Finally--A Simple Way to Know If You Are Contagious

Wow, I finally found an answer to a question I have had for months: are antigen tests REALLY a good measure of infectiousness? We know that a negative antigen test is poor at accurately telling if you have covid-19 (false negatives about a third of the time), but what really counts for covid-free group gatherings is not if people have some level of the disease, but are they CONTAGIOUS TODAY?

I found one study (from March 2022) that concluded they are EXCELLENT at this. It said "Interestingly, SARS-CoV-2 contagiousness is highly unlikely with a negative antigen test since it exhibited a negative predictive value of 99.9% compared to viral culture. … Thus, screening people with antigen testing is a good approach to prevent SARS-CoV-2 contagion …"

I think this means that if you do a proper job with a single antigen test, and get a negative result, this DOES reliably say that you are almost certainly not infectious to others. Therefore, the number of contagious people at a gathering apparently can be reduced to near zero if everyone does an antigen test upon or just prior to arrival.

Of course, this is not quite perfect, as in the morning someone could be in the beginning stages of a covid-19 infection, with their virus load increasing but just below the threshold for being significantly infectious, and by the end of the day could be testing positive and starting to be contagious.

But that small level of risk can be easily managed by proper levels of fresh air ventilation and, if needed, supplemental air purification, both of which I expect will scrub the virus out of the air as fast as it’s being introduced by only a very small percentage of people.

I don’t understand why this news has not been "trumpeted from the treetops”! Am I missing something here? So I had an email exchange with the corresponding author of the study. Here’s what he said:

From: Wbeimar Aguilar <wbeimar.aguilar@udea.edu.co>
Subject: Re: antigen test study
Date: August 4, 2022 at 9:17:57 AM EDT

Dear Roy

I totally agree with you and the blog contents you plan to share.

Our conclusion is wordy to be scientifically precise, but it is true; the simple interpretation of the
conclusion is just a negative antigen test = not contagious.

Regards, Wbeimar

Wbeimar Aguilar Jiménez
Biologist, MSc, PhD in Biomedical Sciences
Grupo Inmunovirología
Sede de Investigación Universitaria
Universidad de Antioquia
Medellín-Colombia

Here is the link to his group’s study: https://journals.asm.org/doi/10.1128/spectrum.01962-21

[The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.]

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Someone in the Room Has COVID-19

The overall increase of cases, hospitalizations, and deaths continues. A month ago, the daily U.S. figures were about 30,000 hospitalizations and 300 deaths. Now we are at 40,000 and 400—so approaching 150,000 deaths a year at this rate! Maybe this is the new way, but I sure wouldn’t call it normal. From the Washington Post:

Immunity from a recent infection does not last very long. Australia is figuring that the protective window of prior infection is 28 days. Of course not always exactly, but that’s the early end of the bell curve. After that, with any symptoms, you need to take a covid-19 test right away in order to protect those around you.

https://scroll.in/article/1028215/covid-19-reinfections-are-happening-sooner-than-expected-as-the-virus-evolves-continually

How does all this translate this into your daily life? Just realize that there are a LOT of infected and infectious people around—who don’t realize they are sick.

At one hospital, they made a calculation based on their admissions. “At UC San Francisco’s hospitals, 5.7% of asymptomatic patients are testing positive for the coronavirus, meaning 1 in 18 people who feel fine nonetheless have the coronavirus. In other words, in a group of 100 people, there’s a 99.7% chance that someone there has the coronavirus and is potentially contagious. ‘Think about that the next time you go into a crowded bar or or get onto an airplane with 100 people,’ said Dr. Robert Wachter, chair of the UC San Francisco Department of Medicine.”

Every airplane flight will have infected people and thus some amount of virus in the air. So will every large, indoor group. Know this, and choose where you go, how long you spend there, how good a mask you wear, and what you do to monitor or increase the amount of fresh air ventilation once you get there.

https://www.latimes.com/california/story/2022-07-18/californias-summer-covid-wave-could-top-winter-surge

[The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.]

