I – Coronaviruses
III – COVID-19 Immunity
IV – Special Populations (Elderly People, Children, Obese People and Healthcare Workers)
V – Containment, Mitigation, Suppression (The Hammer)
VI – The Dance
VII – Treatments and Vaccines
VIII – Masks
IX – How is Ireland Doing?
X – COVID-19 Worldwide


I – Coronaviruses

Coronaviruses are a family of viruses that infect mammals and birds. Seven of them are known to cause respiratory (nose, sinus, throat, lung) disease in humans:

Viral nomenclature is confusing: 2019-nCoV = 2019 novel coronavirus, also called SARS-CoV-2 because genetically it’s very similar to SARS. This means that SARS is now called SARS-CoV-1. The disease caused by 2019-nCoV is called COVID-19 (for Coronavirus Disease 2019).

All of the human coronaviruses have crossed over to us from other species. For a family of viruses that infects both mammals and birds it’s not terribly surprising that one of its biggest reservoirs is bats – the only flying mammal:

SARS spread to us from bats via civets, and MERS from bats via dromedary camels. SARS-CoV-2 originated in horseshoe bats but we’re not yet sure about the intermediary host (though many have speculated about pangolins).

When Europeans reached the Americas in the 1400s, they brought with them a plethora of diseases: smallpox, influenza, measles, cholera, yellow fever, malaria, lyme disease, tetanus, and whooping cough to name but a few. When these afflictions reached the locals, who had never been exposed (and thus had zero immunity) to them, they spread like wildfire, with devastating results – on Hispaniola they wiped out almost 95% of the indigenous population. The same principles apply when germs jump to a new species – they cause severe and widespread illness because the new hosts don’t have any built-up resistance.

Viruses hop from animals to humans the same way they pass between people: close contact with body fluids (mucous, blood, urine, faeces). SARS-CoV-2 jumped only once from an animal to a person and look at where we are now –  one in every two people on the planet is under some sort of order to stay home.

Bats are so often the first link in the chain because they can host multiple virus strains at once and blend them together to create new, more severe variants without ever getting sick themselves. As humans increasingly encroach on wildlife habitats, diseases have ever more opportunities to spill over into people. When Chinese researchers tested people who lived near the Shitou bat caves, nearly 3% of them had antibodies against bat SARS-like coronaviruses even though none had handled wildlife or had any symptoms. The only thing they had in common was that they had all seen bats flying in their villages.

It’s possible to plot global hotspots of emerging infectious diseases based on human population density, wildlife diversity and microbial (germ) diversity. The “wet markets” of Southeast Asia, where people, pigs, ducks, geese, chickens and occasionally other animals are in close proximity have been noted to pose a particular danger to public health by Webster 2004; Bush 2005; Greenfeld 2006; Lau et al 2007.

A great way to speed up the transmission of pathogens between species is to keep lots of different animals together in close quarters – on farms or in markets. Wet markets (so-called due to the regular hosing of floors to clear away blood and entrails) are establishments where one can purchase a variety of living or dead, domestic or wild animals. The animals are usually stacked in cages – bats on top of civets on top of rats. It’s difficult to disagree with the epidemiologist Jonathan Epstein, when he describes this as “just a gravitational exchange of faecal matter and viruses”. SARS-CoV-1 emerged from wildlife markets in Southern China and the first cases of SARS-CoV-2 seemed to be linked to a ‘seafood’ market in Wuhan.

Between these markets, our ever-increasing impingement on animal domains, and the regularity with which we transport ourselves, animals and their products around the world, new pathogens are emerging ever more frequently and further pandemics are inevitable.



HCoV Symptoms
Human coronaviruses and the diseases they cause. SARS = Severe Acute Respiratory Syndrome; MERS = Middle East Respiratory Syndrome.

