Covid-19 Basics

by Dr Marlies Craig (PhD Epidemiology, Basel University)

Last updated: 13 July 2020


What do we know about Covid19?

Covid19 is a novel coronavirus. Novel means brand new.

Everything we know about it we have learned since December 2019. While the pandemic is spreading like wildfire, science is scrambling to catch up. It is a strange, complicated disease, and there is so much we do not know about it yet.

Governments have had to make tough decisions at a time when there was not a single paper or book written on the subject. The science we have now has been published in a rush to get at least some information out there. Some of it has already had to be retracted because it was published too quickly. We are learning even while responding to the crisis. That is like studying to be a doctor while carrying out surgery or learning to play an instrument while performing in a concert.

To make good decisions, we need to:

  1. have good information (solid scientific data, rather than anecdotes, hear-say or panic);
  2. believe the numbers (instead of denying them);
  3. act on the conclusions (instead of doing things that contradict the conclusions or doing nothing at all).

This is true for governments, as well as for individuals. Whatever information is out there, we need to inform ourselves, be willing to learn.

Then we need to be willing to change our ways, to act on what we have learned, to do the right thing. We expect this of others, we expect this of the government. Others expect it of us too.

As humans we also need to be willing to help each other. This is not the time to be selfish, this is the time to come together, to be loving, kind, generous, compassionate, and considerate.

This booklet is an attempt to summarize some of the important things we have learned about Covid19 so far. Remember, a lot of this information is still new and uncertain, and we learn more every day.

How bad is Covid19?

  • Covid19 is a brand new virus.
    • Humanity has never been exposed to it before, so there is no immunity.
    • We have no medicines to cure the virus, no vaccines to prevent it.
    • At first, we didn’t even have diagnostic tests to test for it. The tests we have now were made in a rush and are not totally reliable yet.
    • There is no established literature on this virus yet. The science on this virus is new and largely untested.
  • Covid19 is often deadly, as deadly as some ‘dread diseases’.
  • Covid19 is most dangerous for old people. Number of deaths per confirmed cases are highest for older age groups:
  • Covid19 is most dangerous for people with some other health issues such as those in the graph below:
  • Covid19 spreads fast: confirmed cases have gone up from 1000 to 1 million in just over two months, and to 10 million in another three.
  • Covid19 is more deadly than many other diseases. For example:
    • By late June 2020, 500 000 people have died of Covid19, that is 2% (1% for age 50, up to 15% for age 80 and older).
    • Each year, probably up to 1 billion people catch the flu, though not everyone gets sick. Flu has a death rate of about 0.1%. Covid19 has killed more people in the past 3 months, than the flu does in a year.
    • In one year (2017) about 219 million people caught malaria worldwide, and 435 000 died, that is a death rate of 0.2%. Covid19 is 10 times deadlier than malaria.
    • Tuberculosis (TB) is currently the number one infectious disease in the world; it kills more people every year than any other. In 2018, 10 million additional people contracted TB and 1.5 million died. Starting from zero, Covid19 has already infected 10 million in just half a year and is already a third of the way in terms of deaths.
    • The number of people who die within 5 years of being diagnosed with prostate cancer is 1.4%, 8.3% for melanoma; and 10% for breast cancer (1% if it is caught early). Compare that with Covid19 death rates of 1% in 50-year olds, up to 15% in 80+ year olds. Depending on age, Covid19 is like catching one of these cancers while shopping and passing it on to your family a few days later.
  • Covid19 is not at all like getting the flu. In China it was like this:
    • 81% of confirmed cases did not need to go to hospital. This so-called ‘mild’ disease is defined as ‘non-pneumonia or mild pneumonia’.
    • 19% of cases required hospitalization.
    • 14% of total cases were ‘severe’: acute respiratory distress syndrome, with rapid, shallow breathing, rapid heartbeat, lowered blood pressure, need oxygen.
    • 5% were ‘critical’: respiratory failure, septic shock, multiple organ dysfunction or failure, need ventilator.
  • Symptoms typically last for 1 to 2 weeks but can last much longer.
  • Roughly 2% of confirmed cases have died so far world-wide.
  • Covid19 is classed as a ‘Severe Acute Respiratory Disease’ (SARS), but there are more and more worrying reports about how the virus attacks not only the lungs, but also other organs: the brain and nerves, heart, kidney, liver, blood, testicles, etc.
    • It is possible that the virus can cause long-term or even permanent organ damage. There are also more and more cases of people who do not seem to get better, the virus keeps coming back, in waves. Some people are unable to go back to their normal lives. All this is very concerning.

These facts and findings are listed here not to sow fear, but to convince anyone who does not realise it yet: Covid19 is truly a very serious disease. Any actions or precautions, including lockdown imposed by government, is by no means an over-reaction.

