Health Departments & Politics (Oct 21)

I’ve been more than a bit obsessed with Covid-19 since it started. For a while it was almost a full-time gig. These days it’s calmed down to just a few hours a week: reading science papers, and spot-checking a few websites.

Among them are sites for Health Departments in some nearby counties. They vary. All have current numbers, but some break it down by towns; some give a brief description of each case; some have lists of places where infected people visited. Right after the Sturgis rally, Cattaraugus County (4 to the west) even mentioned that two cases were in people just returned from South Dakota. That’s a long motorcycle ride.

The sites are entertaining, in a geeky sort of way. I keep adding more links, and now visit 15 of them. Reading between the lines, they paint a picture of what the pandemic must be like for staff in local Health Departments.

Pre-Covid, their biggest job was inspecting restaurants and other food services. Keep perishables below 45° or above 145°F, don’t put meat above salads in the fridge, control rodents and the like. They also administered WIC, and tried to keep people from catching STDs or growing too obese. Flu shots. Toxic algae blooms. Ticks and Lyme disease. Mosquitoes and West Nile. Opioids. Tobacco. Rabies.

Most of these departments are pretty small. They already had a lot on their plate. This year they’ve been in crisis mode for five months already, and the battle has just started.

Contact tracing and quarantines are an important part of controlling a communicable disease like Covid-19, and that’s mostly what they do now. I’m sure it is not an easy job. You’ve got to ask people where they’ve been and who they were close to. Then persuade them to stay home for a couple weeks. Plenty of people resent authority or think it’s all a hoax. Even the best will be tempted to sneak out for a bit. You’ve got to deal with all that, and probably don’t have much enforcement power.

Normally I avoid talking about politics. As a business owner, I’m significantly less liberal than most folks here in Ithaca. As an Ithacan, I’m more liberal than most people using our software.

Thing is, right now the US probably is headed into a major emergency. A once in a century situation. It’s right in the middle of an election for President, all of the House and 1/3 of Senators. Plus local races.

Both political parties got together in March, and signed the CARES act to support people and organizations affected by the pandemic. Since then, it’s been gridlock and antagonism.

All those local Health Departments will make the difference between a moderately bad Fall/Winter season for Covid-19, and a runaway disaster. To keep everyone safe, they need more staff to trace contacts. More tests. More ability to support folks in quarantine so they don’t wander off and infect others. The states and counties that pay them are facing bigger expenses, and reduced revenues. They can’t print money to make up the difference, and need help.

And of course, many individual people are in the same boat. Life got a lot more complicated and generally worse in March. It’s not turning any corners, anytime soon. It will take extremely competent leadership to manage the next phase of the pandemic, and recover from the economic damage. States and counties can only do so much. Covid-19 is exactly the kind of problem that needs full attention at the Federal level. It’s not happening now.

You might say this country needs to come together, and fight a common enemy: the coronavirus that causes Covid-19. And maybe come together for other stuff also. Life was already headed downhill for many people, even before March 2020.

I miss the days when there were liberal Republicans and conservative Democrats. When politicians compromised and solved problems (at least some of the time). In the end, competence and integrity are what counts.

Dennis Kolva
Programming Director
TurtleSoft.com

Covid-19: Contact Tracing (Oct 12)

Our county had its first death from Covid-19 today. The number of active cases has gradually increased as well. Surprisingly, Cornell is not to blame. They’ve only reported 5 new cases in students and staff during the past week. The rest of the county had 30.

This is not just a local problem. Some parts of Upstate NY have even bigger increases. There currently are 226 active cases in Steuben County (2 to the west of here). 870 people are in quarantine (almost 1% of their population). It’s much worse now than in March/April. So far 60 people have died in Steuben, with 15 in the past week. Their population is similar to here.

New York State is actually doing better than most places in the US. Looking ahead, it makes me very concerned.

It’s possible to divide epidemics and pandemics into three levels of severity.

The best option is full containment. It’s what happened with SARS, MERS and Ebola (twice) in this century. There’s a local outbreak, but medical help rushes in to help the infected. Contact tracers find and quarantine everyone exposed to them. There’s public education, to help folks reduce their risk of infection. Eventually the disease stops spreading. Eventually it disappears.

With Covid-19, some countries have reached containment. China is the biggest example, but most of Eastern Asia is fully contained or close. However, until the disease is completely contained in the rest of the world, they all risk new outbreaks.

