How masks work

Mombasa residents at the Likoni crossing channel on April 2, 2020. PHOTO | KEVIN ODIT | NATION MEDIA GROUP

What you need to know:

  • Dr Joshua Santarpia, who studies biological aerosols at the University of Nebraska Medical Center in the United States, found out that when a person stands by the bed of a patient, it does not matter whether the patient is speaking or not.
  • The particles the patient emits as they breathe would be inhaled in by someone that is a metre and a half away from them – at the foot of bed.
  • Should these particles be pathogenic, containing the virus causing the Covid-19, Sars-CoV-2, the healthcare provider would be infected.

The world is united on the need to suppress the novel coronavirus Covid-19, but the jury is still out on two things: whether the disease is airborne and if the public should wear face masks, like healthcare workers.

The confusion stems from the position that the World Health Organization (WHO) has taken on both issues, yet one affects the other: masks reduce the spread of respiratory infections.

The WHO’s technical guidance on how Covid-19 is transmitted states that Covid-19 is primarily transmitted through droplets from and close contact with infected individuals”. For this, it prioritises regular hand washing and cough hygiene as means of protection.

The WHO directs that protections against airborne transmission are especially important for healthcare workers when they do medical procedures that might be anticipated to produce smaller respiratory droplets that could then be inhaled. This includes insertion of tubes in patients, an act that was performed by some registrars and medical officers.

Some evidence supports this theory but also adds another mode of transmission, especially in healthcare settings.

Dr Joshua Santarpia, who studies biological aerosols at the University of Nebraska Medical Center in the United States, found out that when a person stands by the bed of a patient, it does not matter whether the patient is speaking or not.

The particles the patient emits as they breathe would be inhaled in by someone that is a metre and a half away from them – at the foot of bed.

Should these particles be pathogenic, containing the virus causing the Covid-19, Sars-CoV-2, the healthcare provider would be infected.

The National Academies of Sciences, Engineering, and Medicine which is often called upon to advise the United States government, cited Dr Santarpia’s evidence and wrote in a letter to the American White House Office of Science and Technology.

"Currently available research supports the possibility that SARS-CoV-2 could be spread via bioaerosols generated directly by patients' exhalation," read the letter.

Bioaerosols are the fine particles let out when someone breathes and that can be suspended in the air, rather than larger droplets produced through coughs and sneezes.

“Any time someone who has a disease that has affected the lungs, there is a possibility that when they speak, sneeze or cough, they will release large and small droplets in the air,” said Dr Jeremiah Chakaya, a pulmonary diseases expert.

It is these bioaerosols and droplets that the masks prevent from getting to you.

The Centers for Disease Control and Prevention (CDC) also warns that as many as 25 percent of people infected with the Covid-19 may not show symptoms and this is why the CDC has broadened its guidelines on who should wear masks.

The prophylactic use of masks dates back to the 1918 influenza pandemic – the H1N1 virus that came from birds and that is infamously known as the Spanish flu – that is estimated to have infected about 500 million people, or one third of the world’s population at the time. It was airborne and it killed more than 50 million people.

In the modern day, there are N95 masks and respirators. The masks draw their name from their ability to filter out 95 percent of nearly all of bacteria, viruses, fungi and other microbes, even in their tiniest form.

This is how these masks work. The N95 is made up of a thick mesh of plastic fibres that trap the disease-causing germs on the inside (for the person who is sick and does not want to release this to the environment).

The surgical masks are the more popular ones. They are soft with pleated lines and they have a string that can be put on ear loops or tugged under the chin. But this comfort makes them more loose and this allows more air to leak through the sides.

They are also able to protect the healthy person on the outside as they trap the microbes that are already in the environment so that they do not inhale them.

Now, due to the global shortage of masks and other personal protective equipment, the CDC advises that scarfs and do-it-yourself masks will serve the purpose.

However, not all fabrics will serve the purpose. Dr Yang Wang, an assistant professor of environmental engineering at Missouri University of Science and Technology, said the fabrics for homemade face masks need to be “efficient for removing particles, but you also need to breathe”.

Dr Wang’s research reported that four layers of fabric offered more protection than just two layers. A 600-thread count pillowcase, her study stated, captured 60 percent of particles, compared to just 22 percent of particles when doubled. A thick woolen yarn with four layers filtered 48.8 percent in four layers.

N95 or not, there is a proper way to wear and dispose of the masks. Kenyatta National Hospital surgeon Elly Nyaim warns the wearer not to touch the outer front part of the masks.

“If it had trapped any pathogen there, then you touch it and then touch your face or clothes and contaminate yourself,” said Dr Nyaim.

So when you wear a mask, position it over your mouth and nose. Then fasten ties or tapes above and below your ears at the back of the head.

Do not touch the front part of the mask throughout the day. When it gets wet or at the end of the day, untie or break the ties at back of head.

Ensure that your hands are clean as you do so.

Remove the mask by only handling it at the ties. Discard it in appropriate waste and then wash your hands with soap and running water.