Why aren't we all infected yet?

As much as I hate to use math tell me why we all haven't been exposed to someone that has the virus by now. Using the penny doubled every day model,

https://www.al6400.com/blog/a-penny-doubled-everyday/

if just one infected person came into this country in early December by today the odds are we'd all have at least one encounter by now.

Is my math wrong? One of you smart guys can set me straight. Does encounter not equate to getting the disease? If so, is there a more than likely profile of who might get it besides the old and the young? Thanks.

 

The major problem with the penny doubled every day is that in some areas, the same person will come in contact with many people who might have the virus and in other areas, they only come in contact with people who do not have the virus. It tends to occur in pockets because one person coming into a crowded area infects many.

 

I've been confused about this too. I'd been told by many smart people that the growth in infections was going to be exponential. I assumed that meant a doubling of infections each day. But mathematically, that requires a time component, which no one actually uses, so the term was effectively meaningless. There is a massive difference in the number of infections doubling every day and doubling every three days.

 

Social distancing is working and (up until now) the USA has gotten lucky.

Easter is 22 Days Away.

Let's revisit this on Easter and see where we are then.

At that point we should know if it was "unjustified panic" or not.

Time will tell.

 

I know of no one that has been infected.

 

For the same reason that compound interest doesn't make you a billionaire in a month.

If the number of infections increases by 1% a day it would still be exponential growth.

 

That makes the term effectively meaningless.

 

Lots of people can already have the disease, but you'll never know it because
a) their symptoms are mild
b) they don't get tested

The problem are for those who need ICU beds, ventilators and become critically ill, there are limited supplies for the number of people that can be treated in intensive care and therefore they try to keep the virus from spreading fast. High infection rate means lots of beds/equipment needed at the same time, slower infection rate means less pressure on the health system and more lives can be saved.

There is absolutely no "unjustified panic" this is clear from what is unfolding in Italy. Concern & actions taken thus far is 100% justified. There are clear strategies in place on how to deal with Coronavirus that governments are following. If there is confusion it is the media not doing their job and people not adhering to social distancing

 

I social distance regularly anyway so this is nothing new to me. I love my sad existence. It has proven the way to go for me.

 

I was thinking about that today. The only person I know of claiming to have/had COVID-19 is the daughter of a person we’ve done business with. The daughter in question is in Europe. Does anyone here know someone with C-19?

 

Earlier today, I commented, "No one is immune," because that is what we keep hearing, and we should operate under that assumption.

However, I just tripped across this article which suggests that a large portion of the population probably does have a natural immunity, otherwise 90% of the people in the world would have had coronavirus in the first 90 days, given exponential growth and no immunity.

Certainly the advice for social distancing and staying home as much as possible should continue to be practiced by everyone until we see where it levels off, but there is reason to be optimistic.

https://www.jpost.com/HEALTH-SCIENCE/Israeli-nobel-laureate-Coronavirus-spread-is-slowing-621145

 

Delete duplicate

 

They reported 62 cases here today. Before I left work yesterday, there were 16 or 18 (I don't remember the exact number yesterday, but it was in the teens). I'm expecting a huge rise now that we have not only state lab testing, but also a new drive-thru testing place.

I mostly go to work and come home, so my biggest contact-risk would be having to make a crazy-abnormal number of trips to the grocery trying to find a dozen eggs on the shelf.

 

yeah, millions aren't interacting at Walmart, the grocery store, carry out establishments, factories, hospitals, ........

 

New rule in the city issued today. Groceries and other businesses which are allowed to be open must enforce 6ft distance between customers. lol Good luck with that, when most of the customers won't know that new rule.

The shelves are still empty here though anyway, so I gave up trying to get eggs and a bag of rice. Sigh.




They also want employers to take employees' temperature.

 

Coming into contact with someone doesn't necessarily mean you get the virus from them. Its only if they cough or sneeze, and some of that gets into your nose or mouth. Or you touch their hand, or a surface they touched recently, and then you touch the inside of your nose, mouth, or touch or eye. Trump was around someone with Covid a while back, and his test recently came bad negative for the virus.

Another problem is that we are severely under-counting the number of people infected. Because it takes up to three weeks to see any symptoms, some people never get symptoms at all, others get what seems like mild cold or flu, some people just don't want to report they have covid, and the lack of testing kits we have in the US, we are under-counting by a factor of maybe 5-10. So everyone could have this thing, but the official numbers won't say that.

Also, China took some extreme measures to quarantine this virus and greatly slowed its growth. The US did start seeing some cases, but until mid-march it was less than 100 and most of these were people who went to China or was around someone who did. It wasn't until the beginning of march when those few cases started increasing exponentially. So we have only had three weeks for this virus to spread, but it has gone from less than 100 to 25,000 as of March 21.

