Risk of Airborne Transmission During Home Isolation: A Modeling Study.

OBJECTIVE: The worldwide pandemic of SARS-CoV-2 and its B.1.1.529 variant, Omicron, remain a threat to health. In Japan, self-isolation in a room at home has been recommended in some prefectures to reduce the burden on hospitals. With the aim of preventing the infection of family members in other rooms, this study quantified the risk of infection by airborne transmission to mask-wearing, non-infected members of the household. METHODS: A mathematical modeling approach was used to estimate the risk of airborne infection. RESULTS: For pre-SARS-CoV-2 variants of concern (VOC), the risk of infection of non-mask-wearing family members had an LN distribution with GM of 0.11, GD of 5.38, and median of 0.11; whereas that of mask-wearing members had an LN distribution with GM of 0.05, GD of 5.46, and median of 0.05. For Delta variant, the risk of infection of non-mask-wearing family members had an LN distribution with GM of 0.39, GD of 76.30, and median of 0.40, and that of mask-wearing members had an LN distribution with GM of 0.18, GD of 76.30, and median of 0.18. The difference of these medians was 0.22, which suggests that family members wearing masks is effective for preventing infection, even for highly infectious variants.

Prediction of Potential Respiratory Tract Infection from SARS-CoV-2 Through Hand-to-face Contact Transmission.

OBJECTIVE: The Ministry of Health of China reported a cluster of severe pneumonia cases of unknown etiology in Wuhan city, the cause of which was later identified as a novel coronavirus. However, the risk of infection through indirect transmission routes remains unclear. METHODS: A mathematical modeling approach was used to estimate the risk of infection through hand-to-face contact. The probability of infection for various routes of transmission through face-touching behavior was then calculated. RESULTS: The probabilities of infection through hand-to-mouth transmission from nonporous and porous environments had log-normal (LN) distributions with geometric means (GMs) of 0.0116 and 0.0002, geometric deviations (GDs) of 2.9822 and 3.5560, and medians of 0.0127 and 0.0002, respectively, while those through hand-to-nose transmission from nonporous and porous environments had LN distributions with GMs of 0.0006 and 0.0000, GDs of 43.2310 and 47.3372, and medians of 0.0009 and 0.0000, respectively. The probability of infection through hand-to-eye transmission from a nonporous environment had a beta distribution with α = 2.38803, ß = 13.60457, a minimum of 0.0045, a maximum of 0.9021, and a median of 0.1179, while that from a porous environment had a Weibull distribution with a scale parameter of 0.0030, a shape parameter of 1.323, and a median of 0.0023. CONCLUSION: SARS-CoV-2 infection will occur through hand-to-face contact via contaminated environment.