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Transmission dynamics of monkeypox in the United Kingdom: contact tracing study

OBJECTIVE: To analyse the transmission dynamics of the monkeypox outbreak in the UK, declared a Public Health Emergency of International Concern in July 2022. DESIGN: Contact tracing study, linking data on case-contact pairs and on probable exposure dates. SETTING: Case questionnaires from the UK He...

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Autores principales: Ward, Thomas, Christie, Rachel, Paton, Robert S, Cumming, Fergus, Overton, Christopher E
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BMJ Publishing Group Ltd. 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9627597/
https://www.ncbi.nlm.nih.gov/pubmed/36323407
http://dx.doi.org/10.1136/bmj-2022-073153
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author Ward, Thomas
Christie, Rachel
Paton, Robert S
Cumming, Fergus
Overton, Christopher E
author_facet Ward, Thomas
Christie, Rachel
Paton, Robert S
Cumming, Fergus
Overton, Christopher E
author_sort Ward, Thomas
collection PubMed
description OBJECTIVE: To analyse the transmission dynamics of the monkeypox outbreak in the UK, declared a Public Health Emergency of International Concern in July 2022. DESIGN: Contact tracing study, linking data on case-contact pairs and on probable exposure dates. SETTING: Case questionnaires from the UK Health Security Agency (UKHSA), United Kingdom. PARTICIPANTS: 2746 people with polymerase chain reaction confirmed monkeypox virus in the UK between 6 May and 1 August 2022. MAIN OUTCOME MEASURES: The incubation period and serial interval of a monkeypox infection using two bayesian time delay models—one corrected for interval censoring (ICC—interval censoring corrected) and one corrected for interval censoring, right truncation, and epidemic phase bias (ICRTC—interval censoring right truncation corrected). Growth rates of cases by reporting date, when monkeypox virus was confirmed and reported to UKHSA, were estimated using generalised additive models. RESULTS: The mean age of participants was 37.8 years and 95% reported being gay, bisexual, and other men who have sex with men (1160 out of 1213 reporting). The mean incubation period was estimated to be 7.6 days (95% credible interval 6.5 to 9.9) using the ICC model and 7.8 days (6.6 to 9.2) using the ICRTC model. The estimated mean serial interval was 8.0 days (95% credible interval 6.5 to 9.8) using the ICC model and 9.5 days (7.4 to 12.3) using the ICRTC model. Although the mean serial interval was longer than the incubation period for both models, short serial intervals were more common than short incubation periods, with the 25th centile and the median of the serial interval shorter than the incubation period. For the ICC and ICRTC models, the corresponding estimates ranged from 1.8 days (95% credible interval 1.5 to 1.8) to 1.6 days (1.4 to 1.6) shorter at the 25th centile and 1.6 days (1.5 to 1.7) to 0.8 days (0.3 to 1.2) shorter at the median. 10 out of 13 linked patients had documented pre-symptomatic transmission. Doubling times of cases declined from 9.07 days (95% confidence interval 12.63 to 7.08) on the 6 May, when the first case of monkeypox was reported in the UK, to a halving time of 29 days (95% confidence interval 38.02 to 23.44) on 1 August. CONCLUSIONS: Analysis of the instantaneous growth rate of monkeypox incidence indicates that the epidemic peaked in the UK as of 9 July and then started to decline. Short serial intervals were more common than short incubation periods suggesting considerable pre-symptomatic transmission, which was validated through linked patient level records. For patients who could be linked through personally identifiable data, four days was the maximum time that transmission was detected before symptoms manifested. An isolation period of 16 to 23 days would be required to detect 95% of people with a potential infection. The 95th centile of the serial interval was between 23 and 41 days, suggesting long infectious periods.
