How do we survive next 6-12 months?
Tweets by @TinaG_SD epitomize what many feel - even w/ relatively good measures in place, as in CA (mask mandate, bars/restaurants closed or nearly so, sick pay, etc.), transmission continues & cases ebb & flow & restrictions crush jobs.
Thread
COVID cases are surging in many parts of the US now where there are few measures in place (no mask mandates, open bars, etc.).

These measures certainly help but don't seem to be enough (see previous tweet). Why?
Transmission of COVID-19 is inherently a 2 step process. Step 1: Transmission w/in households is rapid with whole households sometimes getting infected.
Step 2: Transmission between households.
Transmission w/in households is hard to stop b/c few wear masks at home & we sleep, eat, drink, talk with household members. It's actually surprising that household attack rates aren't higher (~20%; Z Madewell @nataliexdean medrxiv.org/content/10.110…)
So the key to stopping transmission is stopping b/w household transmission.
Where does this transmission occur? Some of it happens in work settings, & masks, distance help reduce that. Some happens in bars, restaurants, etc. & closing those reduces this.
Some transmission happens b/c people go to work when they are mildly ill b/c they might not get paid or will get penalized for missing work. Sick pay & incentives to encourage staying home & getting tested help with this.
We need all these things - masks, sick pay, safe isolation/quarantine space, safe work spaces w/ distance, ventilation, etc. But they aren't enough because...
Quite a bit of b/w household transmission happens at private social gatherings that closing businesses & making work places safer don't stop, including both big events like weddings (theguardian.com/us-news/2020/s…) & also smaller gatherings - meeting a friend or driving together.
Stopping this kind of transmission requires people to know risk & make choices to gather safely. This means meeting outside w/ 6' distance or masks or both. But if people discount risk (e.g. due to Trump/Fox news misinformation), then they think hassle is too big & meet inside.
Also, if it's easy to meet safely then people are more likely to do it. Thus, closing the safest public places (parks, beaches) is harmful & worst for poorest that don't have private outdoor space, especially in cities. @zeynep @JuliaLMarcus
Many of us are worried about winter coming because outside is less fun when it is 0C, resulting in less safe indoor gatherings b/w friends & family. Many places, including CA, have closed outdoor safe spaces & made no effort to create safe places/ways for people to gather.
They have resorted to abstinence-only approaches by banning gatherings of all sizes. While we need people to avoid close contact w/ non-household members, humans are social beings & are going to gather. We just need to do it safely.
We obviously can also reduce transmission through testing/tracing/isolate/quarantine: need people to get tested at 1st mild symptoms, get results quick, & need tracing capacity as we showed recently:
medrxiv.org/content/10.110…
For this we need sick pay, easy testing & quick results & sufficient contact tracing capacity & safe isolation/quarantine space.
Until that's all in place, we are relying on measures described above plus personal choices. Poor options, misinformation & fatigue don't help.
To keep transmission low for next 6-12 months before vaccine widely available, we need good information & messaging, good governance, & community wide effort. Sadly we haven't had most of those things due to politics & division & poor leadership when we needed it most.
I've been writing about this for months. Here's a version from June that I wish was outdated:
. Sadly it all still applies. That's how little progress we've made. It's disheartening.
But we can always start now. We have so much to gain. Let's do it!
This provides strong evidence for the need to get accurate information into everyone's hands but especially those getting news from Republican leaning sources.

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More from @DiseaseEcology

5 Oct
CDC's updated webpage on how COVID-19 is spread & prevention tips is now (almost) in line with science!
(WHO please do the same!)

(Hooray! only 10 months into epidemic & when Trump in hospital so maybe isn't paying attention?)
Thread
cdc.gov/coronavirus/20…
Webpage 1st summarizes dominant mode of transmission which is consistent with epidemiology data: mostly from people w/in 6' of each other & clearly states that people w/out symptoms (pre-symptomatic or asymptomatic) can transmit also!
2. Website give ranking of how easily SARS-CoV-2/COVID-19 spreads relative to flu and measles.
(I'm not sure this is supported by data. R0 is higher than flu, but might be due to length of infectious period, not higher infectiousness. Anyone know of data to support/refute?)
Read 10 tweets
3 Oct
PSA: We (STILL) have no data to know the pattern of viral loads over time from infection to recovery. So we don't know how test sensitivity & infectiousness correlate.