Of the six human coronaviruses we knew about before 2019, four cause minor symptoms (colds, bronchitis) and infect the upper respiratory tract. This makes them highly contagious – it’s very easy to spread mucous that lives in your nose, as anyone who has every had a cold will attest. SARS and MERS on the other hand, primarily infect the lower respiratory tract (lungs), cause much more severe disease (SARS has a case fatality rate of 15% and MERS of 34%), but aren’t anywhere near as contagious. SARS-CoV-2 is a hybrid that can infect and replicate throughout the respiratory tract. This gives COVID-19 the lower respiratory severity of SARS and MERS and the upper respiratory transmissibility of the common cold – a lethal combination.

SARS-CoV-2 CellularSARS-CoV-2 enters your nose, mouth, or eyes and travels down to your lungs where it hijacks your cells and forces them to make millions of copies of itself. These clones then infect neighbouring cells or end up in droplets that escape the lungs and can infect other people.

Graphic Credit: Avesta Rastan
  • The Healthy air sacs (alveoli) at the top of the above infographic are full of inhaled air. The oxygen (O2) from that air can easily diffuse into the bloodstream, and the carbon dioxide (CO2) we have built up can easily diffuse from the bloodstream into the alveoli and be exhaled (this process, logically enough, is known as gas exchange).
  • The Infected alveoli have been invaded by virus particles. At this stage the infected person will have no symptoms but will be contagious – half of all COVID-19 infections are spread by people who don’t have any symptoms yet.
  • Of the Moderate alveoli, some are collapsing and others are starting to fill up. SARS-CoV-2 attacks the cells that produce an intrinsic fluid that keeps alveoli expanded and without it they start to collapse. By now the immune system is responding, causing fluid and white blood cells to leak into the alveoli, leaving less room for gas exchange. At this stage the infected person will have a cough, a fever, and feel short of breath.
  • The Severe alveoli have filled with fluid, proteins, white blood cells and scar tissue from the immune response. If this person is lucky they will be in hospital, maybe even in ICU. Even if they are fortunate enough to have access to a not-overrun hospital with a well staffed and functioning ICU they may still perish from a phenomenon known as a ‘cytokine storm‘, whereby the immune system goes into overdrive, attacking healthy cells in the lungs and even in other parts of the body, resulting in multi-organ failure (occurs in around 2.5% of COVID-19 patients).

    COVID Heart
    Adapted from: Potential Effects of Coronaviruses on the Cardiovascular System (JAMA)

Beyond the lungs, COVID-19 has effects on other organs, most importantly the heart: in Wuhan, of the patients who died from COVID-19, >52% had heart failure (vs. 12% of those who survived).

CStormSo why are some young, healthy people getting so much sicker from COVID-19 than from a typical viral pneumonia?
The first reason is to do with the cytokine storm, above. The second is to do with the fact that our usual drive to breathe isn’t governed by our blood’s oxygen level but by its level of carbon dioxide (CO2). Some free divers exploit this peculiarity by hyperventilating before a descent – blowing off lots of CO2 so they can spend more time under water before their CO2 builds up again and their brain starts reminding them to breathe (please note this is not recommended).

One of the things COVID-19 does is attack the fluid that usually keeps alveoli expanded. Without this fluid, the alveoli collapse, closing off spaces in your lungs where gas exchange can occur. Due to the concentration gradient between CO2 in blood and CO2 in air, you can still blow off your CO2 so your carbon dioxide levels remain normal, but your oxygen levels fall.

The physiology behind the next part is complex (probably explained at its most basic here) but the essential points are that:

Some people with low oxygen levels feel very short of breath while others don’t feel short of breath in the slightest. Normally with pneumonia you also have some discomfort in your chest because, being filled with fluid, proteins and white blood cells instead of air, your lungs are heavier and stiffer than normal. With COVID-19, when you can just have areas of collapse, your lungs aren’t heavy or stiff so this doesn’t happen (in the early stages, at least).


The people who have low oxygen levels but don’t feel short of breath, will almost certainly be breathing harder and faster without realising it. This actually worsens things – breathing harder causes more inflammation, which causes more alveoli to collapse and oxygen levels to plummet further. Over time, the inflammation generates more fluid in the alveoli, so the lungs become stiff, carbon dioxide levels rise and the asymptomatic people eventually do notice that breathing is an issue. By the time they present to hospital, chest x-rays reveal moderate to severe pneumonia, their oxygen levels are perilously low and they often end up on a ventilator.

