At a news conference every evening, Jérôme Salomon, France’s director general of health, solemnly delivers an update on the state of the coronavirus epidemic in the country — just as public health officials around the world have been doing every day for weeks.

With each new tally of deaths and infections, news organizations and public health institutions like Johns Hopkins University in Maryland update their maps and charts depicting the pandemic’s severity and spread. The latest figures show that more than 13,000 people have died in Italy, the epicenter of the outbreak in Europe, followed by Spain and France. In the United States, the coronavirus has now killed more people than the Sept. 11 terrorist attacks.

Last week, however, Salomon’s terminology changed slightly. Rather than simply relaying the total number of deaths in France, as he had been doing, he specified that the daily tally reflected only deaths that had been recorded in hospitals.

The official figures “represent only a small part of deaths” in France, Salomon admitted. He acknowledged that “the two main places of death are the hospital and nursing homes.” A system for tallying deaths in nursing homes is planned for the coming days, but it is not yet operational.

“The absolute numbers would no doubt be effectively much higher if we aggregated what is happening in retirement homes, as well as the people who die at home or who are not counted,” Frederic Valletoux, president of the French Hospitals Federation, said last week.

Over the weekend, French Prime Minister Edouard Philippe acknowledged that concerns have been growing about the accuracy of the government’s coronavirus data.

“A lot of our fellow citizens are asking themselves questions about these figures, wanting to know how they are calculated, if they are comprehensive, which are fact and which are estimates,” Philippe said, adding that such questions were “warranted.”

The situation is similar in many countries — including the United States, where it has been difficult to obtain a complete picture of the scale of the epidemic. States and counties report their own figures, providing individual snapshots of the virus’s spread, and the Centers for Disease Control and Prevention tracks cases at the state level. Other organizations, such as Johns Hopkins, have attempted to provide more detailed counts by aggregating information from various sources, including federal, state, and local officials.

Even the most comprehensive tallies likely omit large numbers of people who may be sick but have not been tested for COVID-19, because tests are not available, their symptoms are too mild to qualify for a test, or they do not yet display any symptoms.

In Spain, as in France, deaths in retirement homes are also not included in the official statistics. According to the newspaper El Pais, however, at least 352 people have died from the coronavirus in nursing homes in Spain.

“It is plausible that deaths are underestimated,” Silvio Brusaferro, the president of Italy’s Higher Institute of Health, said this week. “We report deaths that are signaled with a positive swab. Many pneumonia-related deaths, presumably from COVID — for example in long-term care nursing homes — are not tested with a swab.”

Brusaferro said that public health officials in Italy were working to develop a more precise way to track the number of deaths in the country.

Last week, Angelo Borrelli, the head of Italy’s Civil Protection Service, suggested that the number of coronavirus infections also was far higher than the number officially reported. “A ratio of one certified case out of every 10 is credible,” Borrelli told la Repubblica.

Scientists and public health officials interviewed by HuffPost Italy agreed with Borrelli’s assessment, but cautioned against trying to come up with a specific estimate for the total number of cases.

“I mean, numbers are underestimated, but we don’t know the full extent at this time. It’s impossible to establish it with certainty,” Walter Ricciardi, a member of the World Health Organization and a scientific adviser to the Italian government, told HuffPost Italy.

THOMAS SAMSON via Getty Images French Prime Minister Edouard Philippe speaks, flanked by French Director General of Health Jerome Salomon, as he announces new measures to limit the spread of COVID-19, on March 14, 2020, in Paris.

In the United Kingdom, as well, hospital deaths have been the only coronavirus-related fatalities reflected in the official daily figures. This week, however, the government announced that it would begin publishing a weekly death toll based on registrations rather than just hospital reports. This means anyone who dies outside of a hospital will be included if a doctor or coroner, for example, notes COVID-19 as a factor in their death.

Even with improved reporting, however, the lack of widespread testing in many countries, combined with discrepancies in how infections are tallied, may make it difficult to truly understand the scale of the pandemic.

For example, in the U.K., the daily government figures on the number of infections indicate the results of tests as they come in, rather than the date when someone was tested because they were displaying symptoms of coronavirus.

This has led to large variations in the reported infection rates day to day that don’t reflect how the virus is actually spreading.

Sheila Bird, a biostatistician who previously worked for the Medical Research Council at the University of Cambridge, told HuffPost UK she believed the government should start reporting infection rates detected in hospital-based tests that reflect when samples were collected, rather than daily test outcomes, as this would give a far more accurate idea of the spread of the virus.

“It’s important that we know the sample week — not the week the test was reported, but the week the sample was taken from the patient,” Bird said. “It’s this date that characterizes the state of the epidemic.”

In the United States, it can take anywhere from 24 hours to 10 days to get the results of the test, depending on the lab and how backed up it is.

Adding to these challenges is the fact that scientists are learning more every day about how the coronavirus spreads. Recent studies in China and the U.S. suggest that a large number of infections are caused by people who display no symptoms of coronavirus.

On Tuesday, Robert Redfield, the director of the U.S. CDC, said in an interview with NPR that as many as one in four cases do not have symptoms.

“That’s important, because now you have individuals that may not have any symptoms that can contribute to transmission, and we have learned that in fact they do contribute to transmission,” Redfield said.

Additionally, Redfield said, the research suggests that people who do become symptomatic may be able to spread the virus up to 48 hours before they show symptoms.

“This helps explain how rapidly this virus continues to spread across the country,” he said.

With reporting from HuffPost France, HuffPost UK, HuffPost Spain, HuffPost Italy, and Reuters.