The Covid-19 pandemic has caused nearly 6.9 million deaths across the world, more than double the number officially recorded, a new analysis from the University of Washington's Institute for Health Metrics and Evaluation (IHME) estimated.
Deaths go unreported as most countries only record those that occur in hospitals or of patients with confirmed infection, the report showed.
The IHME is an independent health research organisation that provides comparable measurement of the world's health problems and has been cited in the past by the White House and its reports are watched closely by public health officials.
The reported Covid-19 mortality is strongly related to the levels of testing in a country, the IHME said.
"If you don't test very much, you're most likely to miss Covid deaths," Christopher Murray, director of the Institute for Health Metrics and Evaluation, said in a briefing call with journalists.
IHME estimated total Covid-19 deaths by comparing anticipated deaths from all causes based on pre-pandemic trends with the actual number of all deaths caused during the pandemic.
In the United States, the analysis estimated Covid-19 related deaths of more than 905,000. Official figures from the US Centres for Disease Control and Prevention on Wednesday estimated 575,491 deaths due to the novel coronavirus.
The CDC did not immediately respond to a Reuters request for comment on the report.
The report only includes deaths caused directly by the virus, not deaths caused by the pandemic's disruption to healthcare systems and communities.
"Many countries have devoted exceptional effort to measuring the pandemic's toll, but our analysis shows how difficult it is to accurately track a new and rapidly spreading infectious disease," Murray said.