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9 Dec, 30 tweets, 11 min read
1. Updated thread on children & #COVID19, summarising recent research.

Summary: further evidence children and adults are equally susceptible, and similarly likely to transmit. Schools have been a driver of the second wave in Europe, Canada, and elsewhere.
#edutwitter #auspol
2. First, a recap. Given similar exposure, children and adults appear equally susceptible to infection, and also appear to transmit at a similar rate. School transmission has been increasing in many countries.
3. Because children are more likely to be asymptomatic than adults, infections in this age group can be difficult to detect.

I wrote an article about how this has affected some of the research to date, and why we mustn’t overlook schools.
4. Children are often tested less than adults, which has created a perception they are less likely to be infected.

But when antibody tests are used to look for evidence of a past infection, children, teenagers, and adults appear similarly susceptible.
5. In Germany, PCR testing had initially suggested young children were less likely to be infected than teenagers.

But recent antibody testing has showed no difference. It seems young children just weren’t getting tested.
6. But even antibody testing can have problems, because it often looks for a marker of viral replication.

Because children often fight the virus off quickly (which means less viral replication), false negatives may be more likely in children than adults.
7. In this study of a Melbourne family, the children didn’t test positive with either a PCR test or a standard blood antibody test, despite being infected.

But a saliva antibody test was positive, and there was also evidence of a cellular response.
8. It’s unclear whether the children of the Melbourne family were infectious. Such mild cases (where repeated PCR tests are negative) might not be, which is good news.

But in general, children, teenagers, and adults appear to pose a similar transmission risk.
9. The largest contact tracing study published to date suggests even young children transmit at meaningful rates.

Attack rates by age of index case:

0-4: 6.3%
5-17: 7.3%
18-29: 6.5%
30-39: 7.3%
40-49: 8.0%
50-64: 8.2%
65-74: 7.2%
75-84: 8.5%
>=85: 8.1%
10. A prospective study conducted by the CDC also showed children, adolescents, and adults were similarly likely to infect other household members.
11. Most of the children in those studies were probably symptomatic, and it’s not clear if these results apply to asymptomatic children, who might be less likely to transmit.
12. However, at least some asymptomatic children can transmit the virus, as shown in this study.

This outbreak would not have been detected if a symptomatic adult had not been tested.
13. We would therefore expect to see transmission occurring in schools, at least when community transmission is high.

When good records are kept, we see this is clearly occurring.
14. As community transmission has increased, school outbreaks have become common.

Since writing the tweet below (on 4 December), the number of school clusters reported in the media in Germany has now increased to at least 509.
15. Outbreaks in primary schools have been less commonly reported to date (possibly because they have been less likely to occur, or possibly because they are harder to detect).

However, outbreaks do occur in these settings.
16. The differences we have seen for younger children and teenagers may simply reflect the level of community transmission.

Primary and high school students were similarly affected in a region with high levels of community transmission in Belgium.
17. In Austria, a surveillance study of approximately 14,800 students and 1,200 teachers found that a similar proportion of primary and high school students (up to age 15) were infected.
18. Transmission in schools can therefore be expected to contribute to community transmission to some extent.

In Montreal, this may have been significant.
19. Similarly, in Israel, school reopening appeared to play at least some role in accelerating the epidemic there.
20. A role for schools in driving the epidemic is also suggested by data from England.

Infections fell when schools closed for the half-term holidays, and then increased again when schools reopened.
imperial.ac.uk/news/208413/co…
21. Following this, a short lockdown (excluding schools) was introduced in England. Case numbers started to fall, except in children and teenagers, where they continued to increase.

The UK Government continues to maintain masks are unnecessary in schools.
22. Teenagers are now the most frequently infected age group in England.
23. None of this is particularly surprising. This pattern has been observed across many countries.
24. Here, the president of the Robert Koch Institute (the German equivalent of the CDC) explains children can bring the virus to school and infect their peers, who then take the virus back out into the community.
25. The policies in place in many countries are clearly not working. But the solutions are not complex, and have already been identified.
26. Much more detail can be found in these comprehensive guidelines developed by the Harvard T. H. Chan School of Public Health.

➡️ schools.forhealth.org/wp-content/upl…
27. Interventions to protect schools don’t have to be expensive.

The Max Planck Institute for Chemistry has developed a simple aerosol removal system that costs about 200 Euros to make.
28. I’ve summarised a lot of this information in a (hopefully) easy to read article here:
@threadreaderapp unroll this thread for everyone, please.
Here's the unroll.

