Blog: Health Matters

(The contributors to this article:  Tharien van Eck (MBChB), Heather Davis (PhD) and Martha Canning (PhD)) 

The Target Team is aware of the vast amount of conflicting information circulating at the moment regarding hygiene and COVID-19, and knowing that we all want to protect ourselves, our loved ones and communities, we felt that it would be good to update you with information on how to do so. 

To start, it is helpful to understand the differences between bacteria and viruses.

1. Bacteria are living cells that can divide and make more copies of themselves; they can do this in tissue, skin, blood, etc.; it isn’t necessary for them to be inside a human cell to divide. Bacteria can be killed by various means, most often antibiotic drugs. 
2. In contrast, viruses, such as SARS-CoV-2 that causes COVID-19 disease, are not living cells, but rather a piece of genetic material (RNA in this case) covered by a protective “envelope,” which is a layer consisting of proteins and lipids (fats). A virus cannot divide and make more copies of itself on its own – it needs to get inside a cell of the infected host, as it uses the cell’s machinery to make more copies of itself. These copies are released from the cell and can then go and infect additional cells.

Since the virus is not a living cell, in a literal sense it can’t be “killed,” but it can be destroyed. Outside the body, where it has no cells to infect and propagate itself, it will eventually disintegrate by itself. The speed of disintegration depends on temperature, humidity, the type of material on which it rests and other agents it is exposed to.

How do infected people spread viruses? How do we reduce the risk of transmission?

It is very important to recognize that infected people can spread a virus during the asymptomatic incubation stage, which can last up to 2 weeks (or 4 weeks in rare circumstances); some people will never develop symptoms, yet can spread the virus for a number of days. Recent data suggests that 25-45% of all infections are spread by pre- or asymptomatic people. It is for this reason that we all need to behave as if everyone, including ourselves, could be infected.

There are three main ways that an infected person spreads a virus: 

1. Inhalation of large respiratory droplets (5-1000 μm) is believed to be the primary method of spreading infection. These larger droplets are heavier, so they will not travel far before gravity pulls them down onto surfaces. These can be inhaled if you are in close contact with an infected person, but are more likely to settle on surfaces, which can lead to contact transmission when another person touches those surfaces. The social distance guidance to stay apart by at least 1.5 or 2 meters is intended to reduce the risk of inhaling large respiratory droplets. Wearing a mask when social distancing can’t be respected reduces the risk of transmission by large respiratory droplets.
2. Inhalation of smaller aerosols (<5 μm) is also thought to be possible with this virus. It is estimated that one minute of loud speaking could generate more than 1000 virus-containing aerosols (V Stadnytski et al., PNAS, 2020). If aerosols are proven to be a possible mode of transmission, this does present several concerns. First, aerosols don’t settle quickly and can float in the air for several hours, and this means (i) virus aerosols can still be in the air after the infected person moves away, (ii) the aerosols can travel much greater distances than 2 meters by breezes or air currents (e.g., air conditioning), and (iii) the density can build up over time in an enclosed space (car, plane, small room). Second, inhaling small aerosols carries the virus much deeper into the lungs, bypassing the main immune protective tissues in the nose and throat, and thus may result in a more severe disease outcome. One way to think about it is, if you are close enough to a smoker to smell cigarette smoke, or to a woman to smell her perfume, then you are close enough to be exposed to aerosols. For the reasons described above, the social distance guidance is less effective against small aerosols, especially inside buildings where the density of the virus is less likely to be diluted into a large volume of air.
3. Contact transmission through touching a virus-contaminated surface. The most direct route would be to shake hands with an infected person who has covered a cough with their hand. Although few are shaking hands anymore, other surfaces can be contaminated with virus by an infected person touching them or by large respiratory droplets settling on them. If you touch a virus-contaminated surface, you can then infect yourself by putting your fingers in your nose or mouth, rubbing your eyes, or even just touching your face. This is the basis of the strong advice for frequent handwashing and use of alcohol gels when that isn’t possible. It should be accompanied by sterilizing mobile phones, credit cards, car keys, etc., if you may have touched them while your hands were contaminated. Mobile phones can be sterilized by rubbing with a cloth impregnated with rubbing alcohol (makeup remover pads work well).

