(1/4) Case-control study of 1,050 contacts of #COVID19 cases in 3 clusters in Thailand, showing that wearing a mask was associated with reduced risk of becoming infected.

The type of mask worn did not matter, but it did have to be worn consistently.
wwwnc.cdc.gov/eid/article/26…
(2/4) Physical distancing, shorter contact duration, hand washing, and wearing a mask always when in contact with a case (but not just sometimes) was associated with reduced risk of becoming infected.

Sharing dishes, cups, and cigarettes was associated with increased risk.
(3/4) Wearing a mask was not associated with a false sense of security.

People who wore a mask were more likely to maintain physical distance and to practice hand hygiene than those who did not wear a mask.
(4/4) The authors noted that "no single protective measure was associated with complete protection from COVID-19. All measures, including mask-wearing, handwashing, and social distancing, can increase protection against COVID-19 in public settings."

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More from @DrZoeHyde

30 Sep
(1/4) Study of #SARSCoV2 transmission on a 5-hour flight from Sydney to Perth. There were 11 people considered infectious on board. Eight probable & 3 possible secondary cases resulted from the flight. 27% sat more than 2 rows away, & 64% had window seats.
wwwnc.cdc.gov/eid/article/26… Image
(2/4) Two of the secondary cases who sat in window seats never left their seat during the flight. This, and the fact that 27% of secondary cases sat more than 2 rows away from index cases suggests aerosol transmission may have occurred.
(3/4) Index cases didn’t seem equally infectious, and transmission was only detected in the mid cabin. No secondary cases were detected in passengers sitting in the aft cabin, despite infectious passengers being in this area. This raises the possibility of a superspreading event.
Read 4 tweets
29 Sep
(1/7) Study of #COVID19 in US children. 277,285 cases were reported between 1 March and 19 September. Incidence higher in adolescents compared to young children (although more adolescents were tested). 1.2% were hospitalised (0.1% ICU), and 0.02% died.
cdc.gov/mmwr/volumes/6… Image
(2/7) The overall average weekly incidence was as follows:

Ages 5-11 years:
19 cases per 100,000 persons

Ages 12-17 years:
37 cases per 100,000 persons

However, more older children were tested than younger children. Image
(3/7) Overall, adolescents were more likely to test positive than younger children, but this was not the case in all regions.

In some regions, there was no difference in the proportion of younger and older children testing positive. ImageImageImageImage
Read 7 tweets
24 Sep
(1/4) More on the recent reinfection cases from India. Two papers (one of which is a pre-print) describe the cases.

An insufficient antibody response might explain at least some of the cases, which were mild or asymptomatic the first time.

H/T: @vinodscaria and @swapneilparikh.
(2/4) In the first study, cases were detected in two healthcare workers during routine surveillance.

The workers were asymptomatic for both infections, which were 108 and 111 days apart.

Viral loads were higher the second time.
academic.oup.com/cid/advance-ar…
(3/4) In the second paper, 4 cases in healthcare workers are described.

The cases were mild or asymptomatic the first time, and marginally worse the second time with longer illness.

The interval between the infections was 16, 53, 63, and 65 days.
papers.ssrn.com/sol3/papers.cf…
Read 4 tweets
19 Sep
(1/4) Pre-print study (interpret cautiously), suggesting lower observed incidence of #SARSCoV2 infection in children and adolescents reflects lower testing, rather than reduced susceptibility. The figure shows observed (red) and adjusted incidence (blue).
medrxiv.org/content/10.110…
(2/4) After adjusting for testing frequency, Canadian children aged >=10 years were found to be infected at a similar rate to adults.

Adjusted incidence was also higher in younger children, although it remained lower than that of the population as a whole.
(3/4) However, this could still reflect under-testing rather than reduced susceptibility. Cases in younger children are hard to detect because symptoms can be non-specific, and asymptomatic infection is common.

Younger children may also have been shielded more than adolescents.
Read 4 tweets
17 Sep
(1/4) Study of #COVID19 in Hong Kong from January to April, showing that the epidemic was characterised by superspreading events. Just 19% of infections were responsible for 80% of secondary cases, and 69% of people did not infect anyone.
nature.com/articles/s4159…
(2/4) However, interventions in place included school closures, some people working from home, bans of mass gatherings, and near-universal mask wearing.

Had these interventions not been in place, even more superspreading may have occurred.
(3/4) The majority of cases (51%) were linked to one of 137 clusters. The largest cluster (106 cases) was associated with 4 bars, the 2nd largest (22 cases) to a wedding, and the 3rd largest (19 cases) to a temple.

Musicians are thought to have spread the virus between the bars.
Read 4 tweets
12 Sep
(1/12) Study of #SARSCoV2 transmission by children. 12 children infected in childcare transmitted the virus to at least 12 of 46 (26%) contacts at home or in the community. One parent was hospitalised. Transmission by 2 of 3 asymptomatic children was seen.
cdc.gov/mmwr/volumes/6…
(2/12) This was a retrospective study of outbreaks that occurred at 3 childcare centres.

The index cases in all 3 clusters were staff members. Two of the 3 staff had a household contact with confirmed or probable #COVID19, and had gone to work while this person was symptomatic.
(3/12) A total of 22 #COVID19 cases were reported at the 3 childcare centres. Twelve cases (54%) were in children.
Read 12 tweets

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