COVID 19: What's working, what's not, and why.

 COVID 19: What's working, what's not, and why.

--by Stewart Vriesinga                                                                              

 

Over the past year my understanding of COVID-causing novel corona virus SARS-CoV2 has evolved considerably. So have policies, mitigation measures,  and Public Health orders, not to mention the virus itself. Some of what we thought we knew was wrong, or has been called into question. Other things we never knew, and are still learning. Consequently some policies have become incomprehensible, contradictory, political, ineffectual, or, at best, based on old debunked science. At worst policies are more concerned with an existential threat to the economy and the popularity of elected officials among their support base, and less concerned with the fate of their most vulnerable citizens and those charged with looking after them.. 

I've tried to keep up with the science and tease out the most current, credible, science-based bits of information from no small amount of baseless conjecture, wishful thinking, the biases introduced by competing economic priorities, and far-fetched conspiracy theories. I am no expert, but I have tried to suss out those who are, and modify my opinions accordingly. While most were not, some authors and studies were very compelling. That said, this is nonetheless an opinion piece. You've been forewarned. 

In my opinion some things are not getting the attention they deserve, while other things are getting far more attention than they deserve. Fomite transmission and outdoor transmission would fall into the latter category; while they may play a role in transmission they are not the primary sources of transmission.  In the former category we have aerosol transmission, super-carriers, and super-spreader events, all of which do play a major role in transmission. The opportunity costs of putting too much emphasis on less effective containment measures comes at the expense of fully pursuing the most effective, all be they less popular, measures. I fear that the most effectual measures are taking a back seat to more popular, more convenient, but less economically and politically costly, and less effectual measures.    

Here is what I think we now know:

We know that the primary mode of transmission is through very fine aerosol droplets that can remain suspended in the air for hours. While time and greater distance from the source results in increasing dilution, even to the point of effectively neutralizing it, there is no magical cut-off distance past which this virus cannot travel --not six feet, not thirty-six feet, not one hundred and thirty-six feet. (See First10EM: COVID-19 is spread by aerosols: an evidence review )

We also know that transmission depends on the amount of aerosol in the air, and how long someone spends in a space where there is significant airborne virus in the air. Spending a very short period of time --say ten minutes or less--in a space where there is airborne virus is not likely to result in transmission.  On the other hand, entering and spending time in a poorly ventilated crowded space, even shortly after all the people have left, can and does cause transmission. Inversely, outdoor, sparsely populated and well ventilated spaces are highly unlikely sources/causes of transmission. 

Furthermore, there is compelling evidence suggesting that we are not all equal opportunity spreaders. A very small number of people have a very high viral load, and can easily infect numerous other people, even if they themselves are asymptomatic or presymptomatic.(1.)  Such people are sometimes referred to as "super-spreaders". There are no known markers --no way of knowing who the super-spreaders are--without testing and measuring the viral load of each particular carrier. Most people infected with the virus do not go on to infect anyone, or infect very few people. Only 2% of carriers carry 90% of the virus, and ostensibly do 90% of the spreading. (See Medical Press: 2% of people carry 90% of COVID-19 virus, and roommates are safer than you think, also see The Colorado SUN:  How CU scientists identified coronavirus “super-carriers” by collecting gallons of students’ spit.)

Only broad-based asymptomatic screening and testing can identify presymptomatic and asymptomatic cases of COVID infections. Only measuring the viral load of each known carrier will determine whether or not positive cases are highly-contagious super-spreaders, or whether, like most positive cases, they have a very low viral load and therefore are unlikely to infect anyone.  Therefore contact tracing, usually considered to be the most effective way of learning who each positive case may have infected while contagious, should be used primarily to determine where and by whom a positive case became infected in the first place. The latter requires tracing positive cases back to the initial infection, some five days before they had incubated the virus long enough to test positive, and up to fourteen days or more before they began to show symptoms. (If they ever go on to show symptoms. Some 40% of carriers do not, especially if they are young, although that may no longer be the case with some of the new variants of concern (VOCS.)).(See BBC Covid test-and-trace: Is backwards contact tracing the way forward? )

