[ad_1]
The true number of COVID-19 infections is likely much higher than reported in many high-income nations around the world.
A recent estimate modeled by the United States, Australia, Canada, South Korea and 11 countries in Europe suggests that official figures may have a hard time capturing the full extent of the outbreak.
The new model from Australian scientists uses a “backcasting” method, which projects the number of new deaths per day in reverse, from the time of death to the time of infection. This allows scientists to avoid using epidemiological and serological data, which come with testing limitations.
By comparing the new estimates with the official confirmed cases, the team was able to predict the ‘real’ infection rate for each country. According to their findings, the population’s infection rate was, on average, six times higher than reported cases at the end of August.
“Unlike infections reported on the basis of RNA testing, backcasting does not depend on the coverage or effectiveness of testing regimes, which can be very different between jurisdictions and over time,” the authors write.
This means that it is much easier to use regionally, nationally or even internationally than other methods. Also, because it doesn’t rely on a nation that has widespread testing, it can help public health experts prepare in areas that have limited testing capabilities.
“In a nutshell, we analyzed statistics on how many people had died from COVID-19 in a given country and then worked backwards to see how many people would have had to be infected to get to that number of deaths,” says the data. scientist Steven Phipps from Ikigai Research in Australia.
“Our method is a new and easy-to-use method for estimating the true infection rate wherever reliable data is available on the number of deaths attributable to COVID-19.”
Some nations were better at reporting these infections than others. In South Korea, the actual number of infections was 2.6 times higher than the reported figures, while in Italy the number of “withdrawn” cases was surprisingly 17.5 times higher.
In general, since March, countries around the world have improved in introducing COVID-19 testing, educating the public about symptoms, and devising ever more accurate ways to detect and monitor infection.
Despite this improvement, international numbers continue to lag behind probable reality. Even in Australia, which has one of the best detection levels of all 15 countries studied, researchers say the infection rate may still be nearly five times higher than reported.
“We have found that COVID-19 infections are much higher than confirmed cases in many countries, and this has important implications for both control and probability of infection,” says Australian National University economist Quentin Grafton. .
“These findings raise serious questions about how we address all aspects of the coronavirus pandemic, including the ongoing morbidity and lifelong health impacts for people who have been infected, how we implement and manage blockages, and how we ensure we be on top of this pandemic more generally. “
This isn’t the first time scientists have found a discrepancy between actual COVID-19 cases and reported infections. Practically from the start, experts have warned that we will likely underestimate the true extent of the viral spread.
Determining a cause of death from the novel coronavirus isn’t easy when tests are limited, symptoms often overlap with other diseases, and those who are most vulnerable have pre-existing medical conditions.
Many estimates to date have either compared the total mortality rate in 2020 with what it would have usually been in another given year, or used antibody tests to go back and identify individuals who were not included in the initial case figures. probably because they showed little or no symptoms.
Most epidemiological models agree that actual infections far outweigh confirmed cases, but exactly how much and how they change over time is less clear.
Epidemiological data is limited by a nation’s test level, and the antibody test comes with some false positives and false negatives, meaning that if the number of cases is low, population-wide even a handful of false results can distort the data.
An estimate from another study in the United States found that the number of infections in April was 3 to 20 times higher than the number of confirmed cases, and most of this was due to incomplete testing and, to a lesser extent, accuracy. of the imperfect test.
Another estimate based on antibody data in the United States found there were 10 times more SARS-CoV-2 infections than those reported in May.
The new model relies only on high-income countries that have relatively widespread testing regimes. Most nations, however, have carried out far fewer tests among their populations, which suggests that the number of people globally who have been infected with COVID-19 is likely many times higher than official figures.
Some countries such as Belgium, France, Italy and the UK showed very low real detection rates. As of August 31, 2020, official data in these nations represented only 10% of all actual COVID-19 cases, according to the new analysis.
At this point, however, no estimates are perfect and this new method should not replace the existing ones, it should simply complement them.
Epidemiological models are still much better at predicting future hospitalizations than backcasting methods, and the authors fully admit this.
It is also important to note that for the backcasting to be accurate, the age distribution among people infected with COVID-19 must be broadly similar, because older people have a higher chance of dying once infected. This could skew outcomes in places like Australia, where around 75% of deaths occurred while aged care.
Finding the best way to estimate past, current and future COVID-19 cases will take time and, to some extent, it may be impossible to know exactly how many people will be sick from the current pandemic.
That said, accurate estimates of the true burden of COVID-19 will be crucial in determining how to respond to the global tragedy in our hands.
The study was published in Royal Society Open Science.
.
[ad_2]
Source link