And that is the thing with exponential growth. Today there are 26,000 infected, last week it was 3,000, the week before it was 400, and the week before that it was 70. We are a week away from 140,000 infected in the US, and another week from 520,000 infected. And that assumes that the rate of growth slows down due to quarantine measures. If that rate slows like it has in Italy and that slowdown continues, the number of cases should peak at 1.4 million in a month from today.

 

I wish a grocery store would offer a basic sustainment box, for example: gallon of milk (any kind), 2 sticks of butter, loaf of bread (any kind), Quaker oats or other brand, box Cheerios, dozen eggs, pound of bacon, 2 pounds of hamburger with bag of buns, jar peanut butter, jar of jam, small bag of potatoes, bag of rice, bag of beans, 16 oz. cooking oil (any kind), 2 rolls of TP (any kind), roll of paper towels (any kind), bottle of 70% alcohol or hand sanitizer (as available) no substitutions, except add on baby formula, Gerbers, and diapers as optional, dishwasher and wash detergent optional but no choices.

You call, pay by credit card, drive to store, show ID, they throw the cold milk into the standardized box which is easy for them to have ready, and they put it in your vehicle. You drive away having kept max possible social distance instead of pushing a shopping cart in the store.

You got calories, carbs, proteins, and fats and are set for a while with far less chance of getting the Wuhan virus. Safety replaces individual choice and you get some food. What you don't want in the box give to neighbors.

Stores could maybe offer some kind of standardized treat bag for kids.

We're set but the full parking lots at Walmart ain't a good omen.

 

Where are the vegetables? lol

I've thought that's what the government should do for food stamp recipients...give actual food boxes with a balanced diet and some TP and cleaners, instead of cash cards.

That's too restrictive on choice though when there is no actual food shortage and people have money (or food stamps) to buy what they prefer.

We are spoiled and lucky.

 

It is exponential, at least in the initial growing phase, just like compound interest growth. The rate constant with which it grows is similar to the interest rate in your bank account. If that interest rate is 7% annually, your investment doubles every 10 years. If the "interest rate of the virus is 7% per half a week, it doubles every half week, which is the current rate of growth. In kinetics, this factor that determines the speed of the process is called the rate constant.

Second, as with ANY exponential process, growth eventually ceases to be exponential. For the virus, this happens when it runs out of new hosts (either it has killed many, or they have become immune, or the virus has mutated to adapt to the new host, making it less lethal). The number of infected people will then go to a steady state (level off, like we see in China right now), or, hopefully, decline back to zero.

The number that determines the growth rate is called R0, i.e. how many people a sick person infects, on average. For the normal flu, that value is 1.3 (it has to be over 1 for the infection to be sustainable). For covid, it is more likely 2-3, much more infective. That's where social distancing comes into play, it reduces R0 (hopefully bringing it down below 1), and, thus the growth rate.

The funny thing is, it is easy for us to see how rapid exponential growth eventually leads to self destruction of the virus. It is very difficult for us to see that rapid economic growth (which is also exponential), will eventually have to stop, or it will do the same thing to humanity.

 

Yes but my issue is that getting information from news, there are epidemiologists and doctors who are using the term "exponential growth" with no qualifier as to what they are referring to over time. As you said, "interest rate of the virus is 7% per half a week, it doubles every half week, which is the current rate of growth." However I'm only being told the interest rate, not the factor of time involved. 7% interest per half a week is quite different than 7% interest per year, or decade.

 

If no one is immune, my non medical doctor mind thinks that means that everyone who is exposed to the disease will get it. But that didn't happen on the Diamond Princess where everyone was tested, everyone was exposed, but not everyone got the disease. So clearly some people have some immunity.

 

The function representing growth is RO^x, where x is determined by the time constant. If one can be innoculated with virus and shedding a high viral load is 2-3 days, than the time constant is in the range of a few day. The exponent x will increase by one every few days.

 

And wouldn't that be good news, relatively speaking? I heard that about 30 million people get the flu every season, and about 30,000 - 50,000 die. So extrapolating numbers, if 1.4 million get coronavirus, and there is a 1% mortality rate, that would mean 14,000 die. Even at a 2% rate, it would be 28,000 - or a "low average" when compared to the seasonal flu.

That would mean, should this peak at 1.4 million people, it would have been less lethal than our ordinary, every-year flu.

 

I'm not being told x. That's my issue.

 

Can't say, but it has got something to do with the numbers of people that have actually been tested and the numbers who went into isolation in time. But Over the course of the past week the numbers of cases reported inside New York City has increased by roughly a thousand people per day. Last week it was just over a thousand. Now it is a little over eight thousand reported cases.