Summary: further evidence children and adults are equally susceptible to #SARSCoV2, and similarly likely to transmit. Schools have been a driver of the second wave in Europe, Canada, and elsewhere.
threadreaderapp.com/thread/1336612…
#edutwitter #COVID19 #Schools

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More from @DrZoeHyde

Dr Zoë Hyde Profile picture
12 Dec
(1/10) Follow-up study of household contacts of people with #COVID19, showing it’s possible to prevent transmission at home.

Daily testing showed some people may not test positive for long. One child was positive for only 2 days. Cases are easily missed.
wwwnc.cdc.gov/eid/article/27…
(2/10) This was a study of 5 households in Utah, conducted by the CDC. Each household had one index case. CDC staff visited each household within 2-4 days of the index cases’ positive test (day 0), for the next 4 days (day 1-4), and 14 days later. Contacts were tested each visit.
(3/10) In 3 of the 5 households, there was no transmission to other household members (0%).

In the other 2 households, all family members were infected (100%).

Overall, 7 of the total 15 contacts were infected (47%).
Read 10 tweets
Dr Zoë Hyde Profile picture
10 Dec
(1/5) Study of a biomarker of blood clots in small blood vessels in 50 children with mild (n=21) & severe (n=11) #COVID19, and MIS-C (n=18).

➡️ Biomarker elevated in all groups.

➡️ Evidence of kidney injury in 10% of mild cases (36% severe, 28% MIS-C).
ashpublications.org/bloodadvances/…
(2/5) The children with mild illness included hospital patients in which #SARSCoV2 had been identified in routine testing before admission (unrelated to #COVID19).

As such, it is possible they may not be representative of mild cases generally.
(3/5) It is unclear what the long-term implications of this study are. It is possible these findings are fully reversible.
Read 5 tweets
Dr Zoë Hyde Profile picture
3 Dec
(1/9) #LongCovid is common. In this study of 180 Faroe Islanders (of whom only 8 were hospitalised), 53% had at least 1 symptom after an average of 4 months (minimum follow-up 45 days).

Fatigue, joint pain, and loss of smell and taste were most common.
academic.oup.com/cid/advance-ar…
(2/9) All 187 people who tested positive for #COVID19 between 3 March and 22 April were invited to participate in this study, and 180 took part. Participants were followed up (by telephone) for 45-215 days (average: 125 days).

The average age was 39 years, and 54% were female.
(3/9) In the initial phase of illness, 8 people (4.4%) were asymptomatic.

At the last assessment, just under half (47%) were symptom-free. One-third (33.3%; n=60) had 1 or 2 symptoms, and 19.4% (n=35) had >=3 symptoms.

Two asymptomatic people subsequently reported symptoms.
Read 10 tweets
Dr Zoë Hyde Profile picture
2 Dec
(1/8) Important study demonstrating “opportunistic airborne” transmission of #SARSCoV2 in just five minutes at a restaurant in South Korea, confirmed by CCTV.

Air conditioning may have enabled infection over a distance of more than 4 metres to occur.
jkms.org/DOIx.php?id=10… Image
(2/8) In this study, #COVID19 was detected in a person (case A) on 17 June.

The investigators discovered case A had visited the same restaurant as a previous confirmed case (case B) on 12 June.

It was determined case B had probably infected case A. Image
(3/8) All the people who came into contact with case B at the restaurant were then tested.

One more case (case C) was detected among these people.

In total, 2 of the 13 people (15%) who had been in the restaurant at the same time as case B were infected.
Read 8 tweets
Dr Zoë Hyde Profile picture
1 Dec
(1/6) Why does superspreading occur?

There are likely many reasons, but one intriguing possibility is some people might be biologically predisposed to release more aerosols when they speak.

This study shows that some people are “speech superemitters.”
nature.com/articles/s4159…
(2/6) First, in this study researchers showed that for everyone, the amount of particles that are released increase with the loudness of speech.

This is why activities such as singing pose a particularly high risk for transmission of #SARSCoV2. Image
(3/6) Researchers then measured the amount of particles released per second when participants pronounced the vowel “A”, and when they read aloud in English.

Participants released between 1 and 14 particles per second. The average number was 4.
Read 6 tweets
Dr Zoë Hyde Profile picture
17 Nov
Study showing that children can be infected with #SARSCoV2, but still test negative.

Two parents infected their 3 children, who tested negative 11 times (NP swab PCR test). Antibody blood tests were also negative, but saliva antibody tests were positive.
nature.com/articles/s4146…
In this study, 2 parents from Melbourne attended an interstate wedding without their children, during which they were infected. They returned home and developed symptoms 3 days later.
Seven days after this, 2 of their 3 children developed symptoms.

The oldest child (male, 9 years) developed respiratory and gastrointestinal symptoms.
Read 16 tweets

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