Some people never feel alarmingly short of breath, even when their oxygen levels are so low as to be barely compatible with remaining alive – doctors have reported COVID-19 patients presenting with oxygen levels as low as 30% (normal is 94-100% and people usually lose consciousness < 75%.). That young people can present so late in the game dramatically worsens their odds of having only a minor illness, or even of surviving. This phenomenon may also explain cases of people with COVID-19 dying suddenly after not feeling short of breath.

That last part was maybe scary so here’s a cute little cartoon.

Let’s acknowledge here that 80% of COVID-19 patients experience only mild symptoms and get over the illness in a week or two simply by resting at home.


III – COVID-19 Immunity

Our immune systems are multifaceted – we have outer barriers like hair and skin (skin is a great barricade which is why there are messages everywhere reminding us not to touch places where we don’t have any – eyes, nose, mouth etc.), inner shields like mucous (snot), saliva and stomach acid, and on a microscopic level we have a multitude of defenders, which can mostly be divided into two troops: the innate responders and the adaptive responders:

  • Our innate immune response is immediate and tries to prevent foreign entities from occupying and colonising our bodies. It includes a cross-disciplinary army of white blood cells, proteins, and chemicals that endeavour to gobble up, destroy, or inform B and T cells about any and all trespassers.
  • Our adaptive immune response is an acquired reaction that tries to completely clear the infection by creating millions of T and B cells, tailor-made to take out the same specific assailant. It’s not instantaneous (peaking 4-7 days after infection) but it’s highly specific, and sustained long-term so that if we encounter the same bug in the future, our response will be much more efficient (this is the principle of vaccination). B cells are responsible for this memory – they* produce antibodies that stop the virus from replicating, while T cells destroy virus-infected cells.

ImmunesA lot of COVID-19 patients have gotten sick in two waves: seeming to bounce back before getting sicker. A Seattle study found that patients’ lungs appeared to deteriorate quickly around seven days into the disease, even in young, otherwise healthy people. This has been attributed to a cytokine storm. A cytokine storm is when the immune response spirals out of control and its weapons, designed to destroy foreign pathogens, are deployed against the body’s own healthy cells and tissues.

It takes about a week for T cells to build up in the body and when they do, you start to feel better but your condition may then rapidly worsen as the cells continue to proliferate far beyond the point at which they are helpful and become injurious. This is why antiviral medications only work well in the early phase of COVID-19 – later on, our own immune system is what tries to kill us.


IV – Special Populations (Elderly People, Children, Obese People and Healthcare Workers)

No guys, please wear masks and exit the dance party before your immune systems murder you. 🤦🏽‍♀️

Elderly people are particularly vulnerable because immune function declines with age. When the virus enters their upper airways, their immune systems don’t realise it. By the time they do, it has already gotten into their lungs and they are effectively trying to win a race by starting from the pit lane while their opponent is in pole position. Older immune systems are less capable of responding in a balanced way to a new virus and are much more likely to overreact (see: cytokine storm), causing more severe disease.
[On top of all this, white blood cell production is slower, and antibodies less able to bind to the virus and fight it off, making vaccines less effective in older people.]

There are also reports (from the US, the UK, Italy, Spain, and France) of children presenting with a hyperinflammatory response, similar to that seen in Kawasaki disease (an inflammation of arteries) and toxic shock syndrome (a rare but serious complication of bacterial infections… essentially a cytokine storm). This condition is known as Paediatric Inflammatory Multisystem Syndrome Temporally associated with SARS-CoV-2 (PIMS-TS) or Multisystem Inflammatory Syndrome in Children (MIS-C). Children account for 0.117% of COVID-19 deaths, so are at “unbelievably low risk” of dying from COVID-19. Some children with PIMS-TS have tested positive for COVID-19 and others negative. While it is not yet 100% clear whether this is caused by SARS-CoV-2 or something else, the general thinking at this time is that it’s a post-infectious trigger (like rheumatic fever) of COVID-19, causing the immune system to overreact 2-4 weeks after infection. PIMS-TS is potentially serious but incredibly rare.