The next best option is just plain old containment. It still involves contact tracing and quarantines, to reduce the spread. Still public education to help slow things down. But for whatever reason, the growth rate stays about the same. People keep getting sick, but not at crisis levels. That’s where most of Europe is right now. Ditto for much of the US, especially New England. New York was there all summer, but it’s starting to lose it. Europe is starting to lose it too.

The worst option is out of control pandemic. Contact tracing doesn’t work then, because too many people are infected at once. You can’t keep track of everyone, nor quarantine them all. The disease pretty much runs its course exponentially. Eventually there is herd immunity, but it ain’t pretty getting there.

Influenza did that in 1918 to 1920. Plenty of other diseases did that in prior history. This year it happened for a few weeks in one Chinese province, then in Italy, Spain and New York City. Hospitals are overwhelmed. Almost everything becomes unsafe. Things can get very bad, even when a disease isn’t real deadly. It’s worse when every place is in trouble at the same time.

Steuben may be close to the edge now. They have 15 contact tracers, which means each of them is running daily checks on 18 sick people, plus 40 more who were exposed and in isolation. Things were fine there until Sept 23, then it went off a cliff.

Covid-19 has dominated lives for more than seven months. I think all of us are growing very, very fatigued. The problem is that Spring and Summer 2020 were just Covid 1.0. Best guess is that this pandemic will follow the 1918/9 curve. If so, we’re right at the leading edge of the second and bigger wave.

One big thing we have in 2020 that wasn’t common in 1918 is vaccines, plus the science to develop them rapidly. Vaccines are challenging. The immune system in general is not easy to understand. Luckily, Derek Lowe’s latest write-up on vaccine development sums up current progress. He is a writer for Science magazine, and all his posts about Covid-19 are great. UPDATE: the Chairman of Pfizer also just posted info about their vaccine development.

The short answer is that creating a safe & effective vaccine is a slow process. One probably won’t be ready in time to help with that middle bump (if it happens). But it may reduce the 3rd and 4th ones.

Dennis Kolva
Programming Director
TurtleSoft.com

Covid-19: Droplets (Sep 25)

A couple weeks ago, Cornell University had over 80 active infections, and it was looking pretty dire. Then, the students got scared, and more careful. Last week there were 29 new cases. This week only 5. Someone was hospitalized for a few days last week, but it’s down to zero again. Still no local deaths.

Cornell has already run about 90,000 PCR tests since classes started. Students are tested twice weekly, and staff once. It’s probably not cheap. But, there’s a lot to be said for testing everyone: it nips outbreaks in the bud, and also acts as a reminder that the situation is serious. Having same-day turnaround also helps.

Meanwhile, I’m still doing research for a Coronavirus risk estimator. The consensus now seems to be that most infections happen through the air, so I’ve read a few dozen research publications about droplets and aerosols. The best is a 1934 paper by W. F. Wells. Here are a couple of its charts:

The first shows what happens to droplets that leave a person from talking, coughing or sneezing. Anything smaller than about 140 microns (.14 mm) evaporates, and turns into a floating aerosol. Anything bigger falls to the ground within a few seconds. What that means for Covid-19 is that there are three basic risks:

  1. if you are close enough to someone, you may inhale one of those bigger droplets while it’s still falling. That’s what the 6-foot rule is all about, and the advice to cough into your elbow.
  2. After the big droplets land, you can touch that surface, then transfer virus into your eyes, nose or mouth. It’s the reason for washing hands, and not touching your face.
  3. If you breathe air, you may inhale those small dried-up droplets, which gradually mix into the entire room volume. This is where HVAC comes in. The risk for any space depends on the number of infected people inside and what they are doing, minus air changes and filtration. It’s also why masks are so effective: they block droplets both coming and going.

The second chart from the Wells paper explains why respiratory diseases are more common in winter. People are indoors more, which is half the problem. Even worse, the air is heated and dry, so more droplets evaporate, float around, and end up in noses and lungs.

When working with droplets and aerosols, it’s easiest to do everything in microns (symbol µm, aka micrometers). A micron is one thousandth of a millimeter. It’s about the size of the biggest tobacco smoke particles, a medium-sized bacteria, or the smallest pollen grains. PM2.5 pollution is 2.5 microns and smaller (the most dangerous size because it gets into your lungs easily). N95 masks filter 95% at 1/3 micron size. They hit 99% for both smaller and larger particles. 3M says that’s because the bigger particles are heavy, and ram into a fiber. Smaller ones are extremely light, so the fibers suck them in by electrostatic attraction. 1/3 micron is the sour spot in between. A coronavirus is about 1/10 of a micron.