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(Bad) News Roundup

BA.4 and BA.5 are now dominant

This is an article from Nebraska, but talks about the national covid-19 situation: “Our national COVID-19 case rate is at an 'elevated plateau.' … There are more than 300 deaths per day, and hospitalizations have increased 13% over the last two weeks.” Omicron variants BA.4 and BA.5 are estimated to be two-thirds of the cases nationally. They call it “plateau” but I expect it to be steadily rising all summer. At the current death rate, this would be 100,000 deaths annually.

https://www.nebraskamed.com/COVID/what-covid-19-variants-are-going-around-in-july-2022


We are in a silent surge

We all know a lot of people who have gotten covid-19 lately. Ignore the case counts. Here’s an example of sewage monitoring in California that has reached all-time highs. ‘The sewage never lies.’

https://www.sacbee.com/news/coronavirus/article263044553.html

And I don’t know if this is true, but at least one doctor "estimates 80 percent of infections with Omicron [variants] are actually asymptomatic."

https://archive.ph/JGCdF


"The new omicron variants ... have been shown to be not only more contagious but also capable of causing reinfection.”

And more good info in this article, local to San Francisco but with many national topics.

https://missionlocal.org/2022/07/7-6-22-tracker/


Getting repeat infections is not a good idea

The bottom line seems to be that each new covid-19 infection essentially rolls the dice again with no credit or penalty from the prior infections. Repeat cases are not necessarily the same, or less severe.

The study was for patients in the Veteran Affairs health system, so it is not a representative sample of the U.S. population as a whole. Still, it found that "compared with those with just one Covid-19 infection, those with two or more documented infections had more than twice the risk of dying and three times the risk of being hospitalized within six months of their last infection."

https://www.cnn.com/2022/07/05/health/covid-reinfection-risk/index.html

And from the Washington Post covid-19 newsletter of June 27th:

"Q-How many times can a person ... be infected with Coronavirus after taking both shots of the vaccine and a booster shot?

A-The short answer, unfortunately, is that the number of times a vaccinated and boosted person can get infected is probably limitless."


"Patients With COVID-19 May Have Loss of Taste, Smell for Years After Infection, But Remain Unaware”

One of the many “long covid” effects.

https://www.pharmacytimes.com/view/expert-patients-with-covid-19-may-have-loss-of-taste-smell-for-years-after-infection-but-remain-unaware

[The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.]

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Letters From Readers

June 30th - Adult Summer Camp

Q - My wife and I are registered to attend a week-long, residential adult summer camp in a few weeks, with 50 attendees. The camp leaders are requiring vaccination, testing before arrival and on days 3 and 5, and wearing masks while indoors except when eating. We’re all going to be singing, which I know causes more virus to be exhaled if there is virus present.

What hasn't been discussed, however, is increased safety through good ventilation. I will be bringing my Safetulator Fresh Air (CO2) meter to be able to monitor the inside air quality. What more can be done to minimize our COVID risk, and the risk for everyone?

-Happy Meter User

A - That’s great that you are getting good use from your meter. Here are some suggestions:

(1) The most important thing in general is to realize that—without initial isolation—covid-19 might very well come into the gathering. So, while we can hope for the best, I think it is prudent to plan for the worst. At your location, the current probability per Georgia Tech (https://covid19risk.biosci.gatech.edu/) of having 1+ infected people among a gathering of 50 people is 48%, and for 100 people (at the concert) it is 73%. (These numbers seem low to me, perhaps due to the vast number of uncounted cases.)

(2) To minimize the spread, remember that exposure and risk are cumulative. Our bodies can fend off a certain amount of virus, but once we get overwhelmed, we get sick. So if people can’t do some of these things, don’t give up—still do the ones you can:
- antigen test every day
- symptoms check every day
- rehearsing and dining outside—will they have a tent or a pavilion?
- if rehearsing or dining inside, LOTS of ventilation as you understand
- the concert would best be outside too.