Obesity is also a recognised risk factor – even early on, data showed that if you were young and ended up in hospital with COVID-19, you were more likely to be obese. Every time you breathe, you push your diaphragm (big sheet of muscle under your lungs) down towards your feet. If you have to push an extra 20-30kg of abdomen every time you breathe, it makes breathing significantly harder. This is a particular concern with COVID-19 – when the lungs are full of fluid, the diaphragm needs to work harder to get oxygen in and obesity restricts this. Fat also produces cytokines that promote inflammation, even in the absence of bacteria or viruses. When you superimpose a big battle with a new virus that your immune system hasn’t seen before, it gets hyper-activated and can result in, you’ve guessed it, a cytokine storm.

Healthcare workers are another special population, at one point accounting for 25% of Ireland’s COVID-19 cases. This is thought to be related to the “dose” of the virus that you first receive. The interaction between the virus and your immune system is a race between the virus trying to hijack your cells to make millions of copies of itself (and destroying the cells in the process) and your immune system trying to annihilate the virus. If the virus gets a head start (i.e. it’s a big dose), you accrue more copies of the virus and your immune system has to mount a bigger response for this tougher fight, heightening the risk of provoking the dreaded cytokine storm.

A 2004 study of 154 SARS patients, found that those with the highest initial viral loads had a 20-40% mortality rate, regardless of age or underlying conditions. Healthcare workers are exposed to the sickest COVID-19 patients who have the highest viral loads, so when they get sick, they get really sick. Patients who are agitated or delirious are often unable to comply with COVID-19 hygiene rules and may even pull at someone’s mask or goggles. With global supply shortages, healthcare workers are re-using personal protective equipment (PPE), while working longer hours than usual and generally getting run down, leaving them on the back foot when it comes to fighting off infections.

A 27-Year-Old Emergency Doctor’s Fight Against Coronavirus (NY Times)

So if you get COVID-19, then you develop immunity to it and can go back to work, yeah?
The short answer here is, unfortunately, no. After any infection, immunity can range from lifelong (smallpox, measles) to almost nonexistent (malaria, tetanus). With the MERS and SARS coronaviruses, antibodies stayed in the blood for a couple of years (two for SARS, three for MERS) but their power diminished with time. For the two seasonal coronaviruses most closely related to SARS-CoV-2 (HCoV-OC34 and HCoV-HKU1), scientists have inferred that COVID-19 immunity might last for a year or so and then decline. That is, if your B cells produce an appropriate level of antibodies.

In a Chinese study of 175 patients with mild COVID-19, 70% developed a strong antibody response, 25% a low response and about 5% developed no detectable response at all, suggesting they beat the virus with their T cell response alone (i.e. without developing antibodies). Without antibodies you will not develop long-lasting immunity. In other words (in this small study), 30% of proven COVID-19 patients had very few or no detectable antibodies and are likely not protected against future infection. Those with the lowest counts of antibodies were most likely to be the youngest patients. This is to say nothing of those asymptomatic people (depending on who you believe, anywhere from 5-80% of all COVID-19 infections produce no symptoms).
It’s worth noting that current antibody tests don’t tell you that you’re protected against reinfection.

THanks TweetBut we can transfuse the blood of people with COVID-19 antibodies into non-immune people, conferring them with immunity, right?
We can (the use of serum therapy for diphtheria earned the first Nobel Prize in Medicine and COVID-19 trials are ongoing) but this is not a viable population-level solution. One person can donate only 200-500ml plasma and it takes some time to recover. Over time their antibody count will drop so they will probably only be able to donate to a couple of people. Moreover, if only 70% of recovered patients have antibodies, your pool of donors is that much smaller.