A few researchers have measured the amount of Coronavirus in mucus and saliva: results range from 12 million to 36 billion virions per cc. It’s simple math to translate that to the amount of virus in droplets of different sizes. As it turns out, a one-micron exhaled particle only has a 2% chance of containing a virus, even at the maximum rate. The bigger droplets that dry up and then float are worse. The maximum size that evaporates in humid air (97 microns) will contain somewhere between 3 and 17,000 virions. The maximum in dry air (172 microns) has 16 to 96,000.

As those droplets lose water, they shrink down to roughly 10 microns diameter (about average pollen size). They become a tiny glob of mucus proteins and passengers, light enough to float for hours, easy to inhale. By the math, those are probably the most dangerous.

Dennis Kolva
Programming Director
TurtleSoft.com

Covid-19 in New York #4 (Sept 5)

There are two colleges here in Ithaca. Both planned to have classes on campus. Ithaca College (the smaller one) changed their mind a few weeks ago. They will be online-only for the Fall semester. Cornell went ahead with their reopening plans, and classes started on Wednesday. The Vet School laboratories are testing all undergraduates twice a week, which sounds great in theory.

Three weeks ago, there were 7 active cases of Covid-19 in the county. A week ago there were 19. Yesterday, there were 70. Most cases happened because students had parties without masks or social distancing. Who could possibly have suspected that might happen? /s

Maybe everyone will get scared, and change their behavior. More likely, there will be enough cases to trigger an automatic shut-down, per NYS regulations. We’ll see.

Meanwhile in the rest of the US, the State Rt tracker shows wavy curves for every single state. Today the majority of states are positive. Sometimes the majority are negative. It seems to vary on a few-week cycle. Back in April I compared state responses to skidding on icy roads. Because of the feedback delay, it’s easy to lose control and end up in a ditch.

Luckily, that isn’t happening with Covid-19. Most states seem to be converging on a Rt value close to 1. That’s probably the ideal growth rate, as long as the case count is low: the best balance between health and economic activity. I guess it also applies to ice and snow: most drivers in the North eventually figure out how to slow down the feedback cycle and stay on the road.

Globally, infections are also at a steady state, with about a million new infections every 4 days. Much of Europe is starting to see early stages of exponential growth, again. It’s going to be a long haul.

I’m still working on an Excel spreadsheet that calculates Covid-19 risk. There are many studies with useful info, but nothing that translates directly into hourly risk. It will require some assumptions and guesswork to get it calculating accurately.

Covid-19 risk is mostly a matter of HVAC. The amount of virus you inhale is equal to the number of people nearby, times the % that are infected, then divided by the volume of air and the number of air changes per hour.

At least a dozen case studies have been published: cruise ships, a Seattle choir practice, a Maine wedding, church events. I have been using Google maps and other sources to estimate building sizes. Air changes is totally a guess.

The biggest uncertainty was expressed best by Dr. Gregory House: “everybody lies”. Folks don’t want to miss work, or they really need a pack of cigs, so they get into public space even though they are shedding virus into the air. Odds are good that they don’t wear a mask. They avoid testing and don’t get into the official data, so the math is more difficult. Everyone’s lives are more difficult.

Dennis Kolva
Programming Director
TurtleSoft.com

Roofing, Risk & Covid (Aug 18)

I dropped out of Cornell in 1971, bought some land, and started doing odd jobs. One of the first was at minimum wage, for an old geezer who hired me to put roll roofing on his gambrel barn. He sat in a wheelchair at ground level and talked me through the whole project, step by step. It was all done on old wooden ladders, with a few patched rungs. I was terrified the entire time. Thinking back, there was good reason to feel that way.

Right now I’m re-roofing my own house. I bought some good fall protection for the job, but then decided even that wasn’t enough. So, now there is a comfy scaffolding platform at the eaves, with safety rails. It’s almost like working at ground level.

