Covid how long contagious

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COVID-19: Duration of Contagiousness

Incubation Period of COVID-19

The incubation period of COVID-19, which is the time between exposure to the virus and the onset of symptoms, has been a critical focus for understanding the spread of the disease. Studies have shown that the median incubation period is approximately 5 days, with most individuals developing symptoms within 11.5 days of infection Lauer2020Park2020Linton2020. This period can extend up to 14 days, which is why quarantine measures typically last for two weeks Chaurasia2020Linton2020.

Duration of Infectiousness

Mild to Moderate Cases

For individuals with mild to moderate COVID-19, the infectious period is generally shorter. Research indicates that these patients are unlikely to be contagious beyond 10 days after symptom onset . This aligns with findings from multiple studies that have shown the virus is rarely isolated from patients after this period .

Severe or Critical Cases

In contrast, patients with severe or critical illness, or those who are immunocompromised, may shed the virus for a longer duration. In some cases, the virus has been isolated up to 32 days after symptom onset . This extended period of infectiousness necessitates longer isolation and monitoring for these patients.

Asymptomatic and Pre-symptomatic Transmission

Asymptomatic Cases

The infectious period for asymptomatic individuals, who do not show symptoms but can still spread the virus, is estimated to be around 6.5 to 9.5 days . However, the infectivity of asymptomatic carriers may be weaker compared to symptomatic individuals. A study involving 455 contacts of an asymptomatic carrier found no secondary infections, suggesting that some asymptomatic carriers might have a lower transmission risk .

Pre-symptomatic Transmission

Pre-symptomatic transmission, where individuals spread the virus before showing symptoms, is also significant. The median pre-symptomatic infectious period ranges from less than 1 day to 4 days . This means that individuals can be contagious even before they realize they are infected, contributing to the rapid spread of the virus Nishiura2020Tindale2020.

Conclusion

Understanding the duration of contagiousness for COVID-19 is crucial for effective public health measures. While mild to moderate cases are generally not infectious beyond 10 days, severe cases and immunocompromised individuals may require longer isolation. Asymptomatic and pre-symptomatic transmissions pose additional challenges, emphasizing the importance of widespread testing and preventive measures to control the spread of COVID-19.

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Most relevant research papers on this topic

The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application

The median incubation period for COVID-19 is 5.1 days, similar to SARS, supporting current quarantine or active monitoring recommendations for potential exposed individuals.

Meta-AnalysisRigorous JournalHighly Cited

2020·

5449citations

·S. Lauer et al.

Annals of Internal Medicine·

DOI

Inferred duration of infectious period of SARS-CoV-2: rapid scoping review and analysis of available evidence for asymptomatic and symptomatic COVID-19 cases

Inferring the infectious period of COVID-19 from repeated diagnosis, viral loads, and replication data alone has limitations and potential patient recall bias, but data provides a preliminary evidence base for models.

Systematic ReviewRigorous JournalHighly Cited

2020·

372citations

·A. Byrne et al.

BMJ Open·

DOI

The duration of infectiousness of individuals infected with SARS-CoV-2

COVID-19 patients with mild-to-moderate illness are highly unlikely to be infectious beyond 10 days of symptoms, but those with severe-to-critical illness or immunocompromised may shed infectious virus for longer.

Systematic ReviewHighly Cited

2020·

157citations

·K. Walsh et al.

The Journal of Infection·

DOI

A Systematic Review of COVID-19 Epidemiology Based on Current Evidence

Current evidence suggests that COVID-19 epidemics take 3-7 days to double in size, with an incubation period of 4-6 days and a case fatality risk of 0.3% to 1.4% outside China.

Systematic ReviewRigorous JournalHighly Cited

2020·

542citations

·Minah Park et al.

Journal of Clinical Medicine·

DOI

The First 75 Days of Novel Coronavirus (SARS-CoV-2) Outbreak: Recent Advances, Prevention, and Treatment

SARS-CoV-2 has been highly contagious and highly transmissible, with combined antiviral treatment showing the highest success rate in treating infected patients.

Literature ReviewRigorous JournalHighly Cited

2020·

229citations

·Yuxin Yan et al.

International Journal of Environmental Research and Public Health·

DOI

COVID-19 and eye banking

COVID-19 is highly contagious and can be transmitted through respiratory droplets, contact with infected individuals, and ocular surface contact.

2020·

28citations

·S. Chaurasia et al.

Indian Journal of Ophthalmology·

DOI

Serial interval of novel coronavirus (COVID-19) infections

Abstract Objective To estimate the serial interval of novel coronavirus (COVID-19) from information on 28 infector-infectee pairs. Methods We collected dates of illness onset for primary cases (infectors) and secondary cases (infectees) from published research articles and case investigation reports. We subjectively ranked the credibility of the data and performed analyses on both the full dataset (n = 28) and a subset of pairs with highest certainty in reporting (n = 18). In addition, we adjust for right truncation of the data as the epidemic is still in its growth phase. Results Accounting for right truncation and analyzing all pairs, we estimated the median serial interval at 4.0 days (95% credible interval [CrI]: 3.1, 4.9). Limiting our data to only the most certain pairs, the median serial interval was estimated at 4.6 days (95% CrI: 3.5, 5.9). Conclusions The serial interval of COVID-19 is close to or shorter than its median incubation period. This suggests that a substantial proportion of secondary transmission may occur prior to illness onset. The COVID-19 serial interval is also shorter than the serial interval of severe acute respiratory syndrome (SARS), indicating that calculations made using the SARS serial interval may introduce bias.

Meta-AnalysisHighly Cited

2020·

1013citations

·H. Nishiura et al.

International Journal of Infectious Diseases·

DOI

Evidence for transmission of COVID-19 prior to symptom onset

Pre-symptomatic transmission of COVID-19 occurs in a large proportion of transmission events, emphasizing the importance of public health measures for controlling the pandemic.

Observational StudyRigorous JournalHighly Cited

2020·

270citations

·Lauren C. Tindale et al.

eLife·

DOI

Incubation Period and Other Epidemiological Characteristics of 2019 Novel Coronavirus Infections with Right Truncation: A Statistical Analysis of Publicly Available Case Data

The incubation period of COVID-19 is between 2-14 days, with a mean of 5 days, and a median time delay of 13 days from illness onset to death (17 days with right truncation).

Observational StudyRigorous JournalHighly Cited

2020·

1391citations

·Natalie M. Linton et al.

Journal of Clinical Medicine·

DOI

Unique epidemiological and clinical features of the emerging 2019 novel coronavirus pneumonia (COVID‐19) implicate special control measures

COVID-19 has unique epidemiological and clinical features, necessitating special control measures to address its spread and challenges.

Literature ReviewHighly Cited

2020·

1446citations

·Yixuan Wang et al.

Journal of Medical Virology·

DOI

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