What are the symptoms of Covid19?

The most common symptoms seem to be: fever (frequent but not always present), (dry) cough, frequently loss of smell or taste, eye complaints (watery, sore, light-sensitive), fatigue, chest pains, chills, sore throat, coughing up sputum, shortness of breath.

Less common symptoms include muscle aches, diarrhoea, nausea, loss of appetite, panting, headache, confusion, joint pains, dizziness, disturbed consciousness, abdominal pain.

How does it spread?

  • Covid19 spreads in tiny droplets of moisture, which we breathe out when we cough, sneeze, shout, sing, talk, or even just breathe. It does not require direct contact between people.
    • Bigger droplets soon fall to the ground or onto surfaces. We can get infected when we touch these surfaces, and then touch our faces. We all touch our faces very often – usually several times per minute.
    • It looks like the virus can survive on surfaces for several hours, up to 3 days.
    • Smaller droplets can drift in the air for a while. 
  • Epidemics spread through a population, by infecting one individual after another.
    • The more contact someone has with others, the more likely they are to pass on the virus.
    • The more people meet or cross paths in one place, the higher the risk at that location.
    • Contact tracing is the attempt to locate everyone who could have come into contact with an infected person.
The more contact someone has with others, the more likely they are to pass on the virus.
  • Hotspots are locations where risk of infection is very high.
    • These are places where crowds come in close contact with each other, for extended periods of time, closed spaces with poor ventilation, such as conferences, worship meetings, choir rehearsals, clubs, bars, entertainment, funerals, fitness or dance classes, etc.
    • One study that carefully traced 318 local outbreaks involving three or more cases, found only a single outbreak that occurred outdoors, and it resulted in only two cases. All other transmission occurred indoors. Outbreaks often involved transmission in more than one venue. Transmission in the home environment was very common (this happened in 80% of local outbreaks), also during transport (34%). Other common venues were restaurants / food outlets, entertainment and shops.
    • In another study risk of infection was 19 times higher indoors than outdoors.
  • There are also ‘super-spreaders’: individuals who pass on the disease to sometimes hundreds of other people.
    • As few as 10 percent of infected people may cause 80 percent of transmission, in certain situations.
    • These can be people who are infected without knowing it, who do not follow the precautions, who move around indoor environments and mingle with many other people. They can be well-intentioned, chatty, and sociable people, who like to talk, hug and shake hands. This could be any one of us.
    • Remember: It is not the people who are the threat, but the virus.

How does Covid19 progress?

Humanity has never been exposed to this virus before, so our immune systems have no ‘code’ that could immediately mark and target the virus. The way our bodies respond, depends on how effectively our individual immune systems can recognize and fight off this new threat. The stronger and more active our immune system, the more powerful the counterattack.

We are seeing a wide range of responses, in terms of how sick people get, how long they take to get sick, how long they take to recover, or whether they develop any symptoms in the first place.

  • Incubation period: the time from infection to first symptoms, is usually around 4-6 days but can be anything from 2 to 14 days or even longer.
  • Infectious period: throughout this time the person is shedding viruses, able to infect others. Transmission can start several days before the first symptoms and can continue for a week after symptoms clear up.
  • Pre-symptomatic infectious period: This period, where people are infected and contagious, but do not yet feel sick, is the most dangerous for public health.
    • One study estimates that this period lasts on average nearly 4 days, and that from 20 to 80% of transmission can happen during this period – depending on how strictly cases are isolated after onset of symptoms.
    • Another study found the highest number of viruses in throat swabs (viral load) on or even before the onset of symptoms. We may well be most infectious before we feel sick, or just as we start experiencing the first symptoms.
  • Asymptomatic infection: some people may become infected but never end up getting sick at all. There is now evidence that people with no symptoms have similar amounts of virus in their throats, and can transmit the infection nearly as easily, as people who do have symptoms. So people can get infected, never feel sick, never know they have the virus, and still pass the virus on to others.

Is there any good news?

  • Covid19 can be avoided or prevented.
  • Covid19 affects children much less than adults.
  • Covid19 is not spread by mosquitoes, and very likely not by pets.
  • Individual Covid19 viruses do not blow around freely in the air. They only travel in droplets, as described above.
  • Infectious droplets dissipate quickly outdoors. Transmission happens mostly indoors.
  • The virus breaks down when exposed to soap or alcohol.
  • It is possible, through meticulous self-isolation, to stop the virus spreading even to other people in the same household.
  • Work on treatments and vaccines is progressing rapidly.

This virus can be defeated. Some countries have proved it. There is no reason to lose hope, but every reason to be extremely cautious!

How can one prevent Covid19?


A mask catches most of the bigger droplets as we breathe out. It should be made of three layers of fine weave fabric and must always cover both nose and mouth. Always take off a mask by the strings and wash it directly.

