Dr Zoë Hyde(1/4) Respiratory viruses are much more likely to spread indoors than outdoors, but outdoor super-spreading events can still occur if the conditions are right.
A new study describes a SARS-CoV-2 outbreak affecting 131 people at a night market. 🧵
(2/4) The outbreak happened when a family of 3 people infected with the omicron BA.5.2 variant visited a night market in Zhejiang Province, China, in July 2022. They spent 1 hour and 4 minutes at the market.
On the evening of the outbreak, it was warm (27 degrees Centigrade), humid, and there was very little wind. Most of the market stalls had big umbrellas and it was crowded. The market had a capacity of 5,000 people.
(3/4) During their 1 hour and 4 minutes at the market, the index cases infected 131 people.
Researchers worked out that infectious aerosols were able to remain suspended in the air for up to 1 hour and 39 minutes.
Why were so many people infected?
👉 Very little breeze
👉 Narrow aisles with umbrellas overhead
👉 2 cases did not wear masks
👉 Cases had to speak loudly due to the noisy environment
(4/4) This study shows that super-spreading events can occur outside if the conditions are right. It’s probably a good idea to continue to wear a mask outside if the environment is crowded.
Link to study: https://www.frontiersin.org/articles/10.3389/fpubh.2023.1153303/full
Analysis of a super-transmission of SARS-CoV-2 omicron variant BA.5.2 in the outdoor night market
IntroductionThe COVID-19 pandemic continues to ravage the world, and mutations of the SARS-CoV-2 continues. The new strain has become more transmissible. The role of aerosol transmission in the pandemic deserves great attention.MethodsIn this observational study, we collected data from market customers and stallholders who had been exposed to the virus in the Qingkou night market on July 31 and were subsequently infected. We analyzed the possible infection zones of secondary cases and aerosol suspension time in ambient air. We described and analyzed the characteristics of the secondary cases and the transmission routes for customers.ResultsThe point source outbreak of COVID-19 in Qingkou night market contained a cluster of 131 secondary cases. In a less-enclosed place like the Qingkou night market, aerosols with BA.5.2 strain released by patients could suspend in ambient air up to 1 h 39 min and still be contagious.ConclusionAerosols with viruses can spread over a relatively long distance and stay in ambient air for a long time in a less enclosed space, but shorter than that under experimental conditions. Therefore, the aerosol suspension time must be considered when identifying and tracing close contact in outbreak investigations.
Kate Nyhan is changing servers@DrZoeHyde
Hey #medlibs scroll up for a fascinating study that could be better indexed with MeSH. https://pubmed.ncbi.nlm.nih.gov/37469696/
Hey #medlibs scroll up for a fascinating study that could be better indexed with MeSH. https://pubmed.ncbi.nlm.nih.gov/37469696/
Analysis of a super-transmission of SARS-CoV-2 omicron variant BA.5.2 in the outdoor night market - PubMed
Aerosols with viruses can spread over a relatively long distance and stay in ambient air for a long time in a less enclosed space, but shorter than that under experimental conditions. Therefore, the aerosol suspension time must be considered when identifying and tracing close contact in outbreak inv …
#medlibs @medlibs The headings that are present are fine.
But what about the heading "Respiratory Aerosols and Droplets"? The authors of this study clearly consider aerosol transmission to be an important aspect of their work. It's in the author keywords 2x and in the abstract repeatedly.
Maybe MTIA fails to identify that because "Respiratory Aerosols and Droplets" is a new heading as of 2022? But it was broken off from the long-existing term "Aerosols," presumably in the MTIA training data....
But what about the heading "Respiratory Aerosols and Droplets"? The authors of this study clearly consider aerosol transmission to be an important aspect of their work. It's in the author keywords 2x and in the abstract repeatedly.
Maybe MTIA fails to identify that because "Respiratory Aerosols and Droplets" is a new heading as of 2022? But it was broken off from the long-existing term "Aerosols," presumably in the MTIA training data....
@medlibs
And the fact that there is no MeSH for outbreak investigation - well, there is "Disease Outbreaks" but that is defined as "Sudden increase in the incidence of a disease. The concept includes EPIDEMICS and PANDEMICS." It's not specifically about outbreak investigation or case investigation. Seems like an important gap in this controlled vocabulary.
And the fact that there is no MeSH for outbreak investigation - well, there is "Disease Outbreaks" but that is defined as "Sudden increase in the incidence of a disease. The concept includes EPIDEMICS and PANDEMICS." It's not specifically about outbreak investigation or case investigation. Seems like an important gap in this controlled vocabulary.
Jonathan"39 minutes" is a very optimistic impression of significant values hah
Danu@DrZoeHyde wait, so the other 129 infected wore masks? What kind of, no n95/ffp2 I guess?