Wednesday, February 19, 2020

A Statistical Analysis of COVID-19

recently released study of the COVID-19 virus by the Chinese Center for Disease Control and Prevention provides us with a fascinating analysis of the world's latest coronavirus, in particular, a statistical analysis of which groups of people have been impacted the most.

The study entitled "Vital Surveillances: The Epidemiological Characteristics of an Outbreak of the 2019 Novel Coronavirus Diseases (COVID-19) - China, 2020" used data current through February 11, 2020.  The authors of the study looked at a total of 72,314 patient records of which 44,672 (61.8 percent) were confirmed cases, 16,186 (22.4 percent) suspected cases, 10,567 (14.6 percent clinically diagnosed cases in Hubei Province) and 889 (1.2 percent) asymptomatic cases.  Information that would have identified the patients were stripped from records and there was no sampling done to achieve a predetermined study size since all cases were included in the study.

The severity of symptoms was categorized as follows:

1.) Mild - non-pneumonia and mild pneumonia cases

2.) Severe - dyspnea (shortness of breath), respiration frequency greater than 30 per minute, blood oxygen saturation less than 93 percent and/or lung infiltrates greater than 50 percent within 24 to 48 hours.

3.) Critical - respiratory failure, septic shock, multiple organ dysfunction or failure.  

Confirmed cases were based on positive viral nucleic acid tests on throat swabs.  Clinically diagnosed cases were suspected cases with lung imaging features consistent with coronavirus pneumonia.   Asymptomatic cases were diagnosed based on positive viral nucleic acid test results but an absence of COVID-19 symptoms such as fever and dry cough.

Let's open with this series of maps showing how COVID-19 spread throughout China:

Here is what the authors found:

1.) The fatality rate of 2.3 percent was found among confirmed cases (1,023 deaths out of 44,672 confirmed cases).

2.) The fatality rate was highest among patients aged 80 and older at 14.8 percent

3.) The case fatality rate for males was 2.8 percent.

4.) The case fatality rate for females was 1.7 percent.

5.) Patients who reported being retired had the highest fatality rate at 5.1 percent.

6.) The fatality rate in Hubei Province was 2.9 percent compared to only 0.4 percent fatality rate in other provinces.

7.) Patients with no pre-existing or comorbid condition (simultaneous health conditions) had a fatality rate of 0.9 percent.

8.) Patients with a comorbid condition had a mortality rate that was much higher as follows:

a.) cardiovascular disease - 10.5 percent

b.) diabetes - 7.3 percent

c.) chronic respiratory disease - 6.3 percent

d.) hypertension - 6.0 percent

e.) cancer - 5.6 percent

9.) Case fatality rate for cases categorized as critical was 49 percent.

10.) No deaths have occurred among cases classified with mild or severe symptoms.

Here is a table which summarizes the findings of the study:

Let's close with a final quote from the authors:

"In conclusion, the present descriptive, exploratory analysis of the first 72,314 cases of COVID-19 reported through February 11, 2020 offers important new information to the international community on the epidemic in China. In particular, this analysis chronicles the extremely rapid spread of the novel coronavirus despite extreme efforts to contain it. However, important questions remain including identification of the animal reservoir, determination of infectiousness period, identification of transmission routes, and effective treatment and prevention methods including further test development, drug development, and vaccine development. As an international community, we must all be responsible partners in surveillance, communication, response, research, and implementation of evidence-based public health and clinical practice. The massive vigorous actions taken by the Chinese government have slowed down the epidemic in China and curbed spread to the rest of the world. Although the epidemic appears to be in decline in the lead up to February 11, 2020, we may yet face more challenges. Huge numbers of people will soon be returning to work and school after the extended New Year holiday. We need to prepare for a possible rebound of the COVID-19 epidemic in the coming weeks and months."

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