Cloth and surgical masks can shield us from splutters and bigger droplets produced by others, but not from breathing in fine mist. Only special N95 masks filter out small particles.

A mask is also protective because it can stop us touching our faces after touching contaminated surfaces, and so infecting ourselves. But it works only if we do not fiddle with the mask and touch our faces anyway.

Washing hands with soap (hand sanitizers)

The human skin is a humid, oily, uneven surface, probably a good place for the virus to survive. Soap kills the virus because it destroys the viral skin (the fatty envelope that keeps the virus together). It also dissolves the oil that glues the virus to our skin, so the virus can wash off easily.

Alcohol-based hand-sanitizer also kills the virus, but to get the same effect as soapy water, hands must be covered in alcohol completely. A little whiff is not enough. When we are out and about, a hand sanitizer may be the only option, but nothing beats washing our hands with normal soap.


Keeping a distance of at least 2 meters when talking to someone, protects against the larger droplets that contain the largest number of viruses, and puts more distance between us to allow those tiny air-borne droplets to blow away.

Avoid large, crowded, gatherings at indoor venues with poor ventilation. Meet other people outside whenever possible, a few at a time. It also helps to keep the duration of interactions short. The longer we mingle, the greater the chance of transmission.

Also, as far as possible, avoid hotspots of transmission: places where many people mingle or cross paths, or take extra special care when you cannot avoid them (e.g. shops, public transport).

Surface cleaning

A study showed that viruses can survive on paper and copper for a few hours, on cardboard for 1 day, wood and cloth for 2 days, stainless steel and plastic for 3 days, glass and money for 4 days.

Surfaces can be decontaminated with an antiseptic made from 60-70% ethanol; or 50–100% isopropanol; or 0.1% bleach; or 0.5% hydrogen peroxide; or 0.2–7.5% iodine. Note: not every sanitizer works!

Groceries can be decontaminated by leaving them to stand untouched for a few days. Perishables in sealed packets or containers, also fruit and vegetables that were sold loose and handled individually at the shop, can be washed in soapy water and rinsed. Prepacked food can be transferred to a clean packet or container, and the packaging discarded.

Note: freezing or refrigerating does not destroy the virus and may even preserve it.


The current recommendation is that people with Covid19 symptoms who are ‘under investigation’, should get tested and self-isolate until they get their test results.

People who are ‘close contacts’ of a confirmed positive case, must quarantine for 14 days. If they develop any Covid19 symptoms, they should get tested. If the test is negative, ‘close contacts’ of a confirmed case still need to complete the 14 days of quarantine. If they test positive, they will need to go into isolation.

It may be a good idea to pair up with a friend and agree to help each other out (with shopping and food for instance), in case one falls ill.

Why lockdown?

The number one priority for the government is to protect its people from deadly threats. The purpose of lockdown, or ‘sheltering’ as it is also called elsewhere, is to slow down the spread of the epidemic and ‘flatten the curve’.

That means slowing down the spread of the virus, so that the number of severely ill patients who need hospital care, is never greater than the number of hospital beds (and staff) available. When you start running out of hospital beds, or hospital staff, that is when things get really bad, because people who need life-saving care, cannot get it.

These safety procedures only work if the majority of people participate. The more people refuse to follow the guidelines, the more bitterly everyone will regret it later. The more carefully we observe all these precautions, and the more people comply, the safer everyone will be, and the more we will all together slow down the spread of Covid19.

Hopefully, science will soon develop medicines and vaccines, as well as better, cheaper, rapid tests for quick diagnosis. But for now, the only way to slow down the spread of Covid19 is through diligent behaviour changes.

Ubuntu in this Covid19 pandemic means, I do it for you, and you do it for me. We all take precautions to protect and care fo each other.


  • Infectious disease: a disease caused by being invaded by a virus, bacterium, fungus or parasite
  • Transmission: when the infection passes from one person to another
  • Confirmed case: someone who has been tested and found to have the disease
  • Disease outbreak: when the infection spreads over a relatively small area, infecting a relatively small number of people
  • Epidemic: a large outbreak of the disease, so it spreads through a large population, resulting in many cases
  • Pandemic: a serious epidemic that spreads very far and wide over many regions of the world, and with very many people infected
  • Reproductive rate (R0): the average number of people that each infected person passes the disease on to  
  • Flattening the curve: slowing down the spread of the disease
  • Contact tracing: attempting to locate all people who might have had contact with an infected person


Once you have read the booklet, we would appreciate your feedback.

Acknowledgements: Sincere thanks to the following people who reviewed this document: Dr Fathima Suleman, Dr Nina and Garth Hunter, Anwen Cunningham, Egon Volker, Gisela and Martin Tscheuschner.

Originally compiled for Altersheim Port Natal retirement home, South Africa.

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