Coronavirus - worldwide spread and control

[alex3619]

Maybe once above a certain level it is very hard to slow things down in a short period.

I just saw an interview on CNN with Anthony Fauci who basically said as much. Its easy to contact trace small numbers, its impossible once large numbers are infected, and mitigation is the only strategy at that point. Once numbers are down you then need to do mass testing and lock down the remaining infected. You still need to do mass testing in the meantime though, or you don't know who has it and whether the infection rate is going up, is level, or going down. Not having tests, not having protective equipment, and not imposing social isolation, all contribute to the rising infection rate.

PS

 

[alex3619]

I imagine that kissing an COVID infected friend the sofa all evening, would transfer a higher initial viral load to an uninfected person, than might be received if you were unlucky enough to pick up the virus walking past the same infected person outside.

Again, Fauci just discussed this. The higher the initial load, the bigger the risk as the virus will replicate much faster, giving the immune system less time to respond.

 

[alex3619]

And as we have seen with country graphs of the number of infected people, the early increases seem slow, compared to what happens once the numbers increase.

This is classic exponential growth, and is contrary to human intuition. Those familiar with exponential growth, often scientists, are not surprised.

 

[alex3619]

They may not PREVENT the wearer getting an infection, but if they manage to reduce the initial dose of virus, then they buy the mask wearer more time.

I see two main values, unless these are high grade medical masks which are purpose designed. First, you cannot touch your face under the mask, just don't keep adjusting the mask. Second, if you are infected they will stop small droplets from coughing etc. getting out. Viral particles easily pass through most masks, small droplets are much less likely to pass through.

Decreasing viral load is not unimportant though, the size of the initial infection might have a major impact on disease progression.

 

[Sasha]

I agree. This makes no particular sense. I think it was intended to give an idea of risk. But it is hard to see how it can be based on evidence. I have a suspicion it was largely intended to reassure people that getting close to a passer by need not induce panic. That advice had clearly been turned around - we are not supposed to get within 2 metres for however short a time now.

Thanks very much. So is it the case that a single particle of virus is all that's needed to cause an infection?

I'm wondering if any amount of handwashing etc. is enough to protect against that if we've been outside, or whether a single breath from someone getting too close is enough.

I don't want to be paranoid but I don't want to die of ignorance, either! I've been out extremely early in the morning the last few days but even so, there are still people on the street and several don't seem to understand what two metres is. Especially joggers!

 

[Simbindi]

Just tracking the number of deaths UK has had due to Coronavirus, compared to Italy.

I found this data of deaths in Italy vs UK at different times.

Up until 4 days ago, the UK and Italy were very much on a similar track. However over the last few days, that seems to have diverged quite a lot. The deaths were around 40ish for a few days, then 80, and then today around 30.

View attachment 10318

On cumulative deaths, Italy 7th March is similar to U.K. 21st March. But 4 days later, on 11th March, Italy had 827 deaths. 4 days later for the UK, we have ~ 450 I think. Nearly half.

Does this represent a trend? And if so, why would that be? If anything, people in the UK have been out and about, socialising as much as people in Italy I would’ve thought, lots of big events happened, also generally there wasn’t much restriction or social distancing 10-14 days ago. Up until 4 days ago the trend was similar. So what can explain this difference? Is it just too early to tell?

Obviously I am just guessing, but in the UK the population age demographics vary according to geographical location. There is a higher percentage of elderly (at higher risk of dying) in rural areas, whereas London (seen at the epicentre at the moment) has a relatively younger, less at risk of severe illness, population. So it may be that in the UK more of the most vulnerable population were keeping more social distance (having fewer number of contacts per day) in their everyday lives even before the social distancing restrictions were introduced.

We may see deaths rates varying in the future by geographical location if rural hospitals become overwhelmed (so it is good that they have now closed hotels, holiday and caravan sites in these areas to prevent a sudden large influx of people to these areas).

 

[Jonathan Edwards]

I think Fauci gets the Italy dynamics wrong. If it was due to masses of Chinese tourists there would have been hotspots in Rome, Venice, Pisa, Florence as well as the relatively less popular Milan. I see the problem as simply the expansion of a single case-based outbreak (maybe a coach load but why was that never picked up?) at a time when people were not even thinking of the diagnosis.

 

[Adrian]

Thanks very much. So is it the case that a single particle of virus is all that's needed to cause an infection?

I'm wondering if any amount of handwashing etc. is enough to protect against that if we've been outside, or whether a single breath from someone getting too close is enough.

I don't want to be paranoid but I don't want to die of ignorance, either! I've been out extremely early in the morning the last few days but even so, there are still people on the street and several don't seem to understand what two metres is. Especially joggers!

Isn't some of it about risk and the likelihood of getting it in a particular way. For example, even if handwashing doesn't completely remove the risk it would significantly reduce it. Equally I think the 2m and 15 mins is about there being a high risk with risk being reduced as time is shorter.

 

[Jonathan Edwards]

I'm wondering if any amount of handwashing etc. is enough to protect against that if we've been outside, or whether a single breath from someone getting too close is enough.

One virus particle has to be enough, although it may be that nearly all serious Covid19 depends on a larger dose, to get the process started before immunity kicks in.

It must all be a matter of statistics and the fact that spouses quite often do not get infected must mean that the vast majority of the time virus particles from someone breathing near you do not reach you nose or mouth and latch. I see it as a bit like birch tree seeds. One seed will grow a tree but even close to a birch tree shedding tens of millions of seeds in a season nothing may grow at any particular spot.

I think the hand washing is important because your hands have about a hundred times the surface area of your mouth and nose and we keep rubbing our mouth and nose with our hands. The chances of getting virus on your hands is much greater than getting it on your lips. Hands also touch all the surfaces that may be a thousand times larger and finely coated with virus.

