Skip to content

Clinical course of COVID-19 patients: share of asymptomatic patients, mild shapes, severe, incubation time, duration of the contagious phase.

Clinical course of COVID-19 patients: share of asymptomatic patients, mild shapes, severe, incubation time, duration of the contagious phase.

SARS-COV-2 is a virus that we've been getting to know these months, extremely contagious that can occur with very different forms from subject to subject, going from completely asymptomatic forms to fatal forms in a few days.
The duration of the incubation period, the contagious phase and symptomatic phase are extremely variable.
I did a Literature review to try to do some’ and summarized the MEDI data in the attached chart.
This graph is useful for having an epidemiological’epidemiological idea of the behavior of the virus but of course it should not be interpreted as a means of predicting the #8217;performance of the individual patient.
We often see patients with extremely prolonged hospitalizations and positive swab even after 3 weeks from the resolution of the symptoms.


I tried to enter the data as correctly as possible, some parts of the graph have been hypothesized critically, I'll report the sources used and the reasoning made.

The data I started from:
-Patients Asymptomatic: 30.8% (IC95: 7.7–53.8%) [1].

Incubation: Average 5.0 days (IC95 4.4 to 5.6 Days), Range 2-14 days [2]

gravity breakdown symptomatic cases: mild cases 81%, severe cases 14%, critical cases 5% (percentages of the total number of symptomatic: 69.2%) [3]

beginning of the contagious phase: 2.55 – 2.89 before the onset of symptoms [4] From item to preprint

duration of the contagious phase estimated by viremia found in mild and severe cases [5]

duration of hospitalization: Average 12 Days (IQR function , 9-13 days) [6] I used this data to estimate the average duration of symptoms in mild and severe forms, Arbitrarily.

-“The mean onset of symptoms prior to presenting to the hospital was 3.5 Days, and 17 patients (81%) were admitted to the ICU less than 24 hours after hospital admission” [7]

– “Among patients still in the ICU (n = 920), the median (IQR function) length of stay was 10 Days (8-14 [95% CI, 10-11])” [8]

-There is evidence of contagiousness subjects but not the duration of the contagious phase in asymptomatics. It seemed reasonable to assume a shorter period than subjects with mild forms.

I hope that the graph and this analysis can help to clarify and understand what role asymptomatic and paucystomatic subjects are playing in this epidemic.
And’ also important to understand that subjects can remain contagious for a long time after remission of symptoms and that therefore it is good to be cautious and recommend a convalescence in isolation long enough.

I am as always open to dialogue, I appreciate reports of errors/inaccuracies.

For those who want to share the chart from my page:

[1] Nishiura H, Kobayashi T, Suzuki A, et al. Estimation of the asymptomatic ratio of novel coronavirus infections (COVID-19). Int J Infect Dis. March, New10 2020. Doi:10.1016/j.ijid.2020.03.020
[2] Linton NM, Kobayashi T, Yang Y, et al. Incubation Period and Other Epidemiological Characteristics of 2019 Novel Coronavirus Infections with Right Truncation: A Statistical Analysis of Publicly Available Case Data. J Clin Med. 2020;9(2). Doi:10.3390/jcm9020538
[3] Wu Z, McGoogan JM. Characteristics of and Important Lessons From the Coronavirus Disease 2019 (COVID-19) Outbreak in China: Summary of a Report of 72 314 Cases From the Chinese Center for Disease Control and Prevention. JAMA. February 2020. Doi:10.1001/jama.2020.2648
[4] Tindale L, Coombe M, Stockdale JE, et al. Transmission interval estimates suggest pre-symptomatic spread of COVID-19. medRxiv. January 2020:2020.03.03.20029983. Doi:10.1101/2020.03.03.20029983
[5] Liu Y, Yan L-M, Wan L, et al. Viral dynamics in mild and severe cases of COVID-19. Lancet Infect Dis. March, New10 2020. Doi:10.1016/S1473-3099(20)30232-2
[6] Iei liu, Jian-ya G. Clinical characteristics of 51 patients discharged from hospital with COVID-19 in Chongqing,China. medRxiv. January 2020:2020.02.20.20025536. Doi:10.1101/2020.02.20.20025536
[7] Arentz M, Yim E, Klaff L, et al. Characteristics and Outcomes of 21 Critically Ill Patients With COVID-19 in Washington State. JAMA. March, New10 2020. Doi:10.1001/jama.2020.4326
[8] Grasselli G, Zangrillo A, Zanella A, et al. Baseline Characteristics and Outcomes of 1591 Patients Infected With SARS-CoV-2 Admitted to ICUs of the Lombardy Region, Italy. JAMA. April 2020. Doi:10.1001/jama.2020.5394