(3) Multiple unrelated people staying together in a single room is increasing the risk, so if there are extra vacant rooms, it would be best to have people spread out as much as possible. Every guest room should have a window fan.

(4) If people test positive or get sick, then either they should go home, or be able to go into on-site quarantine with people to take care of them, and the ability to Zoom in to the rehearsals when they are able to. However, they should not rejoin in person until they have two negative antigen tests, since there is a good chance they will be contagious for the duration of camp (per graph below, as first presented in the June 10th post).

We wish you a safe and enjoyable time at camp!


June 29th - Still Testing Positive

Q - As you know, I’m overseas on an 18-day group singing trip. COVID has invaded our group, including me. No serious cases. Like several others, I took a full day off resting. No singing. Then I’ve had a slight fever and headache, and a gravelly voice. Then I got back to singing softly, so no stress. The afflicted sit in the back of the rehearsal church, and the teacher moves back and forth to coach and answer questions. Unfortunate. But not dire.

But now, I'm still testing positive on rapid antigen tests after 11 days. No symptoms. Now we are doing our multiple concerts. Should I still consider myself contagious?

-Avid Reader

A - I’m sorry covid-19 has found you overseas; I’m happy to hear that there are no serious cases, however.

The CDC says "Positive rapid antigen test results after SARS-CoV-2 infection have been associated with the presence of viable virus.”

https://www.cdc.gov/mmwr/volumes/71/wr/mm7108a3.htm

So the safe thing would be to assume you are contagious, even without symptoms. In fact, it is not all that unusual to have lingering positive antigen tests, as in the Alaska study we presented in the June 10th post. A quarter of the people with no symptoms still had positive antigen tests after eight days.

Finally, remember that the flip side of antigen tests are the false negatives 1/3 of the time. So when you finally get a negative antigen test, and then a second one, you should be over your infectious period.

Wishing you good health and wellness so that you are able to sing with gusto!

May 31st: Top Ten Covid Myths

Comment: I disagree on two of your points.

-Independent Thinker

#3 - Requiring attendees to be vaccinated and boosted significantly reduces the chances that someone will spread COVID at the event. First because, while there are breakthrough infections among the vaccinated and boosted, they are more likely to be asymptomatic and less likely to spread, and second because they are less likely to be infected than the unvaccinated. Protection declines but does not completely disappear.

Response: I have not seen any evidence supporting your position, and only one study indicating the opposite. We reported earlier (May 20th post) that a computer simulation said there was more benefit to having everyone do a single PCR test ahead of time, rather than requiring proof of vaccination. My understanding is that the aspect of the vaccination protection that partially remains is against hospitalization and death, not so much against getting it or spreading it.

#5 - Masks can protect the wearer but also others nearby. Wearing a mask that is less effective than an N95 can still be helpful in case you are an asymptomatic case and want to avoid infecting others. Some of the virus you breathe out will be stopped by the mask. N-95 is best but other masks are not always worthless.

Response: Yes, even the 25% reduction that I cited is worthwhile.

Thank you for sharing your thoughts; we always like to hear them!


[The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.]

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Avoiding a Superspreading Summer Camp

Reducing the Risk of Short Gatherings

In our May 10th post, we presented how to reduce the risk of gatherings of people who get together for a limited time on a single day. (May 10th blog) Since then, of course, gatherings continue to happen without enough safeguards, and continue spreading the disease. (Pcmag.com 6/16/2022)

This makes sense, as here in New England for example, we are still in a “stealth surge”, with 5-10 times more covid-19 hospitalizations than the lows of last summer. (“Hospitalizations” is a reliable number these days, as opposed to “cases”, of which only a small fraction ever make it into the official counts.) This means 5-10 times more virus circulating in our communities. Here is the chart for New Hampshire - you can go to CovidActNow to check other states:

Reducing the Risk of Long Gatherings

I have heard of several gatherings where people have joined together for two or three weeks, and already covid-19 has invaded their groups.

It does not have to be inevitable for this to happen, but it does involve more elaborate measures.

