Evidence for lack of transmission by close contact and surface touch in a restaurant outbreak of COVID-19

Abstract

Background: Coronavirus disease 2019 (COVID-19) is primarily a respiratory disease that has become a global pandemic. Close contact plays an important role in infection spread, while fomite may also be a possible transmission route. Research during the COVID-19 pandemic has identified long-range airborne transmission as one of the important transmission routes although lack solid evidence. Methods: We examined video data related to a restaurant associated COVID-19 outbreak in Guangzhou. We observed more than 40,000 surface touches and 13,000 episodes of close contacts in the restaurant during the entire lunch duration. These data allowed us to analyse infection risk via both the fomite and close contact routes. Results: There is no significant correlation between the infection risk via both fomite and close contact routes among those who were not family members of the index case. We can thus rule out virus transmission via fomite contact and interpersonal close contact routes in the Guangzhou restaurant outbreak. The absence of a fomite route agrees with the COVID-19 literature. Conclusions: These results provide indirect evidence for the long-range airborne route dominating SARS-CoV-2 transmission in the restaurant. We note that the restaurant was poorly ventilated, allowing for increasing airborne SARS-CoV-2 concentration.

Outbreak investigation of airborne transmission of Omicron (B.1.1.529) - SARS-CoV-2 variant of concern in a restaurant: Implication for enhancement of indoor air dilution

“…In outbreak R2 and R1, the estimated quanta generation rate was 1023.4 h -1 and 557.6 h -1 , respectively, which is much higher than the estimated quanta generation rate of 79.3 h -1 in a restaurant outbreak, and 35.0 h -1 and 58.3 h -1 in a two buses outbreak in early 2020. Li et al, (2021 ; Zhang et al, 2021 ; Chau et al, 2021 ; Lam et al, 2020 ; Li et al, 2021 ; Ou et al, 2022) Although the quanta generation rate for the Omicron variant in R2 is 83.5% larger than that for the non-Omicron variant in R1, the secondary attack rate is much lower in R2 (3.4%) than in R1 (28.9%), suggesting that enhancement of indoor air dilution may mitigate the SARS-CoV-2 transmission.…”

“… Tang et al, (2021 ; Morawska et al, 2020 ; Conte et al, 2021) Dining places and bars were considered as the high-risk area for COVID-19 outbreaks as people may interact closely without wearing masks. Li et al, (2021 ; Zhang et al, 2021 ; Chau et al, 2021) In fact, social gathering with mask-off activities has been shown to increase the risk of SARS-CoV-2 transmission during the early phase of COVID-19 pandemic. Cheng et al, (2020) In Hong Kong, the first community outbreak of COVID-19 with superspreading event was attributed to the family gathering and dining in a commercial party room.…”

Weakening personal protective behavior by Chinese university students after COVID-19 vaccination

“…In our study, 97.0% and 89.3% of the students respectively believed that large droplet and short-range airborne transmission were possible SARS-CoV-2 transmission routes. Although some studies of indoor outbreaks have shown that long-range airborne transmission is a dominant route, especially in settings with poor ventilation [ 30 , 31 ], only 24.1% of the students believed that this was a possible route of SARS-CoV-2 transmission. The evidence has increasingly demonstrated that fomite transmission plays an insignificant role in the COVID-19 pandemic [ 32 ]; however, 50.9% and 36.0% of the students believed that SARS-CoV-2 could be transmitted via the short-range and long-range fomite routes, respectively.…”

COVID-19 Vaccination Did Not Change the Personal Protective Behaviors of Healthcare Workers in China

“…In our study, 98.0 and 91.8% of 1,499 HCWs believed that large-droplet and short-range airborne transmission, respectively, were possible SARS-CoV-2 transmission routes. Although some studies of indoor outbreaks have shown that long-range airborne transmission is a dominant route, especially in settings with poor ventilation (23,24), only 20.0% (300/1,499) of the HCWs believed that this was a possible route of SARS-CoV-2 transmission. Accumulating evidence has demonstrated that fomite transmission plays an insignificant role in SARS-CoV-2 transmission (25, 26); however, 66.5% (997/1,499) and 43.0% (645/1,499) of that HCWs believed that SARS-CoV-2 could be transmitted via the short-range and long-range fomite routes, respectively.…”