These days, the risk that scares me most is not falling and dying. Something less could easily be worse: serious injuries, massive hospital debt, chronic pain, permanent loss of mobility. It’s also a matter of comfort. As a builder/remodeler I often worked on roofs with just a safety rope around my waist. Back then I woke up all the time from falling dreams. Now that I do construction more safely, they are very rare. It’s nice to sleep well at night. Less working at odd angles = less back pain. Thank you OSHA.

BTW someone mentioned the unsafe angle of the orange ladder. It’s a support slide for 17 foot roof panels, raised with a rope winch via a pulley at the ridge. Humans use the 3 small ladders inside the frame.

The same risk calculation plays out for Covid-19. What scares me the most is a long hospitalization, then chronic lung damage and piles of debt. Even a mild case still means two weeks of quarantine, boredom and worry. Masks and social distancing are inconvenient, but much less so than what they prevent.

Many colleges that reopened are seeing outbreaks. Cornell and other local schools still plan to open on-site, so I am very worried about the next few months. It inspired me to start building a Covid risk estimator, using Microsoft Excel. It will help for personal decisions.

The process is similar to construction estimating: break things down into smaller pieces, calculate each of those, add them up. For construction, the components are scaffold setup, square feet of metal roofing, skilled labor. For Covid-19, it’s risky environments, and time spent in each. Add up the construction costs and you get a dollar amount. Add up life in 2020 and it’s an estimate of inhaled virus particles, and odds of getting sick.

Turtlesoft got its construction estimating data from our own projects. Covid-19 will be trickier. There’s a fair amount of useful data out there, but it does not translate so easily into virus per hour.

A basic problem for any estimating system is accuracy. Our construction unit costs were calibrated by matching them to actual costs for our remodeling projects. Then we refined them with feedback from users. For Covid-19, I’ll run it on a few case studies like the choir practice in Seattle, and tweak the values so it hits on the nose for those. County case counts and cell phone location data from the Social Distancing Scorecard will also help, especially from back when nobody wore masks.

This is not a rush project, but it ought to come together over the next couple weeks.

Dennis Kolva
Programming Director
TurtleSoft.com

Covid-19 in New York #3 (July 26)

Upstate New York was doing great for a while. From mid-June until July 9, there were only 1 or 2 active cases of Covid-19 in our county. Most surrounding counties were equally low.

I think people started to think the problem was all over. They visited out of state, and had Independence Day parties without masks or social distancing. As a result, Covid-19 surged back. This past week, the number of active cases in the county has ranged from 32 to 39. It’s almost as many as during the peak in late March. Surrounding counties also have spikes. Oops.

At the peak in March, there were 18 people hospitalized with Covid-19. That dropped to zero, most days in May and June. This week saw a maximum of 4, but it quickly went back to zero. There is much more testing now, so March and April probably had hundreds of hidden cases.

Fortunately, still no deaths in Ithaca and environs. Some nearby counties have experienced 10 to 60 fatalities, especially where the disease hit nursing homes.

On a national scale, the State Rt tracker is starting to show interesting wiggly curves for most states. Growth rates go up, until there are enough cases to make people panic and become more careful. Then growth rates decline, until people breathe a sigh of relief and go back to their old ways. Rinse, repeat.

Globally, cases are exponential again. The number of new daily cases is increasing with the same curve as cumulative cases. That’s how exponentials work.

This disease is not fading away just because the weather is hot. It probably will get worse in the Fall. Many vaccines are under development, but getting a well-tested one that’s both safe and effective is still many months off. So the big question is, how to have some semblance of a normal life as long as Covid-19 is still around?

The IHME Covid Projections site makes predictions for most countries and all US states. It now estimates deaths and infections up until November 1, calculated with and without universal mask adoption. The difference is huge, especially in places that are currently hit hard. Overall I think masks are probably the cheapest and easiest way to reduce transmission, and still carry on economic activity that is as close to normal as possible. There are other options too, but none better than blocking those pesky snot droplets right at the source.

Personally, I wear an N95 mask a lot. Definitely indoors in places with other people. Also outdoors when within 6 feet of anyone who is well-masked. I give 20 feet to anyone bare-faced, or wearing a chin-warmer. I saved seven N95s from a box left over from lead paint removal, and labeled one for each day of the week. They all have an exhaust port, but I put tape over it as a courtesy to other people. After 4 months of use the straps are starting to get ragged, but they still work. Hopefully they’ll last until replacements are back in stock.

