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Infection rate among close contacts of patients with coronavirus disease in Japan: a descriptive study and literature review


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Factors that determine the presence or absence of SARS-CoV-2 infection by close contact.

Odds ratio 95% confidence interval Lower-Upper P
Age 1.00 0.997–1.010 0.227
Underlying disease 1.19 0.853–1.660 0.306
Female 2.23 1.700–2.930 <0.0001

Characteristics of the cases of SARS-CoV-2 infection in Fukui Prefecture, Japan.

Period 1* (n = 122) Period 2 (n = 122) Period 3 (n = 301) P
Age (years;IQR) 54 (45.3–66) 59 (42–77) 48 (28–66) <0.0001§
  0–10 2 (1.6) 1 (0.8) 12 (4) 0.178
  11–20 3 (2.5) 6 (4.9) 24 (8) 0.081
  21–30 7 (5.7) 12 (4.9) 55 (18.3) 0.001||
  31–40 14 (11.5) 10 (8.2) 38 (12.6) 0.444
  41–50 18 (14.8) 12 (9.8) 39 (13.0) 0.536
  51–60 36 (29.5) 10 (8.2) 43 (14.3) <0.0001**
  >61 42 (34.4) 71 (58.2) 90 (29.9) <0.0001††
Sex, n (%)
  Male 74 (60.7) 65 (53.3) 145 (48.2)
  Female 48 (29.3) 57 (46.7) 156 (51.8)
Presence of underlying disease 59 (48.4) 53 (43.4) 96 (31.9) 0.005‡‡
Unknown underlying disease 0 (0) 0 (0) 17 (5.6)

Characteristics of definitions of close contacts and infection and attack rates in four Asian countries.

Time Distance Protective measure* Observation period Secondary infection rate Secondary attack rate

<2.0 m <1.0 m
Taiwan 15 min or more (conversing) ○ (medical institution) None (medical institution) Jan – Apr 2020 0.8% 0.7%
Singapore 30 min (with patient) - Jan – Apr 2020 - 2.4%
Guangzhou, China None (social life) Jan – Mar 2020 3.7% 3.5%
Guangzhou, China None (social life) Before March 2020 - 4.4%
Hubei Province, China None (social life) Jan – Feb 2020 - 6.5%
Nagano, Japan 15 min or more (contact) None (social life) Aug – Sep 2020 - 15.0%
Our study Had prolonged contact None (social life) Mar – Jun 2020 Period 1:13.3% -
Fukui, Japan 15 minutes or more (contact) None (social life) Jul – Sep 2020Oct 2020 – Feb 2021 Period 2:19.2%Period 3:20.0% --

Odds ratios of having a positive SARs-CoV-2 test result among close contacts of patients with COVID-19.

Period Close contact with COVID-19 patient SARS-CoV-2 test Stratified independence test (Pearson's χ2 test) Stratified odds ratio


Positive Negative Odds ratio 95% confidence interval Lower-Upper
1* No, n (%) 65 (2.2) 2866 P < 0.0001 6.76 4.66–9.80
Yes, n (%) 57 (13.3) 372
2 No, n (%) 66 (1.1) 6011 P < 0.0001 21.70 14.85–31.71
Yes, n (%) 56 (19.2) 235
3 No, n (%) 147 (0.7) 21596 P < 0.0001 36.90 29.04–46.91
Yes, n (%) 154 (20.0) 613

Number of close contacts and SARS-CoV-2 positivity rate among close contacts patients with COVID-19 in Fukui Prefecture, Japan.

Period 1* Period 2 Period 3 P
Number of close contacts 429 291 767
Positivity rate among close contacts, n (%) 57 (13.3) 56 (19.2) 154 (20.0) 0.009
eISSN:
1875-855X
Language:
English
Publication timeframe:
6 times per year
Journal Subjects:
Medicine, Assistive Professions, Nursing, Basic Medical Science, other, Clinical Medicine