Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

The risk for death from COVID-19 is 1.38% overall, according to a new study. However, the fatality rate rises with age, from well below 1% among children aged 9 years or younger to nearly 8% for seniors aged 80 years or older, the latest statistics show.

"These early estimates give an indication of the fatality ratio across the spectrum of COVID-19 disease and show a strong age gradient in risk of death," write Robert Verity, PhD, from University College London, United Kingdom, and colleagues in a study published online in the Lancet Infectious Diseases.

Among those infected with SARS-CoV-2, the virus that causes COVID-19, the risk for hospitalization also increases with age. Specifically, 11.8% of people in their 60s require admission, as do 16.6% of people in their 70s and 18.4% for those in their 80s or older.

The case fatality estimates are based on data regarding individual patients who died from COVID-19 in Hubei, China, through February 8, as well as those who died in Hong Kong, Macau, and 37 countries outside China through February 25.

"It is clear from the data that have emerged from China that case fatality ratio increases substantially with age. Our results suggest a very low fatality ratio in those under the age of 20 years. As there are very few cases in this age group, it remains unclear whether this reflects a low risk of death or a difference in susceptibility, although early results indicate young people are not at lower risk of infection than adults," Verity and colleagues write.

The authors emphasize that serologic testing of adolescents and children will be vital to understanding how individuals younger than 20 years may be driving viral transmission.

In an accompanying editorial, Shigui Ruan, PhD, from the University of Miami in Coral Gables, Florida, writes that early detection, diagnosis, isolation, and treatment, as practiced in China, may help to prevent more deaths.

"Even though the fatality rate is low for younger people, it is very clear that any suggestion of COVID-19 being just like influenza is false: even for those aged 20–29 years, once infected with SARS-CoV-2, the mortality rate is 33 times higher than that from seasonal influenza," he writes.

Ruan, who uses applied mathematics to model disease transmission, notes that otherwise healthy people stand a good chance ― approximately 95% ― of surviving COVID-19, but the odds of survival for people with comorbidities will be "considerably decreased."

Time to Death or Discharge

Verity and colleagues first used data on deaths of 24 patients in mainland China and on 165 persons who recovered from infection outside of China to estimate the time between onset of symptoms and either death or discharge from the hospital. They estimated that the mean duration from symptom onset to death is 17.8 days, and the mean duration to discharge is 24.7 days.

They then estimated age-stratified case fatality ratios among all clinically diagnosed and laboratory-confirmed cases in mainland China to the end of the study period (70,117 cases).

The estimated crude case fatality ratio, adjusted for censoring, was 3.67%. With further adjustment for demographic characteristics and under-ascertainment, the authors' best estimate of a case fatality ratio in China is 1.38%.

The following figure shows adjusted fatality infection rates by age group.

The following figure shows adjusted fatality infection rates by age group.

The investigators note that the case fatality estimate is lower than the estimates for severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) outbreaks, both caused by coronaviruses, but "is substantially higher than estimates from the 2009 H1N1 influenza pandemic."

Earlier reports suggested that the overall fatality rate in China through February 11 was 2.3%. The rate in Hubei province, which is believed to be where the infection started, was 2.9%.

Hospitalizations Rise With Age

The investigators also estimated the proportion of infected patients who require hospitalization. Their estimation was based on data from a subset of cases reported in mainland China. The hospitalization estimates range from zero among the youngest patients to 18% among the oldest.

Table. Estimated Proportion of COVID-19 Hospitalizations by Age

Age Group in Years Proportion of Infected Patients Hospitalized (%) 0 – 9 0 10 – 19 .0408 20 – 29 1.04 30 – 39 3.43 40 – 49 4.25 50 – 59 8.16 60 – 69 11.8 70 – 79 16.6 80 or older 18.4

"Although China has succeeded in containing the disease spread for 2 months, such containment is unlikely to be achievable in most countries. Thus, much of the world will experience very large community epidemics of COVID-19 over the coming weeks and months. Our estimates of the underlying infection fatality ratio of this virus will inform assessments of health effects likely to be experienced in different countries, and thus decisions around appropriate mitigation policies to be adopted," Verity and colleagues conclude.

In his editorial, Ruan agrees with that assessment. "Although China seems to be out of the woods now, many other countries are facing tremendous pressure from the COVID-19 pandemic," Ruan writes. "The strategies of early detection, early diagnosis, early isolation, and early treatment that were practiced in China are likely to be not only useful in controlling the outbreak, but also contribute to decreasing the case fatality ratio of the disease."

The study was supported by the UK Medical Research Council. Verity and Ruan have disclosed no relevant financial relationships.

Lancet Infect Dis. Published online March 30, 2020. Full text, Editorial

Follow Medscape on Facebook, Twitter, Instagram, and YouTube.