[And then there is antibody enhancement: the fact that immunity to a virus can in some instances exacerbate an infection. In SARS-CoV-1, some found that infection with HCoV-229E seemed to prime the immune system such that the presence of HCoV-229E antibodies enhanced the ability of SARS to gain entry into the lungs…]

Again, here is probably a good place to emphasise that at the moment, our immune system is the most effective weapon we have against COVID-19.
Upwards of 80% of people who contract COVID-19 develop only mild symptoms.


V – Containment, Mitigation, Suppression
(The Hammer)

A police-controlled drone warns an elderly woman to wear a breathing mask during the coronavirus outbreak in China.

So how and when do we get back to normal?

The best answer to this is found by reading Tomas Pueyo’s excellent series of articles (particularly 1b), heavily excerpted from here on out:
1a Coronavirus: Why You Must Act Now
1b Coronavirus: The Hammer and the Dance
1c Coronavirus: Out of Many, One
2a Coronavirus: Learning How to Dance
2b Coronavirus: The Basic Dance Steps Everybody Can Follow
2c Coronavirus: How to Do Testing and Contact Tracing
2e Coronavirus: Prevent Seeding and Spreading

The real pains in the arse when it comes to COVID-19 are that, as of December 2019, nobody was immune to it, and that people can be infected (and infectious) for up to 14 days before having any symptoms. This means that on average, every person with COVID-19 gives the disease to 2-3 other people (known as ‘R’ or the transmission rate), such that cases grow exponentially: it took 67 days to reach 100,000 cases, 11 days to reach 200,000, and only 4 days to get to 300,000. Fewer than three months after it was first diagnosed, COVID-19 had infected more than 400,000 people across the globe. Within a week, that number had tripled. We have now surpassed 5 million cases worldwide.

It’s like population growth – if every person had 2.5 children (so every couple had 5 children), the population would boom. To prevent this you could insitute a one* child policy, like China did in the 1970s – if every couple has only one kid, population growth will decrease. This is what countries are trying to achieve for COVID-19.

Natural trajectory of COVID-19 (via Tomas Pueyo)

If we allowed COVID-19 to progress unabated, health services would be overwhelmed in no time at all and many people would die for lack of medical attention. Around 5% of COVID-19 cases need intensive care. If there are 4.9 million people in your country, even if only 5% of them get infected that’s 12,250 people who will need ICU beds. If, like Ireland, you only have around 250 ICU beds, they will fill up very quickly and pretty much everyone else who needs critical care will die. Not only the 12,000 excess people with COVID-19 but the people having heart attacks or strokes, the people with complications of cancer, exacerbations of asthma, emphysema or heart failure. People will die in their own front gardens waiting for ambulances, in EDs before a nurse or doctor ever gets a chance to see them and on chairs in hospitals because there’s nowhere else for them to go. Healthcare workers, constantly exposed to the virus, will get sick and die. Even in the best cases, they will be forced to quarantine for 14 days, leaving their already-overworked colleagues to pick up the slack (see Cavan General Hospital and the Mater in Dublin).

The red line is the number of ICU beds. The other lines are the number of people who need ICU beds (depending on different social distancing strategies) and are likely to die without them (via Tomas Pueyo).

Needless to say, we have to prevent this from happening. When it comes to prevention strategies, you have three options: containment, mitigation or suppression. For most countries, it’s far too late to use containment as the initial policy.