Masks: Having everyone wear masks reduces but does not eliminate the risk of infection by respiratory droplets and aerosols, since they can pass through cloth masks to some extent, but it does reduce the risk, and many countries now recommend they be worn by everyone when social distancing can’t be respected. This advice has changed over the past months. The WHO originally did not recommend the use of masks except for those known to be infected, but this was based on learnings from SARS and did not account for key differences now known about SARS-CoV-2: namely, higher infectivity and asymptomatic spreading. The correct wearing and handling of masks between uses is important;  you should be very aware of touching the mask, try to handle the straps or ties of the mask only, and wash your hands after handling the mask.

More about the virus in the air 

The likelihood of getting infected by sharing air with an infected person depends on several factors:

• Viral load: some people put out much higher amounts of virus in their respiratory droplets than others; these people are sometimes referred to as super-spreaders. Being near a super-spreader is riskier than being near someone who sheds less virus.
• Size of droplet: large particles may carry more virus but settle more quickly and can be avoided with social distancing and masks. The smaller aerosols travel further, stay longer in the air and may be inhaled deeper into the lung, potentially causing a more serious infection.
• Space: this relates to viral density. The more limited the space, the higher the concentration of the virus and the greater likelihood of becoming infected. The more the space is open and ventilated, the more the concentration of the virus is reduced. Therefore, meeting people outside is less risky than indoors.
• Air currents: these can spread the virus particles further, as was evidenced by a woman who infected nine people in a Singapore restaurant – all five at her table, but also four at an adjacent table on the side where the air conditioner would blow her respiratory droplets or aerosols. On the other hand, air currents can also dilute the virus into a larger volume of air making it less infectious, especially when outside.

Virus on surfaces – how long does it last?

The most important factor for how long viable infectious virus lasts on a surface is the nature of the surface itself. A general rule of thumb for different surfaces:

• 3 hours on dust or another porous surface (fabric)
• 4 hours on copper (it is naturally antiseptic) 
• 4 hours on wood (which dries it and prevents it from coming off easily)
• 24 hours on cardboard
• 42 hours on a metal
• 72 hours on plastic

Other factors that can affect how long the virus remains infectious on surfaces:

• Temperature: While heat destroys the virus, cold preserves it. Therefore, the risk of infection is greater in air-conditioned environments (e.g., buildings, cars), and putting an infected item in the freezer will just preserve the virus until you take the item out (scientists keep viruses in freezers for years). 
• Moisture: Some moisture is required for a virus to remain stable.
• Light: Ultraviolet light (sunlight) can speed up viral decay by decomposing the protein of the envelope, regardless of the surface it is on. A UV lamp is a good way to disinfect a reusable mask.

Thus, a porous surface in a dry (dehumidified), warm and sunny environment is best. A shiny smooth surface in a cool, moist and dark environment is not so good. 

How to destroy the virus on surfaces?

• Soap or detergent: foam disrupts the lipid (fatty) envelope layer and the virus falls apart. The more foam the better, which is why the instructions are to vigorously rub your soapy hands for 20 seconds or more. It is also possible to clean solid surfaces with soapy solutions; make sure you create foam. 
• Heat melts the fatty layer; use water above 30° C for cleaning, washing clothings or anything else. In addition, hot water produces more foam, making it more efficient. Studies have shown that for hand washing, both cold and warm water are effective, as long as soap is used and the duration of hand washing is at least 20 seconds.
• Alcohol or any other mixture containing at least 60% alcohol (e.g., sanitizing hand gels) dissolves the outer lipid layer of the virus. Spirits such as gin or vodka are not effective, as the alcohol content is too low (<50%). Listerine has 65% alcohol, so it can be used (except the alcohol-free version).
• Bleach dissolves the protein component of the virus envelope. Use a mixture of 1 part bleach mixed with 5 parts of water. This will dissolve the protein immediately and destroy the virus.
• Hydrogen peroxide (100%) will also dissolve the protein component of the virus envelope, but if used you should wear gloves as this high concentration is harmful to the skin.

What doesn’t work?  Bactericides and antibiotics are useless as the virus is not a living cell. Vinegar has no effect.

Other advice:

Never shake clothes after wearing; if you shake a cloth or use a feather duster, the virus molecules can float in the air for 3 hours and sit in your nose.

The virus cannot pass through healthy, intact skin, so it is okay to have the virus on your hands, but make sure you wash them before you touch your face. However, by washing your hands a lot they may get dry and develop micro-abrasions where viruses can enter – so make sure you use a hand moisturizer to keep the skin healthy. A thick, glycerin-based moisturizer is best.