From the diagram above we see the initial transmission has occurred days before a person tested positive, and even longer than that before they become infectious and/or display symptoms. The contact-tracing challenges and resources required to trace an infection back to its source --backwards contact-tracing--are far greater than the challenges of determining who an infected individual may have gone on to infect if/while they were contagious. The former requires identifying all contacts in the eleven or so days before the positive case was identified; the latter is only concerned with the four or five days that a positive case may have been at large spreading the virus. Yet, if the objective is to eliminate rather than merely manage community spread, backwards contact-tracing is the only way this can be done. Forward contact tracing is only likely to identify one or two positive cases, most of whom will not transmit the virus to others. The source of transmission must be traced to either a super-spreader event (as described above), or a super-carrier (also described above), or worse, some combination of both. Identifying those exposed in a super-spreader event, or to those exposed to a super-carrier, or both, will enable contact-tracers to locate and isolate large numbers of COVID carriers, some of which may also be/become super-spreaders. Despite its challenges backwards contact-tracing is by far the most effective tool we have to eliminate rather than merely manage community spread. Measuring the viral load of all carriers could identify super-carriers.

Below is a diagram of the most prevalent forms of transmission:

 

Super-carrier "A" is spreading the virus (bottom left). Many of those he/she encounters become infected. Most of those infected do not go on to infect others, although they may go on to infect members of their own household bubbles and perhaps one or two others. This pattern is repeated in every cluster that super-spreader "A" comes into contact with. Unless super-spreader "A" comes into contact with a very large group of people in a crowded, usually indoor, poorly ventilated space, where they could end up infecting almost everyone in that space --a super-spreader event triggered by a super-carrier. Even though 98% of those infected at a super-spreader event will not become super-carriers themselves, about 2% of them will. In a group of one hundred, two people are likely to become super-carriers in their own right, infecting clusters (bubbles) and triggering super-spreader events of their own. (Super-spreaders "B" and "C" above.) For these reasons eliminating rather than managing community spread must focus on using backwards contact-tracing to identify large numbers of carriers resulting from super-spreader events, and by avoiding all gatherings that could potentially become super-spreader events. Such gatherings include church services, sports events, weddings, funerals, other large social gatherings, etc., but most transmission we now know occurs in workplaces. Gatherings of so-called "essential" workers should wherever possible be eliminated altogether, unless they are indeed essential, and all "essential" and service-sector workers should be routinely tested and vaccinated, and offered the supports necessary for them to stay at home if they feel at all sick or have potentially been exposed to someone else who is infectious.

Out of an abundance of caution we may continue to sanitize surfaces to reduce fomite spread, put up plexiglass barriers in our workplaces and businesses, maintain a distance of six feet or more from others, perhaps even outdoors, all to mitigate the likelihood of droplet spread. But none of these measures prevent aerosol spread, and should never substitute for eliminating aerosol spread. Aerosol spread is the primary way in which COVID spreads. It usually occurs during a prolonged period of time --ten minutes or more--in a workplace or other indoor, crowded or recently crowded, poorly ventilated space. Masking reduces the wearer's chances of both becoming infected, and of transmitting the infection to others, both in the case of aerosol as well as close-proximity larger droplet forms of transmission.

The effectiveness of vaccines of preventing the spread is often over-stated. The efficacy rating of vaccines is a measurement of how seriously ill a vaccinated person is likely to get. It is not a measurement of how likely they are to become infected or transmit the virus to others. Two doses of Pfizer or Moderna means that recipients are 90% likely to be protected from serious illness resulting in hospitalization or death. They are likely to remain asymptomatic, regardless of whether they are infected or not. Even one dose of Pfizer or Moderna yields 80% protection. AstraZeneca is rated at 76 % for one dose, and 81.3 % for two doses. Johnston and Johnston only requires one dose, with an 85% efficacy in preventing severe COVID-19,and 100% efficacy in preventing hospitalization or death caused by the disease. As to the efficacy of any of these vaccines in preventing infection or transmission altogether:

“While COVID-19 vaccines authorized in Canada have demonstrated efficacy against symptomatic illness, hospitalization and death, there were only limited data on their ability to prevent asymptomatic infection or to prevent transmission to others,” said André Gagnon, spokesperson for Health Canada, in an email. “While the Department is aware of this study, until there is more evidence, continuing adherence to public health measures to protect those around you remains necessary.”

