with almost half of all infections with this virus having been detected so far. On the other hand, the US and the UK have been criticized by numerous public health specialists for failing to take lockdown and other proven preventive measures in time despite the adequate warning. Their failure to prepare for the pandemic and stockpile testing kits and medical or protective equipment is hurting them immensely at present.

Germany has a highly impressive testing rate, with over 15.5% of infections being detected. This is in contrast to the 3.5% detection rate in Italy, 1.7% in Spain, the UK’s 1.2% and 1.6% in the US.

Pompano Beach, Florida/USA - March 20, 2020: Coronavirus (COVID-19) Drive-thru testing spot. Image Credit: YES Market Media / Shutterstock
Pompano Beach, Florida/USA - March 20, 2020: Coronavirus (COVID-19) Drive-thru testing spot. Image Credit: YES Market Media / Shutterstock

How do case fatality estimates go wrong?

The researchers point out a number of errors that can bias the estimates of case fatality (the number of deaths divided by the number of laboratory-confirmed cases) during the early part of an epidemic. Firstly, the lag between the onset of symptoms, detection of the case, reporting, and the recording of the final outcome means that in the growth phase, many, if not most, outcomes remain unknown. This drives down the actual fatality rate at this point. The lag between the first symptom and recovery is also a factor in this effect.

Severe cases are detected more often than mild ones, driving up the case fatality ratio during this time, however. To correct for all of these biases, the researchers in The Lancet study adjusted their estimates of the case fatality ratio to arrive at more reliable numbers, which would help to plan public health interventions better until definitive data is available.

Current estimates

Based on these methods, the researchers estimate an overall case fatality ratio of 1.4%, which is much lower than the crude case fatality ratio from China of 3.7%. The latter is higher because it “does not take into account the severity of cases.” Considering the number of infections in proportion to the risk of death, the infection fatality ratio is 0.66% in China overall. Still, the infection rate is significantly rising among the elderly, above 50 years of age.

Though the value of 1.4% is much lower than for the past SARS and MERS epidemics, it is higher than the estimated case fatality ratio for the H1N1 flu epidemic in 2001. It will vary with the type of patient assessed (severe symptomatic vs. mild unreported cases). Moreover, in those aged less than 60 years, it is 0.32% vs. 6.4% in those aged 60 or more, to 13% in those who are 80 years old or more.

What does the study mean?

According to researcher Sebastian Vollmer, these results should be a wake-up call to governments all around the world. The current officially reported statistics simply don’t cut it when it comes to providing a platform for planning future preventive measures. “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.”

The study means that countries urgently need to upgrade their detection of new cases in order to effectively execute containment measures. Blood testing will be essential to understand, for instance, what role the young play in disease spread among the community.

Dr. Liji Thomas

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.


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