How long is covid contagious for
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Duration of COVID-19 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, is a critical factor in understanding its contagiousness. Studies have shown that the median incubation period is approximately 5.1 days, with 97.5% of symptomatic cases developing symptoms within 11.5 days of infection1. This period can extend up to 14 days, which is why quarantine measures often last for two weeks5 7.
Infectious Period in Symptomatic and Asymptomatic Cases
The duration of the infectious period varies between symptomatic and asymptomatic individuals. For symptomatic cases, the mean time from symptom onset to two negative RT-PCR tests is around 13.4 days, although this can be shorter in children or less severe cases2. The potential maximal infectious period, from symptom onset to hospital discharge or death, averages 18.1 days2.
For asymptomatic cases, the median infectious period is estimated to be between 6.5 to 9.5 days2. However, the infectivity of asymptomatic carriers is generally considered to be weaker compared to symptomatic individuals6.
Pre-symptomatic Transmission
Pre-symptomatic transmission, where individuals spread the virus before showing symptoms, is also a significant factor. The median pre-symptomatic infectious period ranges from less than one day to four days2. This suggests that a substantial portion of secondary transmission may occur before the onset of symptoms9.
Summary of Contagious Period
In summary, COVID-19 can be contagious for a period that spans from a few days before symptom onset to several days after. Symptomatic individuals are typically infectious for about 13 to 18 days, while asymptomatic carriers may be contagious for around 6.5 to 9.5 days2 6. The variability in these periods underscores the importance of continued vigilance and adherence to public health guidelines to mitigate the spread of the virus.
Conclusion
Understanding the duration of COVID-19's contagiousness is crucial for effective public health interventions. The infectious period can vary significantly between individuals, with symptomatic cases generally being contagious for a longer duration than asymptomatic ones. Pre-symptomatic transmission further complicates containment efforts, highlighting the need for comprehensive strategies to control the spread of the virus.
Sources and full results
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-Analysis
Rigorous Journal
Highly CitedInferred 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 CitedThe 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 CitedA 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 CitedCOVID-19 and eye banking
COVID-19 is highly contagious and can be transmitted through respiratory droplets, contact with infected individuals, and ocular surface contact.
A study on infectivity of asymptomatic SARS-CoV-2 carriers
Asymptomatic SARS-CoV-2 carriers' infectivity may be weak, as all 455 contacts were excluded from infection.
Rigorous JournalHighly CitedCOVID-19 and SARS-CoV-2 Variants: Current Challenges and Health Concern
COVID-19 is a contagious and pathogenic virus with limited antiviral agents and vaccines, posing a global health challenge and requiring consistent monitoring and surveillance.
COVID-19: clinical and laboratory manifestations in novel coronavirus infection
COVID-19 is a highly contagious disease caused by the coronavirus SARS-CoV-2, with high mortality in a small portion of infected individuals, and nonspecific laboratory biomarkers can predict complications and help identify asymptomatic carriers or mild symptoms.
Highly CitedSerial 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.
Highly CitedUnique 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