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spelling pubmed-96275972022-11-03 Transmission dynamics of monkeypox in the United Kingdom: contact tracing study Ward, Thomas Christie, Rachel Paton, Robert S Cumming, Fergus Overton, Christopher E BMJ Research OBJECTIVE: To analyse the transmission dynamics of the monkeypox outbreak in the UK, declared a Public Health Emergency of International Concern in July 2022. DESIGN: Contact tracing study, linking data on case-contact pairs and on probable exposure dates. SETTING: Case questionnaires from the UK Health Security Agency (UKHSA), United Kingdom. PARTICIPANTS: 2746 people with polymerase chain reaction confirmed monkeypox virus in the UK between 6 May and 1 August 2022. MAIN OUTCOME MEASURES: The incubation period and serial interval of a monkeypox infection using two bayesian time delay models—one corrected for interval censoring (ICC—interval censoring corrected) and one corrected for interval censoring, right truncation, and epidemic phase bias (ICRTC—interval censoring right truncation corrected). Growth rates of cases by reporting date, when monkeypox virus was confirmed and reported to UKHSA, were estimated using generalised additive models. RESULTS: The mean age of participants was 37.8 years and 95% reported being gay, bisexual, and other men who have sex with men (1160 out of 1213 reporting). The mean incubation period was estimated to be 7.6 days (95% credible interval 6.5 to 9.9) using the ICC model and 7.8 days (6.6 to 9.2) using the ICRTC model. The estimated mean serial interval was 8.0 days (95% credible interval 6.5 to 9.8) using the ICC model and 9.5 days (7.4 to 12.3) using the ICRTC model. Although the mean serial interval was longer than the incubation period for both models, short serial intervals were more common than short incubation periods, with the 25th centile and the median of the serial interval shorter than the incubation period. For the ICC and ICRTC models, the corresponding estimates ranged from 1.8 days (95% credible interval 1.5 to 1.8) to 1.6 days (1.4 to 1.6) shorter at the 25th centile and 1.6 days (1.5 to 1.7) to 0.8 days (0.3 to 1.2) shorter at the median. 10 out of 13 linked patients had documented pre-symptomatic transmission. Doubling times of cases declined from 9.07 days (95% confidence interval 12.63 to 7.08) on the 6 May, when the first case of monkeypox was reported in the UK, to a halving time of 29 days (95% confidence interval 38.02 to 23.44) on 1 August. CONCLUSIONS: Analysis of the instantaneous growth rate of monkeypox incidence indicates that the epidemic peaked in the UK as of 9 July and then started to decline. Short serial intervals were more common than short incubation periods suggesting considerable pre-symptomatic transmission, which was validated through linked patient level records. For patients who could be linked through personally identifiable data, four days was the maximum time that transmission was detected before symptoms manifested. An isolation period of 16 to 23 days would be required to detect 95% of people with a potential infection. The 95th centile of the serial interval was between 23 and 41 days, suggesting long infectious periods. BMJ Publishing Group Ltd. 2022-11-02 /pmc/articles/PMC9627597/ /pubmed/36323407 http://dx.doi.org/10.1136/bmj-2022-073153 Text en © Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ. https://creativecommons.org/licenses/by-nc/4.0/This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/ (https://creativecommons.org/licenses/by-nc/4.0/) .
spellingShingle Research
Ward, Thomas
Christie, Rachel
Paton, Robert S
Cumming, Fergus
Overton, Christopher E
Transmission dynamics of monkeypox in the United Kingdom: contact tracing study
title Transmission dynamics of monkeypox in the United Kingdom: contact tracing study
title_full Transmission dynamics of monkeypox in the United Kingdom: contact tracing study
title_fullStr Transmission dynamics of monkeypox in the United Kingdom: contact tracing study
title_full_unstemmed Transmission dynamics of monkeypox in the United Kingdom: contact tracing study
title_short Transmission dynamics of monkeypox in the United Kingdom: contact tracing study
title_sort transmission dynamics of monkeypox in the united kingdom: contact tracing study
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9627597/
https://www.ncbi.nlm.nih.gov/pubmed/36323407
http://dx.doi.org/10.1136/bmj-2022-073153
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