--source Global News

 

Vaccines, often touted as the solution to the epidemic, have in fact not been proven to prevent infection or transmission. Without a doubt they can, do, and have saved a lot of lives, and it is incumbent on everyone offered a vaccine to get one. But, with or without vaccines, COVID will continue to spread as long as there are those capable of becoming infected and spreading the virus, including those who have been previously  vaccinated and/or recovered.  Furthermore, the efficacy of vaccines in preventing disease is diminished over time. Its efficacy after six months is largely unknown. Finally, the efficacy of vaccines against some of these new VOCs also remains largely unknown, and in all likelihood even vaccinated/recovered people will require booster shots from time to time for continued protection from severe illness caused by VOCs and/or a decline in the  immunity vaccines conferred on previously vaccinated individuals. Some preliminary anecdotal evidence suggests that vaccines may indeed somewhat reduce the likelihood of infection and transmission, but their efficacy in this respect remains largely unknown, so masking, physical distancing, etc. remain in place.

All this to say that the proliferation of COVID will continue well into the foreseeable future, and our best course of action is to focus on the elimination of aerosol spread. Measures should include efforts to minimize large congregate indoor gatherings, efforts to ensure that everyone attending such a gathering is wearing a mask, has been screened including using asymptomatic testing, and all in attendance have been fully vaccinated.  We must also use backwards contact-tracing to identify and isolate each and every carrier and potential super-spreader.  We must not fall into the temptation of merely managing the spread based on available ICU beds, human resources, and economic and political considerations. Only the complete elimination of the spread will ensure our collective physical, mental, economic and political well-being, and allow things to turn back to 'normal'. Preferably not the 'normal' of the past that has left, and continues to unnecessarily leave large sectors of the population extremely vulnerable; a vulnerability further exacerbated by containment measures that further increase inequities, often punishing the most vulnerable without achieving any real and lasting reduction in transmission.

My concern is that too often we are putting our desire for economic recovery ahead of public health. The desire for economic survival and recovery must not be allowed to eclipse the need to end the proliferation of this virus. Public health measures that are deemed to adversely effect economic activity are too often eschewed in favour of half-measures that do little to end this pandemic. For many governmental  financial supports aren't enough; economic recovery requires a return to a pre-pandemic steady supply of cheap low-wage labour. For many the existential threat is not COVID; it is losing the source of cheap labour on which their businesses rely. This has been a major consideration for governments from the beginning. Businesses are continuously being bailed out, both directly and by ensuring them access to a continued supply of cheap labour. A guaranteed supply of cheap labour is achieved by; denying low-income workers sick leave; by failure to shut down non-essential unsafe workplaces; by keeping schools open so as to ensure that "essential workers" children's  needs are looked after as their parents continue to work; by allowing employers, not employees, to determine whether or not their work is essential; by providing the Emergency Wage Subsidy to employers rather than directly to employees; by providing rent subsidies to landlords rather than tenants; by refusal to vaccinate and test essential workers, etc. 

 

Even so, some people are still concerned about access to cheap labour.  They have names: New Brunswick's Premier Higgs,  Alberta's Premier Jason Kenney, Manitoba's  Premier Brian Pallisterare, Conservative finance critic Pierre Poilievre, and The C.D. Howe Institute, to name but a few (2)--all calling for an end to emergency benefits, not for large and small businesses, but  for the working poor. They want to end the benefits because such benefits --namely a paltry $2,000/month CERB payment--are "a disincentive to work", and are making it difficult for businesses to recruit workers. Businesses accustomed to paying their workers sub-subsistence wages are exercising an inordinate amount of power and influence, not to protect us from this pandemic, but to protect themselves from having to pay fair wages to their workers. This is not about protecting people from COVID; this is not about getting us through an 'we're all in this together' pandemic; it's about protecting employers from social justice --from having to pay their workers a living wage. They want economic recovery, complete with all its social and economic injustices. It is absolutely abhorrent! Yet it seems to be the driving force for much of government policy in the midst of this horrific pandemic; a pandemic that continues to present an existential threat to the lives of millions of society's most vulnerable members while it runs our front-line healthcare workers into the ground.

What happens next will be determined by the most influential. Alas! It doesn't look like those most adversely impacted --the  most vulnerable, the working poor, the  essential workers--will be the decision-makers here. 