  1. Containment
    • Limit people entering the country
    • Identify the sick and immediately isolate them, perform diligent contact tracing and quarantining
    • Ensure all healthcare workers who interact with infected patients have adequate PPE
    • Used in Taiwan, South Korea, Singapore, and Hong Kong
    • Does not work if you have hundreds or thousands of cases in the community
  2. Mitigation
    • Quarantining, some social distancing, some isolation
    • Try to postpone infections so as not to overwhelm the healthcare system, and thus reduce mortality rate
    • Assumes that everyone who recovers from COVID-19 will be immune (untrue)
    • Assumes that SARS-CoV-2 doesn’t mutate (also possibly untrue)
    • Assumes that eventually a significant proportion of the population will be vaccinated (unclear and a vaccine won’t be available for at least 12-18 months)
    • Used in Sweden, and initially also the US, and the UK before a paper from Imperial College London made them see sense
  3. Suppression (the Hammer)
    • Quench the outbreak with stringent social distancing measures (close businesses, schools, public transport etc.)
    • Aim to lower transmission rate (R) from 2-3 to < 1 (less than one child policy)
    • Then release the measures, so people can gradually get back to something approaching normality
    • Cuts exponential growth of cases and mortality rate because the healthcare system isn’t completely overwhelmed
    • Buys time. This means:
      • Fewer total cases of COVID-19 and fewer COVID-19 deaths
      • Relief for the healthcare system and its humans
        • Build up capacity (buy equipment, PPE, ventilators)
        • Adequate training
        • Can learn more about COVID-19 and even find treatments
      • New testing methods (faster + cheaper – we could start testing everyone)
      • Ability to set up proper contact tracing
      • Public education (hand washing, cough hygiene, open doors with elbows, wipe surfaces)
      • Can get masks for everyone

Hubei locked down hard and within 7 weeks had only a trickle of new cases. This was the worst-affected region in China. The measures they took were stringent – only one person per household was allowed to leave home every three days to buy food, and their enforcement was severe. This severity likely stopped the epidemic faster. Had the US imposed social distancing measures a week earlier, they would have saved 36,000 lives.

Graph Credit: Thomas Pueyo

[You can play with different social distancing timings on the Epidemic Calculator and see how to screw over virtual populations by delaying it.]



VI – The Dance

Once suppression (‘the Hammer’) is in place and the outbreak controlled, the second phase begins: the Dance of R.

  • R > 1: infections grow exponentially
  • R < 1: infections die down

Transmission Rates During COVID StagesIn the early stages of infection you don’t have any symptoms, so you go about your normal business and in so doing, spread the virus to 2.5 people – by touching door handles / pedestrian crossing buttons, handling money, sitting beside someone on a bus, shaking hands, singing etc. Once you have symptoms you’ll stay home more or maybe even wear a mask. The worse your symptoms, the more isolated you become – by the time you’re sick enough to be in hospital, you’ll essentially stop spreading the virus because you’ll be contained.

When R >> 1 (on average people are transmitting the disease to >> 1 other person), we need to lower it. We lower it by reducing the number of people an infected person interacts with. Since 50% of infected people don’t know they’re infected, we have to use general measures that affect everyoneban events with more than a certain number of people, ask people to stay home where possible etc.

Depending on R (or the number of ICU beds available), we will either have to tighten up social distancing or be able to relax it (increase the 2km-from-home limit to 5km, allow groups of 4 people to meet outdoors etc.). This is The Dance (of R): a tango between getting back to normality, and between spreading the disease (all the while trying to quash the complacency that sets in for the un- or minimally affected).


HammerDanceA combination of comprehensive testing, isolation, rigorous contact tracing, and quarantining might enable us to loosen restrictions without getting overrun by the virus:

  • Widespread testing* could identify cases before they have any symptoms and isolate infected people, reducing their infectiousness
  • Contact tracing figures out who infected people have been in contact with and quarantining these contacts prevents them from infecting other people

If we don’t test enough (measured by having a 3% positive rate), we can’t isolate the infected, so we don’t know where they are, and are forced to apply a general lockdown (this is Ireland’s current state of affairs).

ReopeningWorking out what businesses to reopen and when is not an exact science but there are cogent arguments for reopening schools early on: current data suggests that children are half as likely to catch COVID-19, are at an unbelievably low risk of dying from it, have significantly lower viral loads, don’t spread it to adults very much, and suffer harm from lockdown. Children are not super-spreaders. The main reason to keep children at home is to protect adults.

