Incubation period and serial interval of Covid-19 in a chain of infections in Bahia Blanca (Argentina)
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Abstract
Objective
To estimate the incubation period and the serial interval of Covid-19 from a sample of symptomatic patients in Bahia Blanca city.
Methods
We collected dates of illness onset for primary cases (infectors) and secondary cases (infectees) for the first 18 secondary patients infected with SARS-Cov-2 in Bahia Blanca (Argentina). We ranked the fiability of the data depending upon certainty about the identification of the infector and the date of exposition to infector.
The sample has some missing values. In the case of incubation, as 3 patients were infected by other household members, we only have 15 observations with an observed date of exposition. For the estimation of serial interval, one patient became ill from close contact with an asymptomatic infectious. Also, estimations of both the incubation period and the serial interval were carried using the full sample and a subsample with higher certainty about the transmissor and date of exposition. By the time the dataset was prepared all infectors were recovered so estimations do need to take into account right censoring.
Results
The mean incubation period for symptomatic patients is 7.9 days (95% CI: 4.6, 11.1) considering the sample of 15 cases patients and 7.5 days (95% CI: 4.1, 10.9) if the sample is restricted to the most certain cases (n=12). The median is 6.1 (95% CI: 4.1, 9.2) and 5.8 (95% CI: 3.6, 9.3) respectively. Moreover, 97.5% of symptomatic cases will develop symptoms afert 13.6 days from exposition (95% CI 10.7, 16.5).
The point estimation for the mean serial interval is 6.8 days (95% CI: 4.0-9.6). Considering only the most certain pairs, the mean serial interval is estimated at 5.5 days (95% CI: 2.8, 8.1). The estimated median serial intervals were 5.2 (95% CI: 3.0, 8.1) and 4.1 (95% CI: 2.0, 6.9) days respectively.
Conclusions
Evidence from Bahia Blanca (Argentina) suggests that the median and mean serial interval of Covid-19 is shorter than the incubation period. This suggests that a pre-symptomatic transmission is not negligible. Comparisons with foreign estimates show that incubation period and serial interval could be longer in Bahia Blanca city than in other regions. That poses a signal of opportunity to attain more timely contact tracing and effective isolation.
Highlights
We estimate the incubation period in a sample of 15 symptomatic patients with Covid-19 in Bahia Blanca city (Argentina).
We estimate the serial interval for Covid-19 infections in a sample of 17 infector-infectee pairs detected in Bahia Blanca city (Argentina).
The median serial interval is lower to the median incubation period, suggesting a transmission is taking place also during the pre-symptomatic phase.
The incubation period and serial interval of Covid-19 in Bahía Blanca city seem to take more days than in Asian regions. This finding slows down the pace of health assistance to patients (conditional to public interventions).
Longer serial intervals help in tracing contacts and show relative slow turnover of case generations. At the same time, if symptoms take longer time to emerge, long serial intervals may also increase the reproductive number if contact tracing and effective isolation measures are placed untimely.
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SciScore for 10.1101/2020.06.18.20134825: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:The present study has some limitations. First, from the first 36 cases 33% of symptomatic cases are hospital staff for whom contagion is clearly during symptomatic phase and not before. If transmission becomes communitary, …
SciScore for 10.1101/2020.06.18.20134825: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:The present study has some limitations. First, from the first 36 cases 33% of symptomatic cases are hospital staff for whom contagion is clearly during symptomatic phase and not before. If transmission becomes communitary, pre-symptomatic contagion could be higher than estimated one.
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
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