A long, long time ago (Nov. 29th post), I posted a video explaining how to gather safely for Thanksgiving. It involved a strict quarantine beforehand, and it took a long time with the variant that was active then. Now, with Omicron, things move much quicker—symptoms (and peak infectiousness) typically occur three days after exposure.

Therefore, it might be possible and practical to keep the virus out of the gathering. All the measures of the May 10th post should be followed, particularly having nearly everything take place outside or under canopies. Then in addition, take one of two approaches:

#1 - Quarantine before gathering: for four or five days prior to arrival, everyone would have no close extensive contact with people outside the immediate family. Do confirming covid-19 testing as close to the end of this period as possible. As you know from prior blog posts, this should be a PCR test (false negatives one time out of six) instead of an antigen test (false negatives one time out of three). (Cidrap.umn.edu 6/15/2022) Or, ideally, two PCR tests 24 hours apart.

#2 - Quarantine after gathering: hold the first four days of the gathering without mixing participants in the same room, inside a building. Rooms used successively, such as bathrooms, need a high rate of exhaust air and a few minutes until the next person enters.

If neither of these is possible, then risk can be reduced (but not eliminated) by having everyone do an antigen test and careful symptoms assessment every morning. Yes, every single morning. (This mimics the successful protocols that have been used by various sports leagues.)

Is All This Worth It?

You probably know of many people in your lives who have gotten covid-19 in the last few weeks, during this stealth surge. And probably nearly all of them have recovered after unpleasant symptoms that didn’t require a hospital visit. Yet, there is still the possibility of a serious outcome, and/or various “long covid” effects.

“The omicron variant is much less likely than delta to cause long COVID, according to the first large-scale study published about the long-term risks posed by omicron. But almost 5% of people who catch omicron still experience fatigue, brain fog, headaches, heart problems or other health issues at least a month after getting infected, the study found. While some researchers found the results reassuring, others say the findings are alarming, given that so many people caught omicron and apparently remain at risk even if they're vaccinated.” NPR.org 6/16/2022

Here are two more articles on long covid:

Thenewdaily.com 6/19/2022
Jpost.com 6/13/2022

As a final word, covid-19 has made us all be risk assessment gamblers. There are about 330 million people in the United States. If current covid-19 rates are extrapolated to a full year, 10 million of us will be hospitalized, and 100,000 of us will die of the disease. There is no right answer here—we can live our lives and take our chances, or we can take prudent steps to avoid the risk. I hope that those with each viewpoint can be tolerant of those who take the other approach.

[The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.]

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How Not to Infect Others With Your Covid-19

Infectiousness Lasts and Lasts

With so many people getting covid-19, there is a lot of confusion about how long to isolate, and when it’s safe for others for you to get out into the world.

The public health guidance from the CDC—end isolation after five days—is sending people back while many of them are still contagious. And we know from many previous studies that mask-wearing accounts for only a small risk reduction (for example, about 25% in one multisite study). (Mar. 10th post)

There is a relative flood of recent articles and a few new studies discussing this. Some examples:

An Alaskan study found about 80% of symptomatic patients antigen-positive after five days! (CDC.gov - 2/25/22)

An earlier study from UK said much the same thing, and we talked about that in our Feb. 2nd post.

A good story summarizing the ongoing discussion recently appeared in The Conversation - 5/29/22.

Why This Still Matters

Remember, the days of covid-19 are far from over—U.S. deaths were up by a third over the last week (Washington Post):

And, as we have mentioned, protection from vaccinations and boosters is waning: "The vaccinated made up 42 percent of fatalities in January and February during the highly contagious omicron variant’s surge, compared with 23 percent of the dead in September, the peak of the delta wave ...”

Washingtonpost.com 4/29/22

So, to reduce the spread of the disease, the best practice is to ignore any specific number of days, and wait until you have two negative antigen tests 24 hours apart. Or, if you want to be especially careful, three negative tests. Stay safe out there! (Apr. 7th post)

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