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Volume 27, Number 3—March 2021
Dispatch

Familial Clusters of Coronavirus Disease in 10 Prefectures, Japan, February−May 2020

Reiko MiyaharaComments to Author , Naho Tsuchiya, Ikkoh Yasuda, Yura K. Ko, Yuki Furuse, Eiichiro Sando, Shohei Nagata, Tadatsugu Imamura, Mayuko Saito, Konosuke Morimoto, Takeaki Imamura, Yugo Shobugawa, Hiroshi Nishiura, Motoi Suzuki, and Hitoshi Oshitani
Author affiliations: National Center for Global Health and Medicine, Tokyo, Japan (R. Miyahara); National Institute of Infectious Diseases, Tokyo (R. Miyahara, M. Suzuki); Tohoku University, Miyagi, Japan (N. Tsuchiya, Y.K. Ko, S. Nagata, T. Imamura, M. Saito, H. Oshitani); Nagasaki University, Nagasaki, Japan (I. Yasuda, E. Sando, K. Morimoto); Kyoto University, Kyoto, Japan (Y. Furuse, H. Nishiura)

Main Article

Table 1

Characteristics of primary and secondary case-patients in households of familial clusters of coronavirus disease in 10 prefectures, Japan, February−May, 2020*

Characteristic Primary Secondary
No. case-patients
 306
 147
Sex
F 152 (49.7) 82 (55.8)
M 153 (50.0) 64 (43.5)
Unknown
 1 (0.3)
 1 (0.7)
Age, y
0–19 11 (3.5) 28 (19.0)
20–29 48 (15.7) 14 (9.5)
30–39 36 (11.8) 16 (10.9)
40–49 58 (19.0) 8 (5.4)
50–59 57 (18.6) 24 (16.3)
60–69 43 (14.1) 29 (19.7)
70–79 31 (10.1) 14 (9.5)
>80 22 (7.2) 14 (9.5)
Unknown
 0 (0)
 1 (0.7)
Contact history to COVID-19 nonfamilial cases
No 146 (47.7) 147 (100)
Yes 159 (52) 0
Unknown
 1 (0.3)
 0
Symptom
Symptomatic 271 (88.6) 103 (70.1)
Asymptomatic 28 (9.2) 39 (26.5)
Unknown
 7 (2.3)
 5 (3.4)
Median time from symptom onset to diagnosis, d (IQR)
 6 (4–9)
 5 (2.5–9)
Confirmed date of primary case
On or before April 16 179 (58.5) NA
After April 16
 127 (41.5)
 NA
Policy of testing for asymptomatic contacts
No testing, 2 prefectures 54 (17.6) 16 (10.9)
Testing for asymptomatic contacts, 8 prefectures
 252 (82.4)
 131 (89.1)
*Values are no. (%) unless otherwise indicated. COVID-19, coronavirus disease; IQR, interquartile range; NA, not applicable.

Main Article

Page created: December 29, 2020
Page updated: February 21, 2021
Page reviewed: February 21, 2021
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