CONTACT TRACING, UNIVERSAL TESTING, AND OTHER IMPERATIVES:

 

CONTACT TRACING, UNIVERSAL TESTING, AND OTHER IMPERATIVES:

--by Stewart Vriesinga

Contact tracing of positive COVID cases can be used to: 1.) Identify the person/situation in which a known positive case contracted the virus, and 2.) Identify the people and situations in which a positive case could have passed the disease on to others. Of these two objectives, without taking away from the importance of the latter, the former is probably the most useful in controlling the spread of the virus. It is also the most difficult. Why?

There is a considerable delay between when a person becomes infected and the relatively short period of time in which an infected person is capable of spreading the virus to others.

 

Here we see that the period of time in which an infected person is the most contagious begins two or three days before the onset of symptoms (if they develop symptoms at all), and for a few days after the onset of symptoms. However, contract tracing only intended to identify who a carrier may have infected is not enough. Furthermore, infected contacts will probably test negative for the first five days after transmission, so all contacts should self-isolate for five days before getting tested.

Contract tracing intended to identify where and from whom an infected person may have contracted the virus, though very difficult, is essential. Given that the incubation period –generally assumed to be as long as 14 days—the number of contacts from which an infected individual may have come into contact with is likely to be far more numerous than those to which they may have passed the virus. Contract tracing over this lengthier period of time (sometimes called backwards contact tracing) is the only way of determining where and from whom an individual may have contracted the virus. Eradicating the virus requires identifying the sources as well as those who may have become infected. We now know that much transmission occurs in outbreaks –so-called super-spreader events in which airborne aerosol (as opposed to the small droplets that fall to the ground within six feet) spread the virus to almost everyone who spends fifteen minutes or more in a crowded indoor gathering in a poorly ventilated social or work space. (Someone entering such a space even after it has been vacated can become infected by aerosol lingering in the air.) Backwards contact tracing –identifying the sources of transmission—help identify instances in which large groups of people may have become infected --large groups which may have remained undetected without backward contact tracing. Probable cases have to be identified, isolated, tested, and if needed, isolated. Transmissions that were not traced to their source –often to referred to by that ambiguous term “community spread”--result in any number of individuals continuing to spread the virus. To eradicate, or even curb the spread, all carriers --asymptomatic, presymptomatic and symptomatic—must be identified and isolated. 

The contact tracing necessary to do this requires an immense amount of resources. If the total number of cases are allowed to become too high, such contact tracing becomes all but impossible. That is where we are at now. Government measures to date have only sought to reduce the numbers enough to not overwhelm the healthcare system, rather than eradicate the virus or even reduce the numbers enough to allow for comprehensive contact tracing. When contacts are not identified, contacted and isolated within two or three days things spin out of control. They are now out of control. Even in-between the first, second, and third waves things were never really under control, because rather than allocating more resources to testing, laboratories, contact tracing, etc. governments chose to discourage those things in order to avoid overwhelming Public Health's existing capabilities. Only the prospect of overwhelming hospitals was enough to induce them to act, and then it was always too little too late. Hence we are in this endless ineffectual cycle of closures and reopenings.

There are better alternatives: We could have done, and still must do universal asymptomatic screening/testing in all workplaces, schools, etc.; Using the less invasive, less reliable, but more economical saliva tests, followed up with more reliable nasal swabs in the case of positive results; making much more use of economical waste-water testing, which, while it can't identify individual carriers, can provide entire communities with an early warning of any increase in the prevalence of the virus in their community, including among asymptomatic and presymptomatic community members, as well as identify which variants are present in a community. Waste-water testing has been used effectively for over a year now in some countries as well as some jurisdictions here in Canada.

Furthermore, given the evolution of new, more contagious, and deadlier variants, some of which are more resistant to current vaccines and infecting younger people; given that we don't yet know the efficacy of the vaccines currently in use at preventing infection and transmission (so far we only know that they're very effective at preventing disease and death after infection); given that the threat of COVID may be with us for a long time to come; for all these reasons it is essential that we put more effort and resources into eradicating and curbing the spread of this virus, rather than basing decisions on unsubstantiated, overly-optimistic presumptions that stop-gap measures will suffice until herd immunity sets in and everything goes back to normal through the use of vaccines. Because, however abhorrent it may seem, in all likelihood things will not go back to normal in the foreseeable future. The virus and its constantly evolving variants will always be one or two steps ahead of us. Viruses, which replicate by the billions on a daily basis, will not take billions of years to evolve, adjust, adapt to, and circumvent vaccines, even if if we are producing them in unprecedented record time.