Estimation of Incubation Period of Mpox during 2022 Outbreak in Pereira, Colombia

We estimated the incubation period for mpox during an outbreak in Pereira, Colombia, using data from 11 confirmed cases. Mean incubation period was 7.1 (95% CI 4.9–9.9) days, consistent with previous outbreaks. Accurately estimating the incubation period provides insights into transmission dynamics, informing public health interventions and surveillance strategies.


The Study
We conducted a descriptive cross-sectional epidemiologic study using data extracted from field epidemiologic investigation of 11 reverse transcription PCRconfirmed cases of mpox in Pereira, Colombia, from the national reference laboratory of the National Institute of Health of Colombia.Case investigations were performed by a coinvestigator with training and experience in conducting epidemiologic interviews.Investigators gathered information from patients on travel history within the 21 days before symptom onset and any potential exposure events from a list of events developed from scientific publications on the 2022 mpox outbreak (4,6).Events included having multiple sexual encounters or new sexual partners, attending LGBTQ+ venues such as saunas and venues for sexual encounters involving chemsex (sexual activity while under the influence of drugs), or social gatherings involving intimate contact, including sexual activity.
We used 2 approaches to collect data on date of exposure.If during the initial interview a case-patient reported an exact date potentially related to exposure to mpox infection, we recorded that as probable date of exposure.If the case-patient identified multiple potential exposure times, we recorded the longest period of time during which visits to places or situations for potential monkeypox virus transmission.That second

Estimation of Incubation Period of Mpox during 2022 Outbreak in Pereira, Colombia
We estimated the incubation period for mpox during an outbreak in Pereira, Colombia, using data from 11 confirmed cases.Mean incubation period was 7.1 (95% CI 4.9-9.9)days, consistent with previous outbreaks.Accurately estimating the incubation period provides insights into transmission dynamics, informing public health interventions and surveillance strategies.
approach generated censored interval data in which occurrence of the transmission event was known, but not the exact timing.
For the date of onset, we used the day in the prodromal period on which symptoms were first reported, including nonspecific symptoms such as fever, fatigue, headache, lymphadenopathy, muscle pain, sore throat, or rash.We resolved inconsistencies in dates and missing data through follow-up telephone interviews.We conducted an event-time analysis to estimate the distribution that would best fit the incubation periods of the cases.Because measurements corresponded to both interval-censored and left-censored data, as explained elsewhere (9), we constructed a dataset with these characteristics.We used 3 parametric distributions-gamma, Weibull, and log-normal-to determine the best fit for the analytic model.We evaluated the fitted models using the corrected Akaike information criterion (AICc) to obtain the lowest value, which indicates a better model fit.We performed all analyses in R software icenReg package version 2015 (https://cran.r-project.org/web/packages/icenReg/index.html) using the maximum-likelihood method (10).
All 11 mpox case-patients included in our analysis were men who reported having sexual contact with other men.Median age was 34 (range 22-53, interquartile range 27-41) years.Symptoms commonly reported were myalgia, headache, fever, and lymphadenopathy.Only 1 case-patient did not manifest genital lesions, and only 2 did not have a previous HIV diagnosis.Dates of probable exposure for the 11 patients were July 9-September 10, 2022; dates of first symptom onset were July 11-September 20, 2022.Exposure window was 1 day in 6/11 cases; maximum exposure window was 8 days (1 case) and minimum 1 day.
Mpox might exhibit a shorter incubation period in invasive or complex exposures, in which the patient experienced contact through damaged skin or mucous membranes; typical incubation period is 9 days in those exposures (4).Mean mpox incubation period in MSM during this outbreak was 7.1 days,

Conclusions
Establishing precise and accurate estimates of the temporal distribution of incubation periods for emerging infectious diseases is crucial for case definition and to inform public health policies.Robust inference methods that account for interval censoring in the estimations are recommended.Regarding potential transmission associated with sexual contact during the mpox outbreak ( 6), the complex and varied nature of those types of exposure should be carefully considered and incorporated into epidemiologic findings.We obtained the data on which this study was based from initial epidemiologic investigations of cases during a mpox outbreak in the city of Pereira, Colombia.The small sample size (11 case-patients) was a limitation of this study.
Our study provides empirical evidence of the incubation period in the 2022 mpox outbreak, illustrated by the Weibull distribution graph, using data on exposure history and symptom onset in cases confirmed using PCR testing in Colombia and Latin America.The upper limit of the confidence interval for the estimated 95th percentile, 22.6 days, supports the recommendation of using a 21-day monitoring period for potential mpox cases involving close contact to limit further spread of the infection.Understanding the incubation period and its variability contributes to the development of targeted control strategies and enhances our knowledge of this emerging infectious disease.

Figure .
Figure.Comparison of parametric distributions from different models for the incubation period of mpox for patients in Pereira, Colombia.

Table .
Estimated mean and percentile parametric distributions for incubation period in 11 confirmed cases of mpox, Pereira, Colombia* *P5, P50, and P95 indicate the percentiles of the estimated distribution.AICc, corrected Akaike information criterion