Tons of stories w/ quotes from top people are not making this clear & it matters.
Clarifying thread
You may have seen this figures showing viral load over time, with thresholds for testing +.
(This one from @michaelmina_lab @DanLarremore paper). Simple & straightforward, right?
Conceptually yes, but what is this figure based on? Is it SARS-CoV-2/COVID-19 data in people? Nope!
This figure is (loosely) based on data from other viruses in people & SARS-CoV-2 in animals. Here's data from macaques (10.1126/science.abc4776) & cats (pnas.org/cgi/doi/10.107…). Looks similar to schematic but not quite identical. Where is the virus-negative period pre-peak?
Read 39 tweets
29 Sep
I posted this thread earlier because there's a serious challenge ahead: now that antigen tests are being used on a huge scale (WHO bought 120M; Abbott is producing ~50M/month), key Q is: what to do w/ result?
CDC says: + antigen test = "presumptive case".
wwwn.cdc.gov/nndss/conditio…
Understandably, this makes some health care professionals uncertain what to do next, especially if confirmatory PCR test takes days to get results back. Do they treat it like a confirmed case, try to get case to isolate & trace their contacts?
If few false +, no problem!
But if false +s are relatively common (even 1-2% would count as relatively common) & antigen tests are used for frequent screening of asymptomatic people, this would lead to large number of isolated/quarantined people, awaiting PCR tests. Here's an example...
Read 8 tweets
29 Sep
Specificity of antigen vs PCR-tests: data needed!
Many are understandably excited about the new rapid antigen tests. But there are a couple issues I haven't seen robust data on. Maybe you can help?
What is specificity of antigen tests vs PCR?
Thread
@michaelmina_lab
EUA (fda.gov/media/141570/d…) for BinaxNOW specificity (1-false +)=98.5% but:
- sample size is tiny (25 people submitting a total of 102 swabs from SYMPTOMATIC patients)
-95% CI (which should incorporate repeat testing & be analyzed as f(days since symptom onset) is: 92%-99.96%.
This means up to 8% (or more, if analysis done properly; totally unknown for asymptomatic people) of + antigen tests could be false +. If that's the case, these tests would be a disaster for screening people without reason to suspect they are infected (e.g. school kids).
Read 5 tweets
24 Sep
Hawaii is lifting quarantine requirement if travelers take 1 test & United is now offering rapid test for flights to Hawaii.
This will miss some infected people traveling to Hawaii as I detailed earlier:

usatoday.com/story/travel/a…
Hawaii is clearly trading off tourism $$ vs risk of infected people coming to Hawaii. However, they could greatly reduce risk further w/ 2nd test (). Testing capacity has been constraint before, but less so w/ new rapid tests United is using.
Having a few more infected people reach Oahu w/out quarantine isn't a huge deal w/ current case # in 100s, but imported cases could make big difference to other islands & if Oahu could reduce cases it would matter there too.
nytimes.com/interactive/20…
Read 4 tweets
24 Sep
Lots of discussion & opinions about human trials to test efficacy of vaccines. They provide key data to answer a Q that normal phase 3 trials can't:
Does the vaccine reduce infectiousness?
However, they have imp. limitations & carry risks.
Thread.
theguardian.com/world/2020/sep…
Vaccines can reduce (mild or severe) disease (), reduce probability of infection, or reduce infectiousness/transmission. WHO criteria include all 3 of these as possible endpoints for vaccine efficacy.
who.int/blueprint/prio…
FDA criteria for efficacy include infection and disease (mild or severe), but nothing about infectiousness. This is problematic b/c we might think a vaccine is ineffective b/c it doesn't stop infection or reduce disease even if it reduces infectiousness enormously.
Read 20 tweets

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