EconoschoolsWe do need to watch out for super-spreading events. Transmission rates vary between people infected with COVID-19, with some people shedding far more virus than others. These people may exhale many more particles by talking louder or singing (loud indoor places like choir practices, nightclubs and Zumba classes have all been locations for outbreaks), or spread more droplets by not washing their hands. If such people go to a “high risk” setting (churches, rock concerts, fish factories, meatpacking plants, pool party) while they are highly infectious, it may set off a superspreading event – patient 31 in South Korea was at one point responsible for 60% of her country’s COVID-19 instances (now down to 40%) by causing over 5,000 cases. Where possible, try not to invite these super-spreaders over for karaoke.

SK31What about the psychological effects of quarantine?
These are (unsurprisingly) almost universally negative. People who are quarantined are more likely to exhibit symptoms of exhaustion, detachment from others, irritability, insomnia, and have difficulty concentrating. Some may suffer long term psychological consequences like PTSD symptoms or alcohol abuse, especially those quarantined for more than 10 days. Stressors include: longer quarantine duration, infection fears, frustration, boredom, inadequate supplies, inadequate information, financial loss, and stigma. The effects can be somewhat mitigated by having adequate supplies, clear communication regarding quarantine duration, warning signs etc. and having ways to communicate and socialise from a distance. Even in the absence of symptoms, it is greatly important to look after your psychological well being in these uncertain times.


Some psychological tips for improving your mental health during COVID-19 can be found here.


VII – Treatments and Vaccines

Treatments for COVID-19 would reduce the need for social distancing by shortening the period of infectiousness as well as the proportion of people who need intensive care. There are many proposed remedies – remdesivir, dialysis, chloroquine, hydroxychloroquine, ivermectin, bleach and others – and also many ongoing trials:

COVID TrialsThere are numerous calls for this research to be better organised and some movement in this direction. Most studies to date are so flawed as to have been useless – the NEJM remdesivir study had a serious statistical error, the result of which was to overestimate clinical improvement. The Lancet remdesivir trial showed no difference in mortality, with “improvement” differences so all over the place as to be largely uninterpretable. The best advice at the moment is to be highly cynical and to await results / messaging from trusted pharmaceutical bodies.

RemdTweetA vaccine would accelerate herd immunity and reduce the length of the pandemic, but a vaccine being available in 12-18 months is very much a best-case scenario. The last ten licensed human vaccines took seven years to develop.

In the absence of widespread testing, enforced isolation, rigorous contact tracing, obligatory quarantining, suitable treatments or globally available vaccines, a period of (sustained or intermittent) social distancing is unavoidable. One paper suggests that some form of social distancing might be required until 2022 and we certainly won’t be going to music festivals or large sporting events any time soon, never mind international travel.

“Even a perfect response won’t end the pandemic. As long as the virus persists somewhere, there’s a chance that one infected traveler will reignite fresh sparks in countries that have already extinguished their fires.”
– Ed Yong, The Atlantic


VIII – Masks

Viruses are spread via close contact with body fluids: mucous, blood, urine, and faeces. Most of us do a reasonable job of avoiding the latter three on our own, so when we talk about trying to reduce the transmission rate, we usually* just focus on mucous. Infective mucous is spread in three main ways:

  • Droplet Transmission
    • Someone with COVID-19 coughs or sneezes and shoots large droplets out of their nose and mouth
    • Anyone within 2m* (maybe even 8m) is at risk of these droplets coming into contact with their eyes, nose, or mouth
  • Airborne Transmission
  • Contact Transmission
    • Someone with COVID-19 coughs and large droplets settle on nearby surfaces (depending on the type of surface, the virus may persist for four days)
    • Someone else touches this surface and then touches their eyes, nose, or mouth

We can all decide how often we want to clean our homes, touch public surfaces, wash or sanitize our hands, or caress our faces* (maybe), and it’s easy enough to stay more than 2m* away from a person who is actively coughing or sneezing, but the fact that somebody could saunter by, clear their throat, and 20 minutes later you could walk through and inhale an invisible cloud of coronavirus particles does add a certain frisson to those supermarket trips.

Linsey Marr studies the transmission of airborne diseases and points out “People envision these clouds of viruses roaming through the streets coming after them, but the risk of infection is higher the closer you are to the source*. Outside is great as long as you’re not in a crowded park… When I go out now, I imagine that everyone is smoking, and I pick my path to get the least exposure to that smoke.

