A new paper by the Chinese Centers for Disease Control and Prevention (CCDC) finds that the majority of coronavirus cases are mild, with older adults and people who have other conditions being most at risk.

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Wearing face masks, handwashing, and other protective measures may have helped the coronavirus outbreak slow, suggests new research.

CCDC’s Novel Coronavirus Pneumonia Emergency Response Epidemiology Team has conducted a study wherein they analyze all the confirmed coronavirus cases, as of February 11, 2020.

Experts have recently named the novel coronavirus SARS-CoV-2. The disease that infection with the virus causes is called COVID-19.

In the new study, the CCDC team extracted all the COVID-19 cases that China’s Infectious Disease Information System had recorded.

In their analysis, the scientists included the following:

  • a “summary of patient characteristics”
  • an analysis of viral spread by age and sex
  • a calculation of deaths and the “case fatality rate
  • an analysis of viral spread over time and geographical space
  • an epidemiological curve, or visual display of the outbreak
  • a subgroup analysis of cases outside of China’s Hubei Province and “all cases among health workers nationwide”

The findings appear in the journal CCDC Weekly.

The researchers analyzed a total of 72,314 patient records, which included: “44,672 (61.8%) confirmed cases, 16,186 (22.4%) suspected cases, 10,567 (14.6%) clinically diagnosed cases,” and “889 asymptomatic cases (1.2%).”

Of the total number of individuals with confirmed cases, 80.9% were said to be “mild.” Most of the adults affected were between 30 and 79 years old.

Of the total number of confirmed cases, there were 1,023 fatalities, the equivalent of a death rate of 2.3%. The virus proved more fatal for men — 2.8% — than women — 1.7%.

Importantly, the study found that the case fatality rate rises with age. Specifically, up to the age of 39 years old, the fatality rate is 0.2%, at the age of 40, it is 0.4%, 1.3% for those in their 50s, 3.6% for people in their 60s, and finally, 8% for those in their 70s.

By comparison, the Severe Acute Respiratory Syndrome (SARS) that health experts have likened coronavirus to affected fewer people in 2002–2003, but the death rate was 14–15%, according to the World Health Organization (WHO).

In terms of the geotemporal spread of the virus, the study confirms that “COVID-19 spread outward from Hubei Province sometime after December 2019, and by February 11, 2020, 1,386 counties across all 31 provinces were affected.”

The study also found that people with cardiovascular disease were at the highest risk of death from coronavirus, followed by those with diabetes, chronic respiratory disease, hypertension, and cancer.

Furthermore, the authors note a “downward trend in the overall epidemic curve.”

The epidemic curve showed that the onset of symptoms “peaked around January 23–26, then began to decline, leading up to February 11,” they write.

They add that this suggests “that perhaps isolation of whole cities, broadcast of critical information (e.g., promoting handwashing, mask wearing, and care seeking) with high frequency through multiple channels, and mobilization of [a] multi-sector rapid response teams is helping to curb the epidemic.”

However, the authors caution that a “rebound” of the epidemic is still very much possible:

“[The] COVID-19 epidemic has spread very quickly, taking only 30 days to expand from Hubei to the rest of Mainland China. With many people returning from a long holiday, China needs to prepare for the possible rebound of the epidemic.”

The study also found that “A total of 1,716 health workers have become infected and 5 have died (0.3%).”

However, “The percentage of severe cases among Wuhan medical staff has gradually decreased from 38.9% at the peak (on January 28) to 12.7% in early February.”