LONDON - Public health officials and epidemiologists are at odds over how deadly COVID-19 will prove to be, with forecasts ranging from 1% to 3.4% of infected people dying.
The disparity, disease modelers and virologists say, isn't surprising for a novel virus. They warn national differences could skew predictions — especially if health care systems are overwhelmed by patients needing hospitalization and buckle under the strain.
Some epidemiologists worry that may be happening now in the worst affected parts of northern Italy. The death-to-case ratio in Italy climbed Sunday to an alarming 5%, with the Civil Protection Agency reporting a disturbing 51% spike in deaths, bringing the total death toll attributed to coronavirus to 366.
Italy's spike in mortalities exceeded worst-case forecasts, as well as the overall rate in other stricken countries. But public health officials say the death toll is not extraordinary considering Italy has a large elderly population with nearly a quarter of Italians over 65. Only Japan has an older demographic among advanced countries. China has seen about 9% of over-80-year-old coronavirus victims die. In Italy, the death rate for infected seniors is just over 8%.
As of Monday, Italian authorities reported only two deaths under the age of 63, and said that many who succumbed to the virus were in their 80s or 90s. Most already had weakened immune systems from chronic health conditions, including kidney disease, diabetes and heart problems.
Nonetheless, public health officials say that while the health care system is holding up, it is under extraordinary strain that will likely worsen if drastic containment measures announced Sunday by Prime Minister Giuseppe Conte don't start having an effect.
Italy is taking unprecedented steps to handle the patients needing hospitalization by bringing doctors out of retirement and accelerating graduation dates for nursing students. Lombardy, the worst affected Italian region, already has more than 10% of its doctors and nurses unable to work because they tested positive for the virus and are in quarantine, according to the Lombardy region's top health official, Giulio Gallera.
Hospitals in the towns of Lodi and Cremona last week were so packed that they had to shutter their emergency rooms and send patients elsewhere.
"Some of the hospitals in Lombardy are under a stress that is much heavier than what this area can support," Dr. Massimo Galli, head of infectious disease at Milan's Sacco Hospital, told Sky TG24. "This epidemic is on a scale that is larger than anyone could have thought, imagined or prevented."
More than 300 triage tents have been erected outside medical facilities to handle the volume.
Italy aside, the disparity in death-toll forecasts sparked a political dispute in the U.S. last week when U.S. President Donald Trump speculated the death-to-case ration will end up at around 1%, contradicting the World Health Organization (WHO), which has pegged the global mortality rate for the coronavirus at around 3.4%.
"Well, I think the 3.4% is really a false number. Now — and this is just my hunch — but based on a lot of conversations with a lot of people that do this. Because a lot people will have this, and it's very mild. They'll get better very rapidly. They don't even see a doctor. They don't even call a doctor," Trump said during a television interview.
British medical officials say they also suspect the mortality rate of the virus will be about 1%. Chris Whitty, the country's top medical officer, told lawmakers last week it was heartened by the decline in cases in China and the slowing death rate there.
Epidemiologists and disease modelers are united on one thing — they all acknowledge that forecasting the case fatality ratio is highly tricky because of unknown variables. Not everything is understood about the novel virus, and trying to adjust for undetected or unreported cases is also a challenge. Refined treatment protocols and the use of repurposed existing drugs could alter the picture significantly, they say.
"It is surprisingly difficult to calculate the death rate during an epidemic," said John Edmunds, a professor in the Center for the Mathematical Modeling of Infectious Diseases, at the London School of Hygiene & Tropical Medicine. "This is because it takes some time to die. In the case of COVID-19, the time between onset of the disease and death is quite long — two to three weeks or more— so the number of cases that you should divide by is not the number of cases that we have seen to this point, but the number of cases that there were a few weeks ago. Estimating what fraction of the cases might be reported is very tricky."
He noted that not all cases of infection will be reported, because only mild symptoms are suffered.
"If there are many more cases in reality, then the case-fatality ratio will be lower," he told the Science Media Center website.
And there are other factors that can upset predictions, including people's adherence to or disregard of protocols like self-isolation and handwashing. The efficacy of the containment and delay strategies governments craft and implement to retard the spread of the disease will also be critical.
Avoiding significant infection spikes will be crucial — high volumes of patients needing hospitalization at the same time can overwhelm health care services, leading to a shortage of beds or attending staff. The end result can be inadequate treatment and more deaths.
While Italy, with its soaring numbers of infections, is focusing on what Conte described Monday as "shock therapy" with a Chinese-like containment policy, British virologists and epidemiologists are advising Downing Street to pursue a much more phased approach, arguing that timing is everything. They worry a draconian containment policy may help now but could set the stage for a large second wave of contagion later in the year.
The British hope to avoid large numbers of people in hospitals at the same time. Disease modeling by the Statistics and Epidemiology Department at Britain's Lancaster University, which is advising Downing Street, suggests an extreme approach like China's quarantining of Hubei province, where the virus first appeared, initially can be highly effective, but that when measures are relaxed, a higher peak subsequently emerges, according to Britain's Sky News.
"One of the things which is clear, if you model out the epidemic, is you will get 50% of all the cases over a three-week period, and 95% of the cases over a nine-week period, if it follows the trajectory we think it's likely to," Whitty told British parliamentarians last week.
He said his aim is to try to space out the cases, making it easier for Britain's public National Health Service, the NHS, to manage them.