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🦘Cacatman's Personal Coronavirus COVID-19 Update Thread

Indoor vs Outdoors - 18.7 times greater risk
A preliminary report from scientists in Japan (which has not been peer-reviewed) suggested that the odds that an infected person "transmitted COVID-19 in a closed environment was 18.7 times greater compared to an open-air environment."

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Why Herd Immunity WON'T Work (in Australia, at least)
One of the more sincere questions I get asked by people grappling with the CoVID-19 pandemic is: “if the mortality rate is so low, why don’t we just aim for herd immunity. Surely that would be better than locking us all down?”
Herd immunity is the concept that if enough people are immune to a particular disease, either through naturally acquired immunity or vaccination, that the spread of the disease in the community is arrested, hence protecting vulnerable individuals like the elderly, babies, pregnant women and those with chronic health conditions.
The percentage of people that need to be immune to a disease in order to establish herd immunity in the community varies depending on the disease reproductive number. For CoVID-19 the percentage estimated to achieve herd immunity would be 60% of the population.
The current mortality rate of CoVID in Australia is around 1.7%. Worldwide case mortality is double this at 3.6%. But for the sake of simplicity let’s use the Australian mortality rate.
If 60% of the community needs to catch COVID-19 to achieve herd immunity, that means that 14.4 million Australians need to be infected. No problem.
1.7% will die of the disease. That’s 244,800 dead Australians.
But hey, 98.3% will survive, right?
But international figures show 14% of patients require hospitalisation due to extreme symptoms and complications. That’s 1.96 million Australians that will need admission to hospital.
We only have 62,000 beds available Australia-wide. So what happens to the 1.9 million Australians who need beds but can’t get the medical care to pull through?
But forget them...what’s important is that the really sick Australians get a bed, right?
International figures show that 2% of infected patients require intensive care support. That would mean that 280,000 Australians will require ICU admission.
We have 2378 ICU beds. What happens to the 276,000 critically unwell patients that cannot get an ICU bed?
Aiming for herd immunity in Australia would hence result in:
14.4 million infected Australians.
1.9 million severely infected Australians unable to get a hospital bed.
276,000 critically infected Australians unable to get an ICU bed.
Oh, and the 244,800 Australians that are going to die because ‘it’s only a 1.7% mortality rate’.
But, hey, at least we’ll establish herd immunity, right?
Except for that fact that all evidence points to waning immunity following infection, with antibodies waning after 3 months.
Herd immunity is not an option. Stay home, and stay sensible.
From Elaine Stevenson, Australian Infectious Disease Epidemiologist, who contacted me and is aghast by the Swedish approach:
“Herd immunity is a concept which only applies to vaccine preventable diseases as a measure of program efficacy.
It does not apply to the situation that we are currently in vis a vis COVID-19
We do not have enough follow up on the virus to be anything other than extremely cautious”.
- Sara Hassan Park

Schools & COVID-19
Spread between children is obviously possible, but after surveying some of the literature around it, I think the emphasis at the school should be focussed on ensuring that individuals treat themselves as possible asymptomatic carriers ie. by taking precautions - mask wearing, socially distancing, washing hands, not touching their face with possibly contaminated hands, not sharing foods and staying home if they have symptoms of being unwell. This is because between 16-45% of paediatric infections may be asymptomatic (from BMJ/French multi centre study).

A recent review of 7 published studies showed that the false negative rate of testing was as high as 67% if subject tested in the first 7 days, and still alarmingly high, even at the most optimum time to test ie. Day 8 post exposure (/Day 3 post commencement of symptoms).

Personally, I would only push to use COVID-19 testing as a tool to determine whether someone is safe to return to school if they had known/highly suspected close contact with a carrier, (< 6 feet for 15 mins) because of the alarmingly high false negative rate (up to 1/5 false negative rate even when conducted at the optimum time of 3 days post symptoms/8 days since exposure). I think the false negative rates would be even higher in children due to the difficulties posed with sample collection. But I admit that the cost, resource burden and current prevalence is also a consideration in this recommendation.��New continuous cough and fever are the most common symptoms of COVID in children, so I would recommend that anyone with these symptoms to stay home. I would also recommend to stay home if they are found to have loss/change of sense of smell/taste or diarrhoea. As Gordon, Joel and CDC have suggested, they should remain home until fever has normalised for 24 hours (or if diarrhoea, then 48 hours).

Some have suggested that children with just runny noses, sneezing and sore throat can go to school as long as they don’t have a fever (provided they have NOT been in contact with someone with known COVID-19 or someone who has COVID symptoms in their household).

Having said all that, several things are “on our side”. Children play less role in the spread of the virus (as compared to adults were they to be in the same environment. UCL meta analysis of more than 6,000 studies showed they were half as likely to catch coronavirus). They also seem to have less severe symptoms when they actually do get COVID-19, and they have a lower mortality rate as a group.

A Dutch study from June tested 3,500 children <6 yo who had symptoms of cough/SOB and 0.5% were positive ie. 1/200. That percentage was 14.3% in children who tested in the same period because they had been in contact with a COVID-19 patient.

In Australia, a study showed that there had been confirmed cases of COVID-19 in 9 children and 9 employees. 735 children and 128 employees had been in close contact with these patients. Only two other children may possibly have been infected by one of these 18 patients. No other teacher or staff member contracted COVID-19.

ACP Journals - False negative rates

1. Assaker, Rita, et al. Presenting symptoms of COVID-19 in children: a meta-analysis of published studies. BJA: British Journal of Anaesthesia.
2. Poline et al. Systematic SARS-CoV-2 screening at hospital admission in children: A French prospective multicenter study. Clinical Infectious Disease.

Back to school advice - American Academy of Pediatrics

Study of 50,000 Patients' Symptoms
According to study findings of 50,000 patients, this is the order of symptoms that COVID infected patients can experience:

1. fever
2. cough and muscle pain
3. nausea or vomiting
4. diarrhea


High false negative rates in PCR testing.
ie. just because you have a negative test, doesn't mean you actually ARE in fact negative!!! https://www.nejm.org/doi/full/10.1056/NEJMp2015897
Usually due to poor collection, recovery of virus at levels below the LoD of the assay and biological reasons such as absent/intermittent shedding.

Viral ran levels peak in oropharynx and the nasopharynx between 4-6 days after symptom onset and last 15-18 days

But in stool, it can last for over 4 weeks


False Positive Rates with PCR Tests
False positives are rare with the PCR test ie. sensitivity (false positives) is very high, despite low specificity (ie false negative rates)
This is due to the fact that the amplification of the RNA coronavirus fragments are amplified over multiple cycle thresholds (CT).
However, a positive PCR test doesn't equate to being infectious (which is important). Most labs check for 37 -40 cycles. This correlates to finding viral fragments, but not infectious people.

Suggestion is that CT be 30 or less for detection. Currently up to 90% of positives may not actually be infectious.


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