Many people around here wear masks, and/or give other people plenty of distance. Unfortunately, there are also plenty of Covidiots who don’t give a crap. I asked one non-masked jogger to give me 6 feet as he charged at me on the sidewalk, and he just ran up close and laughed ha ha right in my face. So now I listen for footsteps and scramble out of the way. It’s safer to walk in traffic, rather than close to idiots/narcissists/sociopaths/whatever.

It’s really too bad that the US recommended against face masks for so long. Too bad that leaders didn’t set an example, for so long. The Feds and most states still haven’t figured out effective messaging, to get people to wear them (and wear them properly). I would suggest pushing a conspiracy theory that Bill Gates has cameras everywhere, and masks are the only way to escape surveillance. Its software uses nose and mouth, so make sure both are covered well.

The only good news is that the US approach is going to be great for epidemiologists. There are 50 different states doing different things, and getting different results. Thousands of cities and counties with assorted rules, and varying compliance rates. It’s going to be incredibly useful data.

Meanwhile, I am still stripping old asphalt and adding new metal roofing on my house. The project just hit 25% completion. I’ve never assembled scaffolding before, nor worked with such long sheets. It’s quite a challenge to remove 3.5 tons of decades-old shingle without creating a mess.

So far I have made almost every possible mistake. I guess that is pretty much how I’ve always learned construction. Or programming. Or anything else in life.

Maybe that’s what the USA also needs to do: make every possible mistake. Then the next pandemic will be easier.

Dennis Kolva
Programming Director
TurtleSoft.com

Covid-19: USA and the World (July 8)

I spent a couple days with Excel, futzing with John Hopkins data for Covid-19. The result is charts showing per-capita infections for the 90 most populous countries (confirmed cases per 100K people). They divide up fairly neatly into 5 groups.

First of all are countries that contained the virus quickly. Except for one city in China, their hospitals were not overwhelmed. Life is close to normal for them, now.

This group is about 27% of the global population, mostly in East Asia. That region had a scary experience with the SARS epidemic, so they knew just what to do for the Covid-19 outbreak: quarantines, contact tracing, testing. Local lockdowns when those weren’t enough. Almost everyone wore masks in public, even before the pandemic. They do help.

Next are countries with a low rate that is still growing. These are about 20% of global population. Almost all are Third World or close. That means the low numbers could be from lack of testing, rather than lack of disease. Australia (thicker line) is the outlier. They contained the outbreak for several months, but Covid-19 has recently started to increase again. It’s mid-winter in the Southern Hemisphere, which may be the culprit. That will also be the theme for other countries, later.

For the next three graphs, the vertical scale is compressed by 5x compared to the previous two.

The “getting serious” middle group has exponential growth, with infection rates that are just starting to be dangerous. Columbia (thick blue line) and Mexico (thick red line) are the worst. India (thick green line) is lowest per capita, but it may be under-reported. These countries make up about 36% of global population.

The fourth group had scary rates of infection in March to April, but they are mostly contained for now. Covid-19 snuck up on them, but all these countries responded well. All are First World countries, with 5% of global population.

Then there are the 15 countries already facing a serious impact from Covid-19, with infection counts that are still increasing. You might say these are the basket cases.

Worst of all is Chile (black line), which currently has 1,527 confirmed infections per 100,000 people. That’s over 1.5% of their population. It made the graph too tall for WordPress to handle, so I had to cut it off at the top. Peru (green) is #2 with .91% infected, Bolivia is #11, and South Africa (purple) is #12 and growing fast. Argentina is also exponential, but just below the cutoff I used. All five of those countries are in their winter seasons. That probably is a very bad omen for the Northern Hemisphere, looking ahead to Fall.

The next most bad-growing-worse countries got that way because of politics. USA (#3 red), Brazil (#4 yellow), Saudi Arabia (#6 orange) and Russia (#7 gray) all have autocratic rulers who started out denying that Covid-19 would be a problem. When proved wrong, they still didn’t do much to help fix things. Sweden (#5 light blue) tried a bold experiment, and didn’t shut down. They ended up with more infections, and an economy no better off than the rest of Europe.

All this stuff is just numbers, but it represents many people’s lives. Looking at that steep red line for the US makes me very angry, and very sad. How did we fuck up so badly? But I’d better stop now.

