Viral load - can someone explain?

[OverUnderSidewaysDown]

Can someone with expertise explain viral load? I used to understand it as meaning how much virus an individual was carrying and shedding , i.e. how infectious they were to other people. But in recent days I've heard it described as meaning how much virus a person is exposed to, and used as an explanation for why doctors and nurses are getting the virus more than other people.
Which is correct? A doctor could catch it from just one patient, but if they treat one hundred patients does their susceptibility increase?

Thank you to all who have taken the time to explain in such detail.

@sashh

I love that explanation.

This is not being mentioned in the news, people need to know that if they have symptoms they should isolate within their house to prevent their family being exposed to a high viral load.

Thanks so much for taking the time to explain.

www.thelancet.com/action/showPdf?pii=S1473-3099%2820%2930232-2

I don’t know about this but an NHS consultant posted this link on Facebook re viral load

www.bbc.co.uk/news/uk-51506729

The person with the symptoms should stay in a well-ventilated room with a window that can be opened, and keep away from other people in the home.

The clue is the SELF in self isolating. You can't isolate with anybody else. But because self distancing within a household is incredibly hard to do and the virus may have already been given to somebody in close proximity before you realise you have symptoms, you also have to isolate as a household. So 7 days SELF isolating from initial symptoms and 14 days HOUSEHOLD isolating (unless you live alone). I think the term "self isolating" is being used by most people to mean both of these things, but the 7 days and 14 days are not the same, even though the days will mostly overlap.

I agree we need to self isolate, I’m just not sure this message is being put across in the conferences. I think most people would assume if one family member gets it they all will so wouldn’t know they needed to isolate from their family group.

The reason for being in a well ventilated room with a window is that with droplet transmission you are exposed to more of the droplets/virus in a space where the air is not being circulated. So in a hospital environment or close proximity without good ventilation and air circulation (many workplaces, supermarkets and bus/train/tube for instance) you are both more likely to get the virus and more likely to get a high viral load.

@DentalPatient

Yes I think some of these messages are being lost, but from a governmental Macro perspective HOUSEHOLD isolating works better than SELF isolating within households. Also it means that people won't try to justify exposing other people (because their family member was self isolating so they don't need to) because in reality self isolating will be incredibly hard if not impossible for some households to do due to shared facilities etc.

This is very important information!

Most people can not retain that many instructions at once, so the government should be focusing on what is the clearest and most effective. If anything the last few weeks have shown that we need things to be explained more simply and in the fewest instructions. Give people too many things to think about they will mis prioritise or mis remember and start filling the "gaps" themselves with misinformation.

It's like telling a toddler not to hit or kick. So they push instead and then don't understand why they are in trouble. But once they understand not to hit or kick, then it becomes easier to get them not to push (or pinch, or bite). And why once their comprehension grows as a pre schooler they can begin to be taught not to shout or lie or snatch things. You try and give a child all that information at once they are overloaded, the rules become murky, they become confused and start doing the worst behaviour because you are trying to get them not to do things that matter less. I think once people get a good grasp of the basics then the government may be able to give more in depth messages and further guidance.

But then adults are much worse at doing what they are told and much more stuck in their ways. One of the biggest issues we are facing is people not trusting the government and not doing what the government tell them. But if they won't do that and ALSO won't take authority from health alternatives like the WHO or listen to their families, then the next steps is sanctions. Just like with behavioural modification in a child. "Don't hit, be kind." Appealing to their better nature. Then "if you hit you go to time out." Threat of a sanction. We like to think we are all much more advanced than that but ultimately we are all just toddlers trying to make sense of new rules and having some meltdowns in the process!

Ive been very grateful for the answers on this thread.
I do understand what you're saying in that last post , Another, but I think people would be more prepared to obey the rules if the reasons behind them were explained in clear simple terms. Just the basics that you've given here, about increased exposure making your chances worse through viral load (overload?) would be so helpful if it could be publicised.
"Too much virus can kill you" kind of thing.

@OverUnderSidewaysDown

I think the problem is that a clear statement on the effect of viral load cannot be made because it's not just the viral load but individual immune response. As soon as people hear people are at a higher risk if they have underlying health conditions they switch off (unless they know they have underlying health conditions). There have been a lot of warnings that this effects healthy younger adults too but the message is not getting through, because these have mostly been frontline health workers and people think, well I don't work in a hospital so I'm ok. As soon as people think it doesn't effect them they switch off.

