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Transmissibility of SARS-CoV-2 High Within Households

No significant difference in infectivity seen for incubation period versus symptomatic period

MONDAY, June 22, 2020 (HealthDay News) -- Severe acute respiratory syndrome coronavirus 2 has high transmissibility within households, according to a study published online June 17 in The Lancet Infectious Diseases.

Qin-Long Jing, Ph.D., from the Guangzhou Center for Disease Control and Prevention in China, and colleagues estimated the secondary attack rate of COVID-19, defined as the probability that an infected individual will transmit the disease to susceptible individuals among household and nonhousehold contacts. One hundred ninety-five unrelated close contact groups (215 primary cases, 134 secondary or tertiary cases, and 1,964 uninfected close contacts) were traced between Jan. 7 and Feb. 18, 2020.

The researchers found that the estimated secondary attack rate among household contacts was 12.4 percent when household contacts were defined as close relatives and 17.1 percent when household contacts were defined on the basis of their residential address, assuming a mean incubation period of five days, a maximum infectious period of 13 days, and no case isolation. The risk for household infection was lower in the youngest age group (<20 years) and for those aged 20 to 59 years compared with the oldest age group (≥ 60 years; odds ratios, 0.23 [95 percent confidence interval, 0.11 to 0.46] and 0.64 [95 percent confidence interval, 0.43 to 0.97], respectively). Greater infectivity was suggested during the incubation period than the symptomatic period, although the differences were not statistically significant (odds ratio, 0.61; 95 percent confidence interval, 0.27 to 1.38).

"The infectiousness of patients with COVID-19 during their incubation periods is high and could substantially increase the difficulty of curbing the ongoing pandemic," the authors write.

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