If just walking past someone was a significant risk then the R number for transmission would be about 100. It seems to be about 2 so the chance must be small (and far less than 1/50 because it is not that simple! R relates to everyone infected over a period of many hours or some days.).

 

[Sasha]

One virus particle has to be enough, although it may be that nearly all serious Covid19 depends on a larger dose, to get the process started before immunity kicks in.

Thanks very much. Yikes, I'm staying in, then...

Given that we're all starting from no immunity, how long would it be before the immune system can mount a response? Could it be fast enough to eradicate the virus within hours, say? I remember reading about how much contact any molecule in the blood has with the rest of the body and being pretty amazed, so I'm wondering whether even a few antibodies could find their targets very quickly.

 

[Jonathan Edwards]

Given that we're all starting from no immunity, how long would it be before the immune system can mount a response?

How long have you got? It would be hard to give a full answer to this in a one hour lecture!
In general we deal with pathogens the first time with innate responses and antibodies are there to stop you getting the infection a second time. First time round immunity also draws on recruiting cytotoxic T cells over a few days. We tend to rely on having a good repertoire of these built during childhood whether or not we have ever seen the antigen but the relevant ones need growing up from memory stores.

 

[Woolie]

We've just had our first day of complete lockdown in New Zealand. Schools are closed, and businesses. Only "essential services" are allowed to remain open (pharmacies, doctors, supermarkets). We're not permitted to mix with anyone outside our household "bubble". Who you were with last night is who you're gonna stay with for the duration.

One household member is to be appointed to shop for food, etc. No travel is allowed outside of your neighborhood (except for essential services and their workers). But going for walks, jogging, skating in your neighborhood are encouraged. Cycling is allowed too.

Cyclists here are in seventh heaven - they have empty roads all to themselves.

I'm looking at the growth curves, to see if we go the way of Japan and Singapore or whether we head towards Europe/US. It will be an interesting test case to see the effect of very early-applied social distancing interventions. We are getting in early in a relatively sense, because there are still relatively few cases here (260 odd, and no deaths). Will post tomorrow to see if the curve is flattening (although it might be too soon to see results just yet)

 

[Mij]

Our streets in the city are deserted, you can park horizontal.

 

[Wonko]

Our streets in the city are deserted, you can park horizontal.

It's been a very long time since I had a car but I'm fairly sure that parking it vertically was unusual at that time, frowned upon even, but your post suggests that being able to park horizontally is now considered 'unusual'.

 

[Mij]

Sooooooo yesterday . . .

 

[Adam pwme]

on BBC South today last night
9.44 - 10.50
https://www.bbc.co.uk/iplayer/episode/m000gqpk/south-today-evening-news-25032020

this explanation is closer to what they should be broadcasting regularly.

@Adam pwme

Thanks Sly. That's excellent. Will see if I can download it.

 

[FMMM1]

I agree. This makes no particular sense. I think it was intended to give an idea of risk. But it is hard to see how it can be based on evidence. I have a suspicion it was largely intended to reassure people that getting close to a passer by need not induce panic. That advice had clearly been turned around - we are not supposed to get within 2 metres for however short a time now.

Edit: From the comment on Hong Kong policy it rather looks as if 15 minutes was intended to be the time talking to someone with the virus needed to be darned sure you got it too!

There is a 15 minute time period in this article:
"In Hong Kong, “close contact” means fifteen minutes at a distance of less than six feet and without the use of a surgical mask; in Singapore, thirty minutes."
[https://www.newyorker.com/news/news-desk/keeping-the-coronavirus-from-infecting-health-care-workers]

So yes it was the basis to decide whether to quarantine ---not sure if they had a control "e.g. walk past within 2 metres) group (joke)!

 

[Sly Saint]

First day of lock down in India; Police are enforcing the strict rules imposed on 1.3 billion people
https://www.bbc.co.uk/news/av/world-52044058/coronavirus-first-day-of-lockdown-in-india

 

[FMMM1]

I think Fauci gets the Italy dynamics wrong. If it was due to masses of Chinese tourists there would have been hotspots in Rome, Venice, Pisa, Florence as well as the relatively less popular Milan. I see the problem as simply the expansion of a single case-based outbreak (maybe a coach load but why was that never picked up?) at a time when people were not even thinking of the diagnosis.

I was in Milan before Christmas and needed directions to a Pizza place (I know stereotypical) I asked the first person we bumped into, a Chinese student! I think there are very close links between Milan and China (textile industry/textile design/fashion?). I'd have a random guess at Chinese students returning to Milan after the Christmas break.

 

[FMMM1]

One virus particle has to be enough, although it may be that nearly all serious Covid19 depends on a larger dose, to get the process started before immunity kicks in.

It must all be a matter of statistics and the fact that spouses quite often do not get infected must mean that the vast majority of the time virus particles from someone breathing near you do not reach you nose or mouth and latch. I see it as a bit like birch tree seeds. One seed will grow a tree but even close to a birch tree shedding tens of millions of seeds in a season nothing may grow at any particular spot.

I think the hand washing is important because your hands have about a hundred times the surface area of your mouth and nose and we keep rubbing our mouth and nose with our hands. The chances of getting virus on your hands is much greater than getting it on your lips. Hands also touch all the surfaces that may be a thousand times larger and finely coated with virus.

If just walking past someone was a significant risk then the R number for transmission would be about 100. It seems to be about 2 so the chance must be small (and far less than 1/50 because it is not that simple! R relates to everyone infected over a period of many hours or some days.).

Spoke to a neighbour (doctor) earlier --- droplet transmission and surfaces touched by other people --- just like you are saying.

I recall your comment about the hand rail --- my neighbours was the petrol pump nozzle!