Add news
March 2010
April 2010
May 2010June 2010July 2010
August 2010
September 2010October 2010
November 2010
December 2010
January 2011
February 2011March 2011April 2011May 2011June 2011July 2011August 2011September 2011October 2011November 2011December 2011January 2012February 2012March 2012April 2012May 2012June 2012July 2012August 2012September 2012October 2012November 2012December 2012January 2013February 2013March 2013April 2013May 2013June 2013July 2013August 2013September 2013October 2013November 2013December 2013January 2014February 2014March 2014April 2014May 2014June 2014July 2014August 2014September 2014October 2014November 2014December 2014January 2015February 2015March 2015April 2015May 2015June 2015July 2015August 2015September 2015October 2015November 2015December 2015January 2016February 2016March 2016April 2016May 2016June 2016July 2016August 2016September 2016October 2016November 2016December 2016January 2017February 2017March 2017April 2017May 2017June 2017July 2017August 2017September 2017October 2017November 2017December 2017January 2018February 2018March 2018April 2018May 2018June 2018July 2018August 2018September 2018October 2018November 2018December 2018January 2019February 2019March 2019April 2019May 2019June 2019July 2019August 2019September 2019October 2019November 2019December 2019January 2020February 2020March 2020April 2020May 2020June 2020July 2020August 2020September 2020October 2020November 2020December 2020
News Every Day |

Just how many people really have (and have had) COVID-19?

New research published today shows that the number of cases of COVID-19 are much greater than reported, and this has important implications about how we respond to the pandemic crisis, Quentin Grafton, Steven Phipps, and Tom Kompas write.

A peer reviewed manuscript published in the respected journal Royal Society Open Science today shows that in some countries, COVID-19 case numbers may be up to 17 times greater than those confirmed by testing.

According to John Hopkins University and the World Health Organization (WHO), as of 17 November, the global number of total cases – that is, all recovered, active, and fatal cases combined – was 55 million. Total deaths were 1.3 million, and the number of confirmed cases was increasing by about half a million per day.

Confirmed cases are the number of persons who have tested positive for RNA material of SARS-CoV-2 (the virus that causes COVID-19) present in their nasal secretions or sputum. As a complement to RNA testing, and to estimate the true infection rate, researchers have also undertaken seroprevalence studies that test for antibodies in blood samples. Identification of antibodies in the blood can indicate that a person either has or has recovered from COVID-19.

Seroprevalence studies need to be repeated regularly and be based on an appropriately stratified random sample of the population to obtain a reasonable estimate of the true (population) infection rate.

A challenge with seroprevalence studies is that, if the true rate of infection is relatively low (say one per cent or less), then the number of false positives or false negatives may make the sero-surveys unreliable as a means of estimating true infection rates.

This is true even if the sero-test has a high proportion of true positives and true negatives.

More on this: The coronavirus crisis: how did we get here, and what should we do next?

To combat this difficulty, we employed a statistical method called backcasting that allows us to obtain estimates of the true infection rate based on a range of infection fatality rates (0.37 to 1.15 per cent) and the time from infection to symptoms (4.1 to 7.0 days) and time from symptoms to death (12.8 to 19.2 days).

Using our method, we generated multiple random values based on the range of possible values of these three parameters (infection fatality rate, time to symptoms and time to death) to provide a 95 per cent confidence interval around our estimates of the true infection rate.

Our analysis covered 15 developed countries with a combined population of over 800 million people. Our backcasting method generated similar results to national seroprevalence studies. Importantly, we found that COVID-19 is far more prevalent than is suggested by reported statistics of confirmed cases identified by RNA tests.

We found that the true number of infections across our sample of 15 developed countries is 6.2 times greater (95 per cent confidence interval: 4.3–10.9) than the number of cases confirmed by RNA testing. We also found a strong negative relationship between the proportion of people testing positive for the virus from RNA testing and the detection rate of COVID-19 in the population.

Our method is novel and easy-to-use and especially valuable wherever there is reliable data on the number of fatalities attributable to COVID-19. Unlike reported infections based on RNA tests, backcasting is not dependent on the coverage or efficacy of testing regimes.

Backcasting is also scalable to a local, regional or national level, can be readily updated on a daily basis using data that has already been reported, and makes no assumptions with regard to how the number of COVID-19 infections has evolved over time.

More on this: Podcast: The future of healthcare and the fight against COVID-19

Our approach is particularly advantageous in locations where there is little testing or limited capacity to forecast rates of infection but where there is a need, for the purposes of public health planning, for a more accurate population-level measure of COVID-19 infection.

While our method is robust, we highlight three limitations when comparing infection rates across countries and over time.

First, the age distribution across different populations needs to be broadly similar, because the infection fatality rate from COVID-19 is highly dependent on age.

Second, the level of medical care across countries should also be comparable, because COVID-19 fatalities depend on access to medical services, such as the use of ventilators.

Third, the infection fatality rate should be broadly constant over time, as any substantial change may introduce biases into the estimated population infection rates.

Most countries in the world have undertaken fewer tests per 1,000 people than the 15 countries considered in this research, and also have a lower capacity to test for COVID-19. This suggests that globally the number of people who are infected with, or who have recovered from COVID-19, is many times greater than the reported number of cases from viral testing.

Even within our sample, the countries with the lowest detection rates (Belgium, France, Italy, and the United Kingdom) appear to have a population infection rate that could be up to 17 times greater (Italy)  than reported by confirmed cases via John Hopkins University or the WHO.

While there are many ways to respond to COVID-19, our statistical measures of the true infection rate should promote better public health decision-making. This is important because if governments do not know how many people have been infected in a population, it becomes very hard to plan a pandemic response effectively.

The post Just how many people really have (and have had) COVID-19? appeared first on Policy Forum.

Read also

Bryan Quinby, Singing “The Birthday Song” at Chuck E. Cheese

HIV medication will soon be available in a strawberry-flavored, dissolvable tablet for kids

A first look at Ohio’s initial COVID-19 vaccine distribution plan

News, articles, comments, with a minute-by-minute update, now on — latest news 24/7. You can add your news instantly now — here