Always think about where your hands have been and what surfaces might be contaminated; then if there is a risk that your hands are contaminated, wash them before touching your face or anything in your home. Also keep your nails short to prevent viruses from being trapped under the nails and not washed away.

When will it be safe to stop COVID-19 hygiene habits?

The short answer is not until there is herd immunity, and for you as an individual, not until you yourself have protective antibodies, either because you were infected and recovered with adequate antibodies, or because you have been vaccinated.

Herd immunity:

Herd immunity means that a significant proportion of the population has protective immunity, so that the virus can no longer spread easily within the community and it fizzles out. The proportion of the population that needs to have protective immunity depends on the infectivity of the virus but is typically at least 50% of the population. For a highly infectious virus like measles, it needs to be closer to 95%. For COVID-19, it is estimated that 60-70% may be required for herd immunity.

Today, herd immunity is always achieved through vaccination, as this is the only safe way to ensure large proportions of the population are immune against a given disease. In theory, herd immunity could be achieved for COVID-19 through natural infection, but in practice it is an unacceptable approach. With Wave 1 of COVID-19 infections now past the peak in many countries, serology testing shows that only 2-5% of the population now have antibodies. This is a very far way from offering herd immunity and the idea of what would have to happen for more than 50% to have antibodies through natural infection is frankly unthinkable.

Vaccines – Let’s be realistic: 

Enormous efforts are underway to develop a vaccine against COVID-19. Development of a new vaccine occurs in several different stages to ensure that the vaccine is safe and effective. It typically takes 5 to 10 years, so the current efforts to develop it in 12-18 months are unprecedented, and while possible, are not guaranteed. Of the more than 100 vaccines currently under development, many will fail, but some should ultimately succeed. Here are some key points to keep in mind when you hear news about vaccine development for COVID-19:

• While success for at least some of the vaccines is likely, it isn’t guaranteed that a vaccine can be developed against COVID-19. To date, no one has succeeded in developing an effective vaccine against HIV, despite more than two decades of extensive effort.
• It is important that all steps of vaccine development are respected to ensure that the vaccine is safe and effective. Short cuts should not be permitted despite the urgent need. If the wrong type of immunity is induced, it can actually make the disease worse than if the person was never vaccinated. When a company says they have “developed a vaccine,” they can mean many different things. For those who announced it early, it means they have designed and constructed a molecule that could potentially be a vaccine. But this is very far from success, as they have many steps to take, and there is a significant risk of failure at every step. 

Expected outcomes if COVID-19 hygiene habits aren’t maintained: 

This pandemic is not over; it is just getting going. One myth to address immediately is the concept of a second wave that won’t come until November. That is influenza they are talking about – not COVID-19. Influenza is a seasonal virus and starts around November of each year in the Northern Hemisphere. It is not known that COVID-19 is seasonal; plenty of viruses are not. The fact that it spread quite effectively in Australia during its summer, as well as in other hot countries (Singapore, Middle East) suggests that there may be no seasonality.

Many societies are starting to open up, not because it is completely safe to do so, but because there are competing needs to keep people safe from the virus: for example, the economy, mental health, employment and avoiding starvation. As an individual, you should realize that if your government removes restrictions, it doesn’t mean they can guarantee your safety from getting infected. No, it means they have enough empty hospital beds to be able to treat you if you get sick.

It is important to remember that this is a new virus, and new information based on clinical evidence, research and patient experiences accumulates daily. Many of the projections made are just that: projections. 

Some of this information will change, as we learn more about this new Coronavirus. So far, the most valuable information needed to protect yourself and others has been to practice social distancing, sneeze or cough into the inside of your elbow, avoid touching your face, wash your hands regularly (especially after touching surfaces in public) using running water and soap, for 20 seconds (sing the Happy Birthday song twice), use alcohol-based hand gel if hand washing facilities are not available, and follow the mask protocol where you live. Keep in mind that masks are most useful in protecting the public from an infected person – the trajectory of droplets and aerosols is broken by a mask, so that these do not go straight out into the air at full force. Avoid crowded places, and choose alternatives to public transportation if you can.

Maintain a healthy lifestyle, including exercise and a diet high in fruits and vegetables, and hydrate with water. Be cautious and considerate, but do not live in fear. And check up on your friends and neighbors – even with social distancing requirements, we still need each other!