Corona virus epidemic

January 31, 2020

I keep being asked about the coronavirus, and have been noncommittal about it, because there was not a lot of information to go on.

But now there is more information, so I will say a little.

1.  Anthony Fauci, head of the NIH's infectious disease branch, said the death rate is 1-2% and that this may be compared to an average influenza virus, which has a mortality rate of 0.1%.

If his numbers are based on reported estimates that 100,000 are infected and 1500 have died, his mortality estimate is too low.  You have to look at one whole group that was infected at the same time, then look at the total number of them who died, after the rest have recovered, to estimate mortality.  I am not aware of good stats on this yet.

2.  I heard the R zero number (an estimate of how many people are, on average, infected by a single person with coronavirus) is 3-4.  If so, the coronavirus is less infectious than measles and roughly as infectious as many other infections.

3.  What is the mechanism by which the virus kills?  This needs to be answered in order to devise effective treatments.

A Chinese article published this week suggested that cytokine levels are higher in coronavirus patients than controls.  But are patients dying from cytokine storm?  This was not revealed.

During the 2009 swine flu pandemic, pregnant women in Australia were reported to be dying as a result of thick, infected mucus plugging their airways, preventing gas exchange in the lungs.  (Gas exchange involves carbon dioxide leaving the blood and oxygen entering the blood as it traverses the lungs.)

While there was not much media attention given to the topic, the use of ECMO to temporarily fill in for the lungs, until the body can repair itself, saved a number of lives then.  ECMO stands for extracorporeal membrane oxygenation, in other words, oxygenating the blood using a machine.

There are not many of these machines around, likely only a few in every state.  If patients with good lungs are dying due to temporary respiratory failure, then ECMO might be a lifesaver.

Here is a list of ECMO sites.  822 centers with the devices are listed.


UPDATE Feb 8:  from a Straits Times interview with a doctor of acute medicine at Wuhan University south central hospital:

"How do you treat serious and life-threatening cases?

Peng: For serious and life-threatening cases, our main approach is to provide oxygen, high-volume oxygen. At first noninvasive machine-pumped oxygen, followed by intubated oxygen if conditions worsen. For life-threatening cases, we use Ecmo (extracorporeal membrane oxygenation, or pumping the patient's blood through an artificial lung machine). In four cases, we applied Ecmo to rescue patients from the verge of death."

4.  Is this novel Coronavirus something that escaped from a lab, or perhaps was deliberately released?  You know as much as I do about that one.  If sufficient information is available in the future, I will comment on it then.

So how good is the flu shot really?/ Clinical Infectious Disease

CDC says flu vaccines prevent flu, on average 40% of the time, but even if you do get flu, the vaccine makes it less severe.  But when these two claims were tested in Australia, neither was found to be true.  The Australian study found  that (in 17 hospitals over 7 recent flu seasons) there was no reduction in flu symptom severity in those who had been vaccinated versus those who had not.

The study also found, using a case-control design, that the vaccine averaged 31% effectiveness at preventing the flu.  Earlier flu studies have been rightly criticized for ignoring the "healthy vaccinee"  effect.  The healthy vaccinee effect refers to the fact that, overall, elders who receive flu vaccine in the US are a healthier group than elders who do not receive flu vaccine... possibly because their doctors felt they were too frail to risk a side effect.  If the authors did not take this factor into account (and the whole article is behind a paywall so I could not read the details) then the actual efficacy might be considerably lower.

Influenza Vaccine Effectiveness against influenza-related mortality in Australian hospitalized patients:  a propensity score analysis.

Monica L Nation, Robert Moss, Matthew J Spittal, Tom Kotsimbos, Paul M Kelly, Allen C Cheng on behalf of the FluCAN Investigators

Clinical Infectious Diseases,  https://doi.org/10.1093/cid/ciz1238

Published:  06 January 2020

Background

Data on influenza vaccine effectiveness (IVE) against mortality is limited, with no Australian data to guide vaccine uptake. We aimed to assess IVE against influenza-related mortality in Australian hospitalized patients; assess residual confounding in the association between influenza vaccination and mortality; and assess whether influenza vaccination reduces the severity of influenza illness.

Methods

Data were collected between 2010–2017 from a national Australian hospital-based sentinel surveillance system using a case-control design. Adults and children admitted to the 17 study hospitals with acute respiratory symptoms were tested for influenza using nucleic acid testing; all eligible test-positive cases were included, and a subset of test-negative controls. Propensity score analysis and multivariable logistic regression were used to determine the adjusted Odds Ratio (aOR) of vaccination, with IVE= 1–aOR x 100%. Residual confounding was assessed by examining mortality in controls.

Results

Over eight seasons, 14038 patients were admitted with laboratory-confirmed influenza. The primary analysis included 9298 cases and 6451 controls, with 194 cases and 136 controls dying during hospitalization. Vaccination was associated with a 31% (95%CI: 3–51%, p=0.033) reduction in influenza-related mortality, with similar estimates in the National Immunisation Program target group. Residual confounding was identified in patients ≥65 years old (aOR: 1.92 (95%CI: 1.06–3.46); p=0.031). There was no evidence that vaccination reduced the severity of influenza illness (aOR: 1.07 (95%CI: 0.76–1.50); p=0.713).

Conclusions

Influenza vaccination is associated with a moderate reduction in influenza-related mortality. This finding reinforces the utility of the Australian vaccination program in protecting those most at risk of influenza-related deaths.