Simulation showing microdroplets 20 minutes after the man on the very right of the screen sneezes.

Places like lifts pose the highest risk, because they are enclosed spaces with limited airflow. When a window is opened, microdroplets are quickly swept away in the breeze – any airflow seems to get rid of the super-light particles. Scientists in Wuhan took air samples from public outdoor areas and showed that the virus was either undetectable or present in extremely low concentrations.

Graph COVID TransmissionAn often overlooked fact is that wearing a mask is not about protecting the wearer from infection, but about protecting other people. Wearing a mask prevents sick people from infecting others by keeping their droplets inside their masks. Even a cotton mask reduces the number of virus particles emitted. Spreading fewer particles means that other people have a better chance of avoiding infection, and if they are infected, the lower viral load they are exposed to gives them a better chance of having a mild illness.

50% of COVID-19 infections are spread by people who don’t have any symptoms (45% of them before they develop symptoms and 5% who remain entirely asymptomatic), so compelling sick people to wear masks only solves half of the problem (likely even less, given the tendency of symptomatic people to stay home more). We need healthy people to wear masks if we want to make any real difference to transmission rates.

Masks2Models show that 60% of people wearing masks that are 60% effective could, by itself, stop the epidemic. Mask use together with other measures (social distancing, contact tracing, quarantining etc.) is even more powerful – in Hong Kong, only four confirmed COVID-19 deaths have been recorded since the beginning of the pandemic. The health authorities credit near-universal (almost 100%) mask-wearing as a key factor.

Czechia and Slovakia were the first European countries to mandate wearing masks in public and have some of the best COVID-19 trajectories in Europe. Czechia went from 0% to 100% mask-wearing in public in 3 days.
[Note: Not everybody agrees with this – some argue that when people unused to masks wear them, they fiddle with the mask and are more likely to touch their faces.]

In the absence of medicines or a vaccine, masks are the only protection we can buy, and face masks have now been elevated into fetishised commodities. Luckily it’s easy to make your own (in as little as 40 seconds and even from a sock) but it’s important to learn how to put it on and take it off properly, to avoid contamination.

WP DIY Masks
Graphic via The Washington Post [Homemade mask manual here]
The fabric you use should be as dense as possible. As a rule of thumb, the less light a fabric lets through, the better but you need to be able to breathe comfortably through your nose and your mouth – if the mask is too thick / not breathable enough, you will breathe around the sides of it or take it off altogether (in which case it won’t work).

DIY Masks
A group of Cambridge University researchers compared filtration and breathability of different types of homemade mask materials, and concluded that masks made from pillowcases or a cotton T-shirts struck the best balance.

Some people, unable to purchase masks, are getting pretty inventive:



IX – How is Ireland Doing?

COVID DeathsIt depends who you compare us to (note: Ireland is one of the very few European countries that includes both nursing homes and suspected or probable COVID-19 cases in official numbers).

We’re doing better than England.
COVID Europe
We’re middling for Europe (Financial Times)
Nowhere near as good as New Zealand
…or Taiwan or Senegal.
Generally middling internationally.
We still aren’t doing enough tests.
COVID Lives Lost
We have lost all of these people.

Ní bheidh a leithéidí arís ann.


X – COVID-19 Worldwide

HumAid75% of humanitarian operations are currently on hold.

The UN-led $6.6 billion appeal to help 63 vulnerable countries through COVID-19 is only 15% funded as other nations concentrate on their own economies.

UNICEF estimates 1,200,000 children under five could die in the next six months due to the impact of COVID-19.

Photo Credit: Frank Dejongh

Take Home Points:

Wash Your Hands with Soap

Wear a Mask

Keep More Than 2m Away from Other People

Stay Informed

Every COVID-19 Death Represents a Full and Cherished Human Life

Spare a Thought for Those Less Fortunate and Do Something to Help, If You Can



See Also:

One thought on “COVID-19 AMA

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