As Russia’s surging corona virus infections have turned it into a global epidemic hot spot second only to the U.S., one thing puzzles health experts: Why is it reporting so few deaths?

Russian officials say 2,212 people have died so far from Covid-19 out of 242,271 confirmed cases since the epidemic erupted. Russia’s total cases on Tuesday overtook those of Spain, which has reported close to 27,000 deaths, after passing the U.K. and Italy, which have more than 12 times the Russian level of fatalities.

The World Health Organization said it’s in talks with Russia about the country’s statistics for corona virus deaths, which at 0.9% is far below the global average and the lowest among nations with the highest numbers of infections.

“We as the WHO are closely discussing this with the Russian authorities,” Melita Vujnovic, the organization’s chief representative in Russia, said in a phone interview last week. “They are looking at the entire mortality to see if something has been missed.” The Health Ministry didn’t respond to requests for comment for this article.

The Geneva-based agency of the United Nations issued guidelines in mid-April asking countries to register fatalities linked to Covid-19 “where the disease caused, or is assumed to have caused, or contributed to death.” Data from four Russian regions, though, suggest deaths may be far higher when cases are counted in which patients diagnosed with the illness died of other conditions such as liver or heart failure.

The mortality rate is low in Russia because the statistics only include the deaths of people directly attributed to Covid-19, said an official with knowledge of corona virus fatality calculations. Other countries with higher totals have broader criteria for attributing deaths to the virus.

Russian Deputy Prime Minister Tatyana Golikova Tuesday rejected suggestions Russia was understating the death rate. “That’s what it is and we never manipulate official data,” she said.

The Health Ministry said Wednesday that it follows international statistical rules in classifying deaths of people diagnosed with Covid-19. This means listing as the cause of death the condition that led to it such as acute vascular failure, the ministry said in a statement to the state-run Tass news service.

Some regions are starting to list deaths of patients who tested positive for corona virus as well as those of people that doctors considered were killed by the pathogen.

Russia has reported record levels of infections averaging more than 10,000 new cases per day since May 3, even as the country was placed under a nationwide stay-at-home order at the end of March that helped trigger a slump in economic activity. Amid fears Russia may be sliding into a deep recession, President Vladimir Putin announced the end of the lock down on Monday, while making regional leaders responsible for deciding the pace of safely easing the measures in their areas.

Even as its infections have accelerated, Russia remains the only one of the 10 most-affected nations with a death rate below 1%. Spain, France and the U.K. have mortality rates among those confirmed to have corona virus ranging from 12% to 14%, while the U.S. comes in at 6% and Germany at 4.4%. Globally, out of 4.3 million known infections, 293,366, or 6.8%, have died.

To be sure, a massive increase in testing in Russia has led to a large number of reported new infections, more than 40% of which display no symptoms. Still, in South Korea, which has one of the most extensive systems for tracking corona virus, the death rate is 2 1/2 times higher than the Russian one.

Russia’s Urals region of Chelyabinsk stands out for the transparency of its Covid-19 data, breaking down deaths between those immediately caused by the virus — four — and ones that occurred with people who were infected but died from other conditions — eight. Only the four deaths are recorded for Chelyabinsk in national statistics.

Perm, also in the Urals, has reported 23 deaths versus 12 attributed to the region by the authorities in Moscow. Ryazan in central Russia has recorded 15 deaths among people either diagnosed with Covid-19 or suspected of having the disease, whereas the national database shows seven fatalities. Saratov in Russia’s south west has compiled a list of 17 corona virus-related deaths compared to five for the region in the nationwide data.

Differences in monthly average death registrations also point potentially to a higher mortality rate in Russia from the corona virus. The total number of deaths in Moscow in April was 1,854 higher than the average for that month since 2010.

At a news briefing on Tuesday, Golikova rejected suggestions the excess-death data indicate Russia is understating deaths from Covid-19.

Russia’s death rate is “dramatically low on the world stage,” Jeremy Rossman, a senior lecturer in virology at the University of Kent in the U.K., said in a phone interview. “It’s implying that the risk of death from Covid-19 is lower than it in fact is. Being open in terms of reporting is really important because we need to understand the range of fatalities occurring.” – Bloomberg