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. 2021 May 19;21(1):453.
doi: 10.1186/s12879-021-06107-6.

Identification of transmission chains and clusters associated with COVID-19 in Tunisia

Mouna Safer  1   2 , Hejer Letaief  3   4 , Aicha Hechaichi  3   4 , Chahida Harizi  5 , Sonia Dhaouadi  3 , Leila Bouabid  3 , Sondes Darouiche  3 , Donia Gharbi  3 , Nawel Elmili  3 , Hamida Ben Salah  3 , Mongi Hammami  3 , Khouloud Talmoudi  3 , Rim Moussa  6 , Nejib Charaa  6 , Hasna Termiz  6 , Fethi Ltaief  6 , Habib Tounekti  6 , Mohamed Makhlouf  6 , Asma Belguith Sriha  7 , Manel Ben Fredj  7 , Sonia Khalfallah  6 , Houcine Jabrane  6 , Selma Mchirgui  6 , Chedli Amich  6 , Radhia Dabghi  6 , Zid Anez  6 , Latifa Abdelkader  6 , Moncef Mhamdi  6 , Nabil Ouerfeli  6 , Salah Zoghlami  6 , Souha Bougatef  3   4 , Mohamed Kouni Chahed  8 , Nissaf Bouafif Ben Alaya  3   4
Affiliations

Identification of transmission chains and clusters associated with COVID-19 in Tunisia

Mouna Safer et al. BMC Infect Dis. .

Abstract

Background: The aim of this study was to characterize the transmission chains and clusters of COVID-19 infection in Tunisia.

Methods: All cases were confirmed by Reverse Transcriptase Polymerase Chain Reaction of a nasopharyngeal specimen. Contact tracing is undertaken for all confirmed cases in order to identify close contacts that will be systematically screened and quarantined. Transmission chains were identified based on field investigation, contact tracing, results of screening tests and by assessing all probable mode of transmission and interactions.

Results: As of May 18, 2020, 656 cases out of a total of 1043 confirmed cases of Coronavirus disease 2019 belong to 127 transmission chains identified during the epidemic (mean age 42.36 years, Standard deviation 19.56 and sex ratio 0.86). The virus transmission is the most concentrated in the governorate of Tunis (31.5%), Ariana (10.2%) and Ben Arous (10.2%). Virus transmission occurred 50 times (9.72% of secondary transmission events) between two different governorates. A maximum of seven generations of secondary infection was identified, whereas 62% of these secondary infections belong the first generation. A total of 11 "super spreader" cases were identified in this investigation. Four large clusters have been identified. The evolution of secondary cases highlighted two peaks: one in 2nd April and a second in 16 th April whereas imported cases caused local transmission of virus during the early phase of the epidemic.

Conclusion: Correct contact tracing and early active case finding is useful to identify transmission chains and source of infection in order to contain the widespread transmission in the community.

Keywords: COVID-19; Cluster analysis; Contact tracing; Coronavirus infections / transmission; Public health; Tunisia.

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Conflict of interest statement

Authors declare no conflict of interest.

Figures

Fig. 1
Fig. 1
Cases were differentiated by respective generations of secondary infection (as of May 18 2020), origin of transmission (local/imported) and governorates. A total of 643 cases were presented after excluding 13 unclassified ones. Different generations were presented with circles of different size and a different shade of blue color (from the first to the seventh generation of secondary transmission the circles are smaller and less dark)
Fig. 2
Fig. 2
Generation of secondary infection of COVID-19 by governorate, Tunisia March–May 2020
Fig. 3
Fig. 3
Confirmed cases of secondary infection among documented transmission chains of COVID 19, Tunisia March–May 2020
Fig. 4
Fig. 4
Confirmed index cases among documented transmission chains of COVID 19, Tunisia March–May 2020
See this image and copyright information in PMC

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