Marc Johnson Profile picture
Jul 9, 2025 10 tweets 4 min read Read on X
I've always found this frustrating.

You or your child has a respiratory infection. It's not flu or COVID. Your doctor can only tell you, 'you have a virus'.

Could it be a little bit more specific?

We hope to help answer this question, non-invasively, and for free.
1/ Image
Contrary to my prior assumptions, many of the most common pathogens are not everywhere, all the time. They occur in discrete waves, often nationwide.

I wrote about this recently with Rhinoviruses, the most frequent cause of the common cold.

2/
As promised, we've now added a standalone readout of the rhinoviruses on our wastewater dashboard.

3/
lungfish-science.github.io/wastewater-das…Image
We debated how to best display this. There are over 100 rhinovirus serotypes, and we wanted to display their prevalence over space and time. Too many dimensions.

This was our first stab at it.

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First, we only listed the serotypes that have appeared in at least 4 consecutive samples.

They are ordered based on when they first appeared in 4 consecutive samples.

Time goes left to right, starting in 2024. Larger circles mean more of that serotype detected.
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In the legend you can toggle the different sewersheds we are reporting (hopefully adding more soon).

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The rhinoviruses have been most prevalent in late Spring, and most of the prevalent serotypes in Columbia last year are not prevalent this year.
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And if you look at the other locations, most of the serotypes prevalent in Columbia this year were prevalent everywhere.
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This is fascinating. Although the rhinoviruses were usually surging in Spring, there was an outbreak of C42 in Fall of last year and it occurred in every one of the sewersheds coast-to-coast.

Who knew?
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That's it for now. We continue to recruit more sewersheds in partnership with @SecureBio.

More updates to come.

10/10

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More from @SolidEvidence

Jun 10
I’m so excited. My secret (not so secret) observational experiment is about to begin.

This is a once in a lifetime opportunity for wastewater surveillance.

FIFA World cup.
1/
@SecureBio
scientificamerican.com/article/the-wo…
Starting this week, over 5 million international visitors from at least 48 countries will be descending on 16 cities in North America.
The average visitor will stay 1-3 weeks.
2/
Distribution will not be random. Teams will generally play each of their games in a different city, and their international fans will presumably move in mass with them.
3/ Image
Read 7 tweets
Apr 30
This is crazy.

Imagine a hole the size of a football field that is 700 feet deep.

Now fill it up with wastewater, and remove a tablespoon.

That was our starting material for this study.

1/ Image
Using an untargeted sequencing approach, we were not only able to identify a single measles patient from that sample, but we were able to confirm that the sequence of the virus specifically matched the virus from that patient.

2/
evidence.nejm.org/doi/pdf/10.105…
Kind of mind boggling, isn’t it?

3/3
Read 4 tweets
Apr 28
BA.3.2 is strange is so many ways.

It's now 17 months old, which is really quite old for a COVID lineage.

Every so often there is a sweeping lineage that displaces everything in circulation, but when that doesn't happen the existing 'clans' fight it out with each other.
1/
The longest running clan is the current one. BA.2.86 emerged around July 2023 and is still going strong.

This is the RBD of the original BA.2.86, and some of its descendants from 17 months later.

2/ Image
The second longest lasting was the XBB clan. It emerged around August of 2022 and lasted until early 2024.

Again, here is the original RBD and the RBDs 17 months later.

3/ Image
Read 5 tweets
Apr 4
I’m amazed.
It’s really true: the BA.3.2 COVID lineage is infecting children at a much higher rate than previous lineages.

I’m late to this party, but I couldn’t really believe it was true until I did the analysis for myself.
1/
Most countries do not include patient ages with the sequence, so I restricted my analysis to

1. countries with reliable age info,
2. only included sequences submitted since Dec 2025
3. only included countries with over 50 BA.3.2 sequences.

2/
The country with the most BA.3.2 seqs was Luxembourg.

The fraction of BA.3.2 sequences there coming from kids under 10 was over 4-times higher than the non-BA.3.2 sequences.
3/ Image
Read 10 tweets
Mar 23
A new cryptic lineage popped up in St Louis a few weeks ago.

I’ve been sampling this sewershed (500k people) twice a week for years and the first time I see this cryptic lineage it is 5 years old and makes up 50% of the sample.
1/ Image
I believe the cryptic is a B.1.1 (circulated until early 2021), but it’s possibly even a B.1.
Clearly pre-Omicron though.
2/ Image
The genome is ridiculously predictable.
At least part of the sequences had s2m intact with the 29758G fix.

3/ Image
Read 9 tweets
Jan 24
We found a new (I think) cryptic lineage this week.
I know I say this all the time, but this is really weird.
Warning, this thread is for nerds only.
1/
Here’s what we do. Every week we download all of the new sequences from SRA and run a bunch of screens to look for anachronistic or cryptic lineages.

This new one popped up in 3 different screens.
2/
A good way to spot anachronistic lineages is to look for sequences that have been deleted in contemporary lineages. The virus can only undo a deletion through recombination. If we find seqs that lack the deletions, they have to be old (or contaminated with something old).
3/
Read 16 tweets

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