SARS-CoV-2 infection control implementation based on sources of infection showing directions for three age groups in Japan

  1. Atsuko Hata
  2. Junko Kurita
  3. Eri Muso
  4. Toshiro Katayama
  5. Takahide Hata
  6. Yasushi Ohkusa

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Abstract

Background

Some aspects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission in children and adults remain unclear. This report describes different SARS-CoV-2 transmission patterns by age group in Japan.

Methods and findings

This retrospective observational case series study analyzed transmission patterns of real-time polymerase chain reaction (RT-PCR)-confirmed SARS-CoV-2 infections found by local health authorities and commercial laboratories during January 14 through July 31, 2020 in Japan. After ascertaining the infection source for every symptomatic case as clusters at households, daycare facilities, schools, hospitals and workplaces etc., their associated transmission patterns were analyzed. Identified cases were divided into three groups: underage, < 20; adults, 20–59; and elderly people 60 years old and older. The reproductive number (R)s of respective transmission directions found for the respective age groups were compared.

Of 26,986 total cases, 23,746 unknown cases were found, leaving 3,240 ascertained sources of infection (12.0%) comprising 125 (3.9%) underage, 2350 (72.5%) adult, and 765 (23.6%) elderly people. The respective Rs of underage infection sources directed to underage, adult, and elderly people were estimated respectively as 0.0415 (95% CI, 0.0138–0.0691), 1.11 (95% CI, 0.9171–1.3226), and 0.2811 (95% CI, 0.2074–0.3687). The respective Rs of adult infection source directed to underage, adult, and elderly people were estimated respectively as 0.0140 (95% CI, 0.0120–0.0162), 0.5392 (95% CI, 0.5236–0.5550), and 0.1135 (95% CI, 0.1074–0.1197). The respective Rs of elderly infection source directed to underage, adult, and elderly people were estimated as 0.065 (95% CI, 0.0039–0.0091), 0.3264 (95% CI, 0.3059–0.3474), and 0.3991 (95% CI, 0.3757–0.4229).

Conclusions

The main sources of SARS-CoV-2 infection were adults and elderly people. The R of underage people directed to adults was greater than 1 because of close familial contact but they were unlikely to become carriers transmitting SARS-CoV-2 because they accounted for a minority for transmissions. Apparently, SARS-CoV-2 was transmitted among adults and elderly people, suggesting that infection control of SARS-CoV-2 should be managed specifically by generation.

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  1. ScreenIT

    SciScore for 10.1101/2021.01.14.21249637: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot 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:
    This study presents several important limitations. The most important limitation of this paper is that it analyzes only symptomatic individuals. This is true because, to study asymptomatic persons around the infected person, it is necessary to examine all the contact persons of the infected person, so that only a part of the relation is invariably acquired. As a result, the proportion of infected individuals is significantly lower than that of symptomatic individuals. A simple sum of the two does not make sense. However, it has been suggested that SARS Co-V2 is highly infectious even among asymptomatic individuals. It cannot be ruled out that the asymptomatic epidemic might spread in schools or nurseries if the proportion of asymptomatic children is high and their infectivity is high. To confirm this point, continuous inspection of all children and children at school or nursery school is necessary. No such design findings in the future have been published at this time. Apparently, future consideration is necessary. Second, the data we used were based solely on information obtained through interviews by health center staff. Necessarily, not all information was disclosed. Analyses were conducted as well as possible given the limited data which were obtained. However, there were 506 unknown cases other than the 341 determined cases as sources of infection. Moreover, we did not measure viral loads in COVID-19 patients in these transmission clusters. Further studies should be cond...

    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.

    About SciScore

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  2. Version published to 10.1101/2021.01.14.21249637v1 on medRxiv