Can anyone find the graph that demonstrates how long to self-isolate in a family? It was pink and I think I saw it on mumsnet but I can't find it anywhere now.

...and some load and shedding patterns of mild v severe cases

Maybe we need some sort of graphics or cartoon type thing to to help people form a mental picture of how viral load can increase in a room where lots of people are coughing and sneezing etc, and then show that this interacts with the underlying state of health of people.
Just trying to make the point that giving information visually can sometimes help people to process it and integrate it with what they already know.

@AnotherMurkyDay Yes there is correlation between repeated exposure, high viral load and unexpected poor outcomes, but as with most of the covid 19 science most of it is somewhat speculative because there are a lot of unknowns and all research is in the early stages. That's what's so worrying that we really can't predict things that clearly as we don't know the patterns yet

Exactly. More is being learnt all the time. Also your point about it not necessarily being about the amount of virus contracted, it's what our body does with it.

Just to balance out links to other articles on here, see this one
www.newscientist.com/article/2238473-you-could-be-spreading-the-coronavirus-without-realising-youve-got-it/

People with mild or no symptoms can have a very high viral load in their upper respiratory tracts, meaning they can shed the virus through spitting, touching their mouths or noses and then a surface, or possibly talking. Even people who don’t feel ill occasionally cough or sneeze.

This is what is important for people to know, and why we should assume that anyone - at least those outside our home might have it.

I can’t believe how important this is despite it not being publicised!

It is important to realise that people with no symptoms or mild symptoms can also transmit, @HIVpos. Good point. There is also evidence that viral load may peak before the onset of symptoms:

www.medrxiv.org/content/10.1101/2020.03.15.20036707v2

The papers referred to in the New Scientist article aren't contradicting the Lancet article. I think the article is poorly worded and not a good representation of what the research they link to shows.

To summarise all the papers:

1. Severe cases of COVID-19 appear to have a higher viral load than mild cases.

1. The initial viral load (how much of the virus you are infected with) seems to be one of the factors that affects outcomes. The higher the initial viral load, the more likely you are to have severe symptoms. This is important because it means not only can we take measures to prevent the transmission of the disease, we can take measures personally to reduce the level of the virus we might be exposed to to reduce the likelihood of severe symptoms eg properly observing self isolation if a member of the household has any symptoms, keeping up good hygiene practices like hand washing in the home during lockdown even if no one has symptoms yet (see below).

1. Viral load in the throat appears to peak before the onset of symptoms so many transmissions will occur before a person knows they have the virus.

1. People with mild or no symptoms can still pass on the virus. They may even be the main drivers of the epidemic as they are (were before lockdown) out and about coming into contact with people rather than at home in bed.

Just musing and there’s very little that could be done about it right now but could it be possible that HCP’s are inadvertently adding to the danger?

They’re at such a high risk anyway but passing on more virus to already ill patients seems like it’s a recipe for a bad outcome.

Again, I know there isn’t really a way around it at the moment but I wonder if in the future there could be measures implemented to rota and limit HCP’s contact with corona patients as part of the infection measures.

The papers referred to in the New Scientist article aren't contradicting the Lancet article.

I didn’t think it did. I came across both articles last night and only cited this one after seeing the other referenced on here. It was merely to show another example of ongoing research trying to understand how this virus ticks.

All interesting stuff and a lot more to come I’m sure.

Sorry, I misunderstood @HIVpos, I interpreted "balance out" as you meant show a different, opposing viewpoint.

@Cornettoninja

We should be regularly testing health care professionals (and as many other frontline workers as possible) and any positive test would mean 7 days out of the work force. Even with the test taking 2 days to come back, that would mean only 2 days of extra exposure/exposing time and 7 days less at highest viral load (even if they have no symptoms). There are other things like having the right PPE and protocols in place that would have meant this was dealt with better, as well as not running our hospitals at such high capacity. Having as much of the workforce working from home would be another positive in future to present rapid spreading of diseases and less flying, although these would be unpopular. I think more parents should stay at home too ideally, but it's never popular to argue that single parents should be supported to look after their own children even if that means not working. We always put the economy over health and for most people most of the time that works. But not now.