#disease #biology


COVID-19 is a disease caused by the SARS-CoV-2, a coronavirus. It caused a pandemic in 2020, and its death rate is between .5 and 3%.

Symptoms of the COVID-19 are flu-like: fever, cough and shortness of breath, and on average develop within 5 days from exposure[2]-[7]. It may be asymptomatic, most of the cases present mild symptoms[5].

Infection is typically spread through droplets from nose and mouth (e.g. coughing, exhaling and sneezing) contaminating surfaces than people through . Studies suggest that it does not transmit by air, and the risk of catching it from someone with no symptom is very low[1]-[2].

Mainly people over 30 are getting infected, children have very little chance[4], higher chance for blood group A and lower for O[3].

Unlike the flu, SARS-CoV-2, as an unsegmented virus, is relatively stable ; which means that differences betweens mutations are minor and immunity to one will likely confer immunity to all strains. This makes the likelihood of a vaccine relatively high[6]. There is only one strain of the virus as of may 2020[8].



[1]: CDC/Covid-19 transmission

[2]: WHO / Q&A on COVID-19.

[3]: Jiao Zaho / Relationship between the ABO Blood Group and the COVID-19 Susceptibility

> Meta-analyses on the pooled data showed that **blood group A had a significantly higher risk** for COVID-19 (odds ratio-OR, 1.20; 95% confidence interval-CI 1.02~1.43, P = 0.02) compared with non-A blood groups, whereas blood **group O had a significantly lower risk** for the infectious disease (OR, 0.67; 95% CI 0.60~0.75, P < 0.001) compared with non-O blood groups
> ~ Jiao Zaho, Relationship between the ABO Blood Group and the COVID-19 Susceptibility

[4]: Zunyou Wu, MD, PhD1; Jennifer M. McGoogan, PhD1 / Summary of a Report of 72 314 Cases From the Chinese Center for Disease Control and Prevention

> Age distribution (N = 44 672)
> ≥80 years: 3% (1408 cases)
> 30-79 years: 87% (38 680 cases)
> 20-29 years: 8% (3619 cases)
> 10-19 years: 1% (549 cases)
> <10 years: 1% (416 cases)

<a name="note-5" href="#ref-5">[5]</a>:

> Spectrum of disease (N = 44 415)
> Mild: 81% (36 160 cases)
> Severe: 14% (6168 cases)
> Critical: 5% (2087 cases)

Initial presentation — Pneumonia appears to be the most frequent serious manifestation of infection, characterized primarily by fever, cough, dyspnea, and bilateral infiltrates on chest imaging [35,52,56,57]. There are no specific clinical features that can yet reliably distinguish COVID-19 from other viral respiratory infections.

In a study describing 138 patients hospitalized with COVID-19 pneumonia in Wuhan, the most common clinical features at the onset of illness were [35]:

Other cohort studies of patients from Wuhan with confirmed COVID-19 have reported a similar range of clinical findings [35,56,90,91]. However, fever might not be a universal finding. In one study, fever was reported in almost all patients, but approximately 20 percent had a very low grade fever <100.4°F/38°C [56]. In another study of 1099 patients from Wuhan and other areas in China, fever (defined as an axillary temperature over 99.5°F/37.5°C) was present in only 44 percent on admission but was ultimately noted in 89 percent during the hospitalization [52].

Although not highlighted in the initial cohort studies from China, smell and taste disorders (eg, anosmia and dysgeusia) have also been reported as common symptoms in patients with COVID-19 [92-94]. In a survey of 59 patients with COVID-19 in Italy, 34 percent self-reported either a smell or taste aberration and 19 percent reported both [93]. Whether this is a distinguishing feature of COVID-19 is uncertain.

Other, less common symptoms have included headache, sore throat, and rhinorrhea.