The AY.33 sub-lineage of the delta variant might not be readily detectable with current PCR or rapid antigen tests. These can be updated, but in the interim, cases may go undetected.

This is one reason why Australia’s plan to end hotel or home quarantine is premature.
This isn’t the first time variants have caused testing issues. One of the reasons the alpha variant was noticed was because tests for the spike gene returned false negatives.

Fortunately, the tests also looked for other parts of the virus, which had not changed significantly.
A variant also emerged in France that was difficult to detect. Viral loads in the upper (but not lower) respiratory tract were often below the detectable limit in people infected with the B.1.616 variant.
medrxiv.org/content/10.110…
It’s unclear what’s happening here with the AY.33 variant. Perhaps it’s a false alarm.

Nonetheless, this demonstrates the importance of staying at home (unless seeking medical attention or getting a test) any time people have symptoms suggestive of COVID-19.

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More from @DrZoeHyde

23 Oct
Do you know what’s really funny? I’ve published more on geriatrics than @DrKGregorevic.

And while *I* have published papers on cognitive impairment and dementia, I can’t find a single paper on that subject by Dr Gregorevic in PubMed.
For example, not long ago, I published:

Incidence and predictors of cognitive impairment and dementia in Aboriginal Australians: A follow-up study of 5 years
alz-journals.onlinelibrary.wiley.com/doi/10.1016/j.…

And one of the projects I’m currently working on is a cluster RCT to improve dementia detection.
It’s interesting that when people don’t like me talking about the science of COVID-19, they resort to using ad hominem attacks.

And not particularly good ones, either.
Read 4 tweets
18 Oct
Long COVID is real, and we need to protect children from it. In Israel, long COVID clinics for children are busy. The clinic at the Schneider Children’s Medical Center in Petah Tikva has about 150 patients and hundreds more are waiting for treatment. 🧵
haaretz.com/israel-news/th…
Liat Ashkenazi-Hoffnung, a clinic doctor says that in some children long COVID "appears as a direct continuation of severe illness but in very many of the children, there is a severe illness, followed by a lull of several months and only then do the symptoms of long COVID begin."
Many children fully recover, but it can take time.

Ashkenazi-Hoffnung says "we had a boy here who was a competitive swimmer and came down with long COVID and was very anxious and in pain. After half a year he went back to swimming and even broke a personal record."
Read 14 tweets
14 Oct
A new study of weekly testing of children and staff at a Belgian primary school shows what we’ve always suspected: if mitigation measures aren’t in place, transmission is common between children and adults at school, and it spills over into households.
jamanetwork.com/journals/jaman…
In this study, the researchers found:

✅ adult-to-adult transmission
✅ adult-to-child transmission
✅ child-to-adult transmission
✅ child-to-child transmission
The researchers found that the virus readily spread from the school into households.

Teachers infected their partners, and children infected their parents.
Read 4 tweets
29 Sep
Although there are issues with waning immunity, current COVID-19 vaccines offer excellent protection. But this might not always be the case. Future variant-specific boosters may preferentially boost responses to the original strain and be less effective.🧵
cell.com/trends/immunol…
The theory works like this: a person exposed to strain A of the virus (either by vaccination or infection) may prime their immune system such that the ability to make future antibodies specific to a future strain (strain B) is reduced.

This is known as immune imprinting.
In that scenario, a vaccine booster for strain B will give some protection against the new strain B, but the immune system will preferentially produce antibodies against the original strain A.

In certain situations, this has the potential to be harmful.
en.m.wikipedia.org/wiki/Original_…
Read 11 tweets
21 Sep
Study of people with mild or moderate (but not hospitalised) COVID-19 from the first wave in Geneva. 7-9 months later, at least 25% had >=1 persisting symptom. Most common: fatigue (14%); loss of smell/taste (11%); headache (7%); shortness of breath (8%).
acpjournals.org/doi/10.7326/M2…
Note: These proportions were calculated using the entire study sample as the denominator. However, one-third of people were lost to follow-up and their health status was unknown. It’s therefore possible that the proportion of people experiencing persistent symptoms was higher.
Of those with fatigue, 27% said they were limited in strenuous activity. 60% of those with shortness of breath experienced this when walking up a slight hill or when hurrying. Most people with headache or loss of smell or taste reported at least moderate symptoms.
Read 4 tweets
14 Sep
This is a pre-print, and needs to be interpreted carefully, but if it's correct the implications are concerning.

From about mid-2020, SARS-CoV-2 began to evolve at a faster rate, and is now evolving faster than influenza. Whether this will continue is unclear.
The authors suggest two theories for this, both of which could be true.

First, certain mutations could "unlock" new space for further mutations to occur. This seems quite likely: the virus has only just started to adapt to humans
Second, selection pressure could be driving an increase in mutations. Think of the first wave in Manaus, Brazil, where people thought herd immunity had been reached. A second wave followed, as the virus evaded immunity and got better at infecting people.
Read 5 tweets

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