We all hope to lead a healthy lifestyle, one that does not include sickness or battling diseases. We take good health for granted until we learn how precious it is when we fall ill. We have a worldwide pandemic that we are currently facing and staying alive each passing day has become the new greatest accomplishment of the human race. Simply existing has never become so valuable. As such, it is important that we learn the basic science of disease transmission.

Many diseases can be spread via respiratory droplets that are propelled into the air by sneezing and coughing. The aerosols generated by coughing and sneezing contain droplets of moisture of varying size that are contaminated with infectious agents. Droplets can be propelled up to 6 to 12ft depending on the size of the droplets and the force of expulsion.

Types of droplets

The largest droplets are more likely to fall to the floor or ground fairly rapidly. Medium sized droplets are more likely to enter the nasopharynx of someone nearby, and can stick to the cells lining the nasopharynx where they can cause infection. Moisture in the smallest particles tends to evaporate rapidly, resulting in the formation of droplet nuclei, which are very light and can remain airborne for some time. Droplet nuclei can travel from room to room or through ventilation ducts. They can also travel around the edges of standard paper masks that are typically used during surgery or other medical procedures. Because of their small size and light weight, their movement is dictated by air currents, and, if inhaled, they can flow with inhaled air far down the respiratory tract, possibly reaching the alveoli.

Diseases caused by the droplets

As a result, inhaling large or medium sized droplets tends to cause upper respiratory tract infections, while inhaling the smallest particles (droplet nuclei) can cause pneumonia. Diseases that are typically spread by inhalation of medium sized droplets include 1) bacteria for example Neisseria meningitidis – a cause of bacterial meningitis and Streptococcus and 2) viruses for example many viruses causing the common cold, laryngitis, tracheitis, influenza viruses. In contrast, tuberculosis (caused by the bacterium Mycobacterium tuberculosis is spread by droplet nuclei. Scientists have gone back and forth but it has been established that the corona virus can be both airborne and spread through droplet transmission.

An individual within 1meter of someone infected with corona virus is therefore at risk of having their mouth, nose or eyes exposed to infective respiratory droplets. Respiratory droplets can also contaminate inanimate objects through coughing or sneezing or by transmission from hands contaminated with a sneeze or a cough. A susceptible individual can therefore acquire disease by inhalation of airborne particles. Alternatively, one can become infected by touching the person or inanimate object that is contaminated and then rubbing one’s eyes or allowing the infectious particles to enter the nose or mouth.

With this basic information on transmission of diseases that are airborne, it is needless to say that hand washing and respiratory hygiene provide a simple way of limiting this mode of spