Chinese CDC study finds Covid-19 virus to be more contagious than SARS or MERS

A comprehensive study of more than 72,000 confirmed and suspected cases of the novel coronavirus by Chinese scientists has revealed new information about the deadly infection which has brought much of the country to a halt.

Carried out by a group of experts at the Chinese Center for Disease Control and Prevention and published in the Chinese Journal of Epidemiology on Monday, the study is the largest and most comprehensive examination of coronavirus cases so far.

It found that the novel coronavirus is more contagious than the related viruses which cause SARS and MERS. While the resulting disease, Covid-19, is not as fatal on a case-by-case basis, its greater spread has already led to more deaths than its related coronaviruses.

The new study examined data from 72,314 patients, 44,672 of which were confirmed cases of the virus (61.8%), along with 10,567 clinically diagnosed cases (14.6%) and 16,186 suspected cases (22.4%). An additional 889 cases examined did not show any symptoms.

"Clinically diagnosed cases," are patients who demonstrate all the symptoms of Covid-19 but have either not been able to get a test or are believed to have falsely tested negative.

Of the 44,672 confirmed cases, the Chinese CDC said there were 1,023 deaths, a crude mortality rate of 2.3%, which is in line with other studies and projections. By comparison, SARS had a mortality rate of 9.6% during the 2003 outbreak, while MERS has a case fatality of 35%. Seasonal influenza, which is highly contagious and effects tens of millions of people, has a mortality rate of around 0.1%, according to the most recent estimates from the US Centers for Disease Control.

International experts have cautioned that early numbers may not tell the whole story. Case fatality rates may come down as officials discover milder cases who don't seek medical care.

"My sense and the sense of many of my colleagues, is that the ultimate case fatality rate ... is less than 2%," Dr. Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, told CNN's Jim Sciutto on "New Day" Tuesday. "What is likely not getting counted is a large number of people who are either asymptomatic or minimally symptomatic, so the denominator of your equation is likely much much larger."

"So I would think at tops it's 2% and it likely will go down when all the counting gets done to 1% or less. That's still considerable if you look at the possibility that you're dealing with a global pandemic," he added.

Because the Covid-19 virus has infected far more people than the viruses that caused SARS and MERS, the number of people who have died from it so far has already overtaken both viruses. The SARS outbreak claimed the lives of 774 people, while MERS has killed at least 828 people since 2012.

Even so, flu has led to far more deaths than all of these viruses combined -- killing tens of thousands of people in the US each year -- due to its massive spread.

The latest death toll from Covid-19 is over 1,800, all but five of which occurred in mainland China, where the worst of the outbreak is centered.

Many of those deaths have been among older people and those with preexisting conditions that make them more susceptible to serious illness from viral infections. The Chinese CDC study found that among patients aged 80 and above, the crude fatality rate is 14.8%. Among those with pre-existing conditions, those with cardiovascular disease were found to be most at risk, with a fatality rate of 10.5%.

The contagious nature of the virus has also put medical workers at risk -- as of February 11, more than 3,000 hospital staff or other medics had been reported to have been infected with the virus, among whom 1,716 had been confirmed by nucleic acid tests. Of the confirmed cases, only a small number has resulted in death -- roughly 0.3%, according to the authors.

Release of the study comes as Chinese officials were hailing what seemed to be the turning of a corner in the fight against the virus. Outside of Hubei province, the epicenter of the outbreak, the number of new cases reported has fallen for the past 14-days.

However, scientists previously warned of self-sustaining epidemics in Chinese cities, and both Beijing and Shanghai remain on tight lockdown to guard against the virus' spread.

While the number of new reported cases have gone down in China and some other countries, the World Health Organization (WHO) has warned that new data must be analyzed "cautiously."

"This trend must be interpreted very cautiously. Trends can change as new populations are affected. It's too early to tell if this reported decline will continue. Every scenario is still on the table," Tedros Adhanom Ghebreyesus, director-general of WHO, said during a press conference Monday.

Tedros added that more than 80% of patients "have mild disease and will recover."

"In about 14% of cases, the virus causes severe diseases including pneumonia and shortness of breath. And about 5% of patients have critical diseases including respiratory failure, septic shock and multiorgan failure," he said. "In 2% of reported cases, the virus is fatal, and the risk of death increases the older you are. We see relatively few cases among children. More research is needed to understand why."