March 25, 2020

COVID-19 case-fatality rate, patient characteristics in Italy

By: Judy Mathias

Editor's Note

In the first half of February only three cases of COVID-19 were identified in Italy, and all had recently traveled to China. On February 20, a case of pneumonia due to SARS-CoV-2 was diagnosed in northern Italy’s Lombardy region. Within 14 days, many other cases of COVID-19 were diagnosed in the surrounding areas.

On the basis of the number of cases and the advanced stage of the disease, it was hypothesized that the virus had been circulating within the population since January. Since then, the number of cases has rapidly increased, mainly in northern Italy. The overall fatality rate, based on data up to March 17, was 1,625 deaths in 22,512 cases (7.2%).

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This rate is higher that in other countries (eg, 2.3% in China) and may be related to three factors:

  • 23% of the Italian population is aged 65 years or older, and COVID-19 is more lethal in older patients. When data were stratified by age group, the case-fatality rate in Italy and China were similar for age groups 0 to 69 years, but rates were higher in Italy in those aged 70 years or older (37.6% of cases in Italy, 11.9% in China) and similar for 80 years or older (21.9% in China, 20.2% in Italy). Patients 90 years or older in Italy (687 cases) had a very high fatality rate of 22.7%. This age was not reported in China.
  • Case fatality statistics in Italy are based on defining COVID-19-related deaths as those in patients who tested positive for SARS-CoV-2, independently from preexisting diseases that may have caused their deaths. Defining death from COVID-19 in this way may have resulted in an overestimation of the case-fatality rate. A subsample of patients with COVID-19 who died found: 117 patients (30%) had ischemic heart disease, 126 (35.5%) had diabetes, 72 (20.3%) had active cancer, 87 (24.5%) had atrial fibrillation, 24 (6.8%) had dementia, and 34 (9.6%) had a history of stroke.
  • After initially testing of both symptomatic and asymptomatic contacts of infected patients, on February 25, Italy issued more stringent testing policies that called for prioritized testing of patients with more severe clinical symptoms who were suspected of having COVID-19 and required hospitalization. Testing was limited for asymptomatic people or those with limited, mild symptoms. This strategy resulted in a high proportion of positive results of 19.3% and an apparent increase in the case-fatality rate because the more mild cases with low fatality rates were no longer counted in the denominator.

The findings highlight the need for transparency in reporting testing policies, with clear reporting of the denominators used to calculate case-fatality rates and the age, gender, and clinical comorbid status of affected persons, the authors say.


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