Dennis Kolva
Programming Director
TurtleSoft.com

Covid-19: Reopening (Jun 29)

New York State has been reopening gradually, with a minimum of 2 weeks between each phase. Ithaca entered Phase 4 on Friday, along with most of Upstate NY. Dine-in was allowed in Phase 3, but many restaurants are still takeout-only, or completely closed. All gyms are still closed, as are most bars. Large public events are still forbidden, and masks are required for all indoor public spaces. Outdoors, mask use seems to range from 0% to 70%, depending on location and time. I think it’s declining.

The Rt tracker site currently shows 33 states with increasing infection rates, and only 17 decreasing. New York had a low number through most of April and May, but it gradually inched up. Today it is exactly 1.0. If it stays there, the number of daily infections will remain the same indefinitely.

Since the current number reflects conditions from a couple weeks ago, it is very possible that NYS has reopened too quickly. The ideal balance between safety and economy probably was back at Stage 2 or 3. We will find out about that in a few weeks.

At least Covid-19 is close to contained around here. The county health department is doing almost 1500 tests a week, with only two of them positive on average. Nobody has been hospitalized here since May 29. Nobody local has died yet. Conditions are worse in the bigger cities within a few hours drive, but still tolerable. Even New York City is inching back from the brink.

Sadly, some other states are starting to become very dire. Most of the US reopened too quickly. Governors are starting to crack down, but they will soon find out what happens with exponential growth and a time lag. For example, right now the estimated Rt for Florida is 1.4. That means cases will almost triple before any impact shows, from remedies started today. Florida already has 9500 new daily cases, so it probably will get worse than New York City was in April, and soon.

It’s like watching a slow, enormous train wreck. Too bad it’s not just a train, but the whole frigging country.

Meanwhile, the big question locally is what happens after Cornell reopens this Fall. They just issued a 97 page report about it, but it leaves many details dangling. I think a lot of their plans ignore what students in their late teens and early 20s are like. The local economy is very dependent on the two colleges, so it’s going to be a very interesting ride.

I am pushing 70, so it makes sense to continue social distancing and mask-wearing, even though risks have declined. Most likely that will continue for at least another year. Masks suck, especially in hot weather, but they are a lot more comfortable than a respirator.

To cut down on exposure, the Turtlesoft office is currently open just one day a week. We probably will keep that schedule for most of the summer. Maybe longer. User support is still available by email, and usually by phone.

I spent the stimulus money on scaffolding. So I’m stripping 3 layers of ancient asphalt roofing off my house, and installing metal. It’s also a chance to finish up the exterior painting a bit more safely, and hang new gutters. After that, we’ll see. If QT seems plausible, at some point Goldenseal Pro will consume much more time again.

Dennis Kolva
Programming Director
TurtleSoft.com

Covid-19: Herd Immunity (Jun 16)

According to OpenTable, restaurant reservations in the US increased to 33% of normal, as of yesterday. It varies a lot between states: Rhode Island is close to 100%, while New York, Hawaii and DC are still under 10%. Those numbers are probably a decent indicator for general levels of reopening. The sharp dip yesterday was because it compares to Father’s Day 2019.

The Rt tracker website now shows 19 states with growth multipliers above 1. Arizona leads the pack, while most states in the Northeast are near the bottom. New York was #1 for new cases during most of April and May, but it fell to #8. The action has shifted south and west. Specific numbers vary with each update, but the trend has been consistent.

JUNE 19 UPDATE: the Rt tracker revised their calculation method today. They now show 26 states with growth rates greater than 1 (daily infections increasing). Several states are starting to look very scary.

Since economies are still ramping up, the best guess is that the growth rate will continue to increase. At some point, states with a growth rate much above 1 will run into trouble. Presumably they will then take action to reduce infections.

That means the Rt rate will probably hang out close to 1, pretty much indefinitely. For every infection that ends (via recovery or death), a new one will take its place (on average). Of course there will be large variations in different places.

In a previous post, I talked about containment. It can happen globally if every country reduces infections to zero, until the virus disappears. That’s what happened with SARS and MERS, the two previous coronavirus epidemics. Sadly, it seems very unlikely that containment for this one will ever happen in the US, nor globally. Covid-19 is just too well established. A few island nations have reached zero cases, but that’s still not great. They constantly will need to quarantine all visitors, or risk fresh outbreaks.

For a non-contained disease, the only other end game is herd immunity, which occurs when a critical mass of people are immune. If non-immune people are rare enough, then the disease gradually stops spreading. The amount of immunity needed depends on a lot of factors, but it’s usually between 60% and 90% of the population.

With herd immunity, the disease may eventually die out completely. It may stick around as a minor problem. Or it may return in surges, as each previous wave’s immunity fades away.

There isn’t anywhere with herd-level immunity to Covid-19 right now. New York City is probably the closest, with about 20% showing positive antibody tests. Elsewhere in the US, it’s rarely over 5%.

Doing some very quick math, if 3 months of infections made 5% immune, then it will take 45 months to hit 75%. The curve will be flat, but very wide.

Of course, vaccines are a great way to increase herd immunity very quickly, without all the sickness and death. In the US, roughly 60% of children and 45% of adults got a flu shot in 2018/9. For Covid-19, a recent survey showed 49% who plan to get a Covid-19 vaccination. 20% are unwilling, and 31% not sure.

That probably isn’t enough to attain herd immunity in one swell foop, but it’s close. After a vaccine is available and after half the anti-vaxxers get infected, the US will hit herd levels of protection.

Dennis Kolva
Programming Director
TurtleSoft.com

Exponential Growth #4: Containment (May 23)

In past posts I’ve talked about exponential growth when it’s fast and scary, and when it’s close to flat. But there’s also negative growth, with a multiplier of less than 1.

Right now, the Rt Tracker website shows all but four states with Rt like that, from Arkansas (.99) all the way down to Alaska (.63). If they can stay below 1 for long enough, Covid-19 eventually will reach containment.

Here is a chart of exponential growth rates less than one. It shows how the number of new cases of Covid-19 will decrease for each Rt multiplier. The lower the number, the faster the approach to zero.

Right now there are four states with Rt values under .82: Alaska, Hawaii, Vermont, and Montana. All have relatively small, isolated populations. They never had many cases to begin with, and are close to zero now. With local containment achieved, their biggest worry is new cases that come in from elsewhere.

The next lowest state is Connecticut, with an .83 multiplier. They had over 2000 new infections at the daily peak, but the average is about 600 now. At current rate of decline, it will take roughly 50 days to drop by a factor of 10 (to 60 new cases per day). Another 50 days gets it to 6 new cases. The theoretical curve never reaches zero, but with actual humans it’s possible to get there eventually.

Other states with higher Rt values will decline more slowly. Some will be very, very slow.

Exponential curves and Rt charts are pretty, but they are just theory. Actual containment depends on what people do each day: how much they stay home, how much they congregate, whether they wear masks. Just as important is the work of state and local health departments. They have battled all sorts of diseases over the past century, and this is just another for them.

To contain a disease, health departments do whatever it takes to reduce the infection growth rate to something less than one, then keep it that way.

Vaccines are the best way to contain a disease. Many folks are working on them for Covid-19. Next best is contact-tracing and quarantines. If those aren’t enough, then the only recourse left is massive social distancing. Economically, it’s an extremely painful option, but less bad than having many people suddenly sick and dying at the same time.

The ideal way to conquer a dread disease is to get global containment: already accomplished for smallpox, and almost completed for polio. Total containment is very hard work. Health workers must go into poor and war-torn regions and vaccinate enough people to reach “herd immunity”. It also requires plenty of contact-tracking and isolation until the last cases are completely gone. One sad consequence of Covid-19 is that it sets back the efforts to eradicate polio.

The Rt tracker site seems like a very useful tool. However, Rt is based on actual test results. It lags by at least a couple weeks, because it takes time for infections to develop, tests to be processed, and data to be entered into the pipeline. Today’s numbers reflect conditions from when state just started to reopen in early May. The social distance scorecard is probably the best way to predict the future, but it’s a very crude guide based on smart phone locations. It doesn’t adjust for mask use, indoor vs outdoor contact, or sanitation measures. Lately it rates most of the US at D or F, but I think reality is a grade or so better.

As social distancing relaxes, it will be interesting to see how much it affects the numbers. States will probably jump around with changes in weather, policies and people’s behavior. The risk is always there for an outbreak, with a sudden return to scary exponential growth. A single ‘super-spreader’ event can push any state to well above 1.

SARS and MERS were caught soon enough to be 100% contained. Covid-19 became too global, and it’s unlikely to ever reach full containment. Even with a vaccine. However, it can become like measles, influenza and other diseases that are controlled enough to not cause big catastrophes.

Dennis Kolva
Programming Director
TurtleSoft.com