Contact Tracing Assessment of COVID-19 Transmission Dynamics in Taiwan and Risk at Different Exposure Periods Before and After Symptom Onset | Global Health | JAMA Internal Medicine | JAMA Network
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    2 Comments for this article
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    Secondary Attack Rate for COVID-19 infections in Taiwan
    Robert Albrecht, MD |
    In this population of 100 COVID-19 patients there were  only 22 other infections. A R0 for the virus of about 2.5 would suggest 100 infections would lead to approximately  250 infections. What is the explanation?
    CONFLICT OF INTEREST: None Reported
    COVID-19 Transmission Dynamics in Taiwan
    Susanne Wagner, Ph.D. | Commercial diagnostics provider
    Data are inconsistent between Table 2 and Table 3.
    Total contacts in the non-household family category are listed as 76 in Table 2, but only 68 are present in Table 3.
    Total contacts in the Others category are listed as 1836 in Table 2, but add up to only 1754 in Table 3.
    Any explanation?


    The Comment was referred to the authors of the article who provided the following response:

    font-size: 12pt; font-family: calibri, sans-serif;"> 

    “The inconsistency of numbers in Table 2 and Table 3 is due to the missing data of exposure time in some types of contacts. The numbers of missing data in different types of contacts was discussed in the Methods and shown in Table 1. 

     

    For example, in the group of non-household family contacts, the total number was 76, and the number of missing data for exposure time was 8. Therefore the number of family contacts put in the analysis in Table 3 was only 68.”

     

    CONFLICT OF INTEREST: None Reported
    READ MORE
    Original Investigation
    May 1, 2020

    Contact Tracing Assessment of COVID-19 Transmission Dynamics in Taiwan and Risk at Different Exposure Periods Before and After Symptom Onset

    Author Affiliations
    • 1Epidemic Intelligence Center, Taiwan Centers for Disease Control, Taipei, Taiwan
    • 2Institute of Epidemiology and Preventive Medicine, National Taiwan University College of Public Health, Taipei, Taiwan
    • 3Office of Preventive Medicine, Taiwan Centers for Disease Control, Taipei, Taiwan
    • 4Global Health Program, National Taiwan University College of Public Health, Taipei, Taiwan
    JAMA Intern Med. 2020;180(9):1156-1163. doi:10.1001/jamainternmed.2020.2020
    Key Points

    Question  What is the transmissibility of coronavirus disease 2019 (COVID-19) to close contacts?

    Findings  In this case-ascertained study of 100 cases of confirmed COVID-19 and 2761 close contacts, the overall secondary clinical attack rate was 0.7%. The attack rate was higher among contacts whose exposure to the index case started within 5 days of symptom onset than those who were exposed later.

    Meaning  High transmissibility of COVID-19 before and immediately after symptom onset suggests that finding and isolating symptomatic patients alone may not suffice to interrupt transmission, and that more generalized measures might be required, such as social distancing.

    Abstract

    Importance  The dynamics of coronavirus disease 2019 (COVID-19) transmissibility are yet to be fully understood. Better understanding of the transmission dynamics is important for the development and evaluation of effective control policies.

    Objective  To delineate the transmission dynamics of COVID-19 and evaluate the transmission risk at different exposure window periods before and after symptom onset.

    Design, Setting, and Participants  This prospective case-ascertained study in Taiwan included laboratory-confirmed cases of COVID-19 and their contacts. The study period was from January 15 to March 18, 2020. All close contacts were quarantined at home for 14 days after their last exposure to the index case. During the quarantine period, any relevant symptoms (fever, cough, or other respiratory symptoms) of contacts triggered a COVID-19 test. The final follow-up date was April 2, 2020.

    Main Outcomes and Measures  Secondary clinical attack rate (considering symptomatic cases only) for different exposure time windows of the index cases and for different exposure settings (such as household, family, and health care).

    Results  We enrolled 100 confirmed patients, with a median age of 44 years (range, 11-88 years), including 44 men and 56 women. Among their 2761 close contacts, there were 22 paired index-secondary cases. The overall secondary clinical attack rate was 0.7% (95% CI, 0.4%-1.0%). The attack rate was higher among the 1818 contacts whose exposure to index cases started within 5 days of symptom onset (1.0% [95% CI, 0.6%-1.6%]) compared with those who were exposed later (0 cases from 852 contacts; 95% CI, 0%-0.4%). The 299 contacts with exclusive presymptomatic exposures were also at risk (attack rate, 0.7% [95% CI, 0.2%-2.4%]). The attack rate was higher among household (4.6% [95% CI, 2.3%-9.3%]) and nonhousehold (5.3% [95% CI, 2.1%-12.8%]) family contacts than that in health care or other settings. The attack rates were higher among those aged 40 to 59 years (1.1% [95% CI, 0.6%-2.1%]) and those aged 60 years and older (0.9% [95% CI, 0.3%-2.6%]).

    Conclusions and Relevance  In this study, high transmissibility of COVID-19 before and immediately after symptom onset suggests that finding and isolating symptomatic patients alone may not suffice to contain the epidemic, and more generalized measures may be required, such as social distancing.

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