COVID19 pneumonia

COVID19 Fact Sheet #2: Clinical features

COVID19 Fact Sheet #2: Clinical features


These fact sheets will provide data about characteristics, diagnosis, management, and prevention of COVID19. Fact sheet #2 will present known facts about clinical characteristics of the coronavirus disease (COVID19).


COVID19 incubation period

The incubation period for COVID19 is thought to be 4 to 5 days in most cases (maximum 14 days after exposure). In China symptoms would develop in 2.5 % of infected individuals within 2.2 days and in almost all infected individuals within 11.5 days


COVID19 illness severity

COVID19 symptoms range from mild to critical; most infections are not severe. The following degrees of illness exist:

  • Mild (no or mild pneumonia) 81 %.
  • Severe disease (e.g., with shortness of breath, low blood oxygen, or >50 % lung involvement on imaging within 24 to 48 hours) 14 %.
  • Critical disease (e.g., with respiratory failure, shock, or multiorgan failure) 5 %.
  • Deaths overall 2.3 %; no deaths were reported among noncritical cases.


According to a joint World Health Organization (WHO)-China fact-finding mission, fatality rate ranged from 5.8 % in Wuhan to 0.7 % in the rest of China. Most of the tragic outcomes have occurred in patients with advanced age or underlying medical conditions (including heart disease, diabetes, chronic lung disease, high blood pressure, and cancer).


The proportion of severe or fatal infections may vary by location: in Italy, 12 % of all proven COVID19 cases and 16 % of all hospital patients with COVID19 needing intensive care. Here the estimated rate of deadly outcomes was 5.8 %. In contrast, the estimated case fatality rate in South Korea was 0.9 %. This may be related to age: in Italy, the median age of patients with infection was 64 years, whereas in Korea the median age was in the 40s.


COVID19 impact of age

Individuals of any age can acquire COVID19, although adults of 49 to 56 years and older are most commonly affected.

Older age is associated with increased deadliness of the infection (8% among those aged 70 to 79 years, and 15% among 80 years or older).


Symptomatic infection in children appears to be uncommon; when it occurs, it is usually mild, and only few severe cases have been reported. In China, only 2 % of infections were in individuals younger than 20 years old, and in South Korea, only 6.3 % of infections occurred in those younger than 20 years of age. In China, children’s illness was mild; fever, which resolved within 24 hours, cough, and sore throat. Few showed pneumonia on CT, seldom was intensive care needed; all children recovered.


COVID19 infections without symptoms

Asymptomatic infections have been described, but, for obvious reasons, their frequency is unknown. (In a COVID19 outbreak on a cruise ship where nearly all passengers and staff were tested for COVID19, approximately 17 % of the people on board tested positive, and about half of the 619 confirmed COVID19 cases were asymptomatic at the time of diagnosis.)


Even patients without symptoms may have objective clinical findings, e.g. CT imaging abnormalities. Low-grade fever, with or without other typical symptoms may occur a few days after diagnosis.


COVID19 clinical manifestations

Beginning stage

There are no symptoms that can reliably distinguish COVID19 from other virus infections of the respiratory system.


Pneumonia appears to be the most frequent serious manifestation of COVID19:

  • Fever,
  • Cough,
  • Shortness of breath,
  • And findings on chest imaging.


Most common symptoms in the beginning of illness were:

  • Fever in 99 % (Fever may be low: <100.4°F/38°C)
  • Fatigue in 70 %
  • Dry cough in 59 %
  • Lack of appetite in 40 %
  • Muscle pain in 35 %
  • Shortness of breath in 31 %
  • Cough with phlegm production in 27 %
  • Up to one half of patients may have digestive symptoms (e.g., nausea and diarrhea), in addition to respiratory symptoms.


Other symptoms:

  • Headache,
  • Sore throat,
  • Runny nose.


Course and complications

  • As above, severity of illness can range from mild to critical.
  • Sometimes, after initially mild symptoms, illness may progress over the course of a week.
  • Lung failure (Acute respiratory distress syndrome ARDS) is a major complication in patients with severe disease, particularly in those patients more than 65 years of age, with diabetes and hypertension
  • Other complications have included heart rhythm abnormalities, acute heart disease, and shock.
  • According to the WHO, recovery seems to require around two weeks for mild infections and three to six weeks for severe disease.


COVID19 Laboratory findings

  • The white blood cell count can vary: too few or too many white blood cells may occur.
  • Enzymes like lactate dehydrogenase or aminotransferase may be increased
  • Ferritin, an iron transporter can increase as well, as a part of the defensive immune response.


COVID19 Imaging findings

Chest CT in patients with COVID19 most commonly shows abnormalities, consistent with virus pneumonia. Nonetheless, while being helpful in making the diagnosis, chest CT can neither completely rule in or rule out COVID19.




Lodish H, Berk A, Zipursky SL, et al.:  Molecular Cell Biology. 4th edition. New York: W. H. Freeman; 2000.(

Marco Cascella; Michael Rajnik; Arturo Cuomo; Scott C. Dulebohn; Raffaela Di Napoli: Features, Evaluation and Treatment Coronavirus (COVID-19). ( )


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