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One in Three Household Members
Picks Up Virus From Person With COVID-19
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Mark Mascolini
About 1 in 3 household members of a person with SARS-CoV-2 infection also tested positive for the coronavirus in a study of 240 people in Wuhan, China, the original epicenter of the COVID-19 pandemic [1]. The researchers did not analyze virus genetically to see if household members shared the same strain, but strict quarantines at the time of this study suggest it does measure household transmission.
This retrospective case series involved 85 inpatients in Wuhan City, Hubei Province with SARS-CoV-2 infection confirmed by RT-PCR of throat swab samples. All participants entered the hospital on February 13 and 14, 2020. Through February 28, 2020, researchers enrolled members of each infected person’s household, tested them for SARS-CoV-2 with RT-PCR of throat swabs, and collected epidemiologic, demographic, and symptom data.
Wuhan City strictly limited and monitored all traffic starting January 23, 2020. People who had contact with a SARS-CoV-2-infected person were asked to quarantine themselves at home or were taken to quarantine facilities.
The 85 index patients in the hospital with SARS-CoV-2 had 155 household contacts. Of those 155, 47 (30%) had SARS-CoV-2 confirmed by RT-PCR, 57 (37%) tested negative for SARS-CoV-2, and 51 (33%) did not have RT-PCR because they remained asymptomatic for COVID-19 for at least 2 weeks. Sixteen of these untested 51 (31%) had no signs of viral pneumonia on chest computed tomography. Only 2 household contacts (1.3%) had passed the Huanan Seafood Market within 1 month of February 13, 2020, the site linked to the initial clustering of SARS-CoV-2 infections.
Among the 240 total household members, 107 (45%) were men, 115 (48%) were women, and 18 (7%) were children. Sixty-four of 107 men (60%), 66 of 115 women (57%), and 2 of 18 children (11%) had RT-PCR-confirmed SARS-CoV-2 infection.
Assuming that all household infections represented transmissions from the hospitalized index case, the researchers calculated that an average 5.5 days passed between the first infection and the second infection. If a third person in the household became infected, an average 3.0 days passed between the second infection and the third.
The authors noted that the overall 30% household transmission rate for SARS-CoV-2 far exceeds previously reported transmission rates of two other coronavirus infections—10.2% with SARS-CoV [2] and 5% with MERS-CoV [3].
References
1. Wang Z, Ma W, Zheng X, Wu G, Zhang R. Household transmission of SARS-CoV-2. J Infect. 2020, doi: https://doi.org/10.1016/j.jinf.2020.03.040.
2. Wilson-Clark SD, Deeks SL, Gournis E, et al. Household transmission of SARS, 2003. CMAJ. 2006;175:1219-1223.
3. Drosten C, Meyer B, Muller MA, et al. Transmission of MERS-coronavirus in household contacts. N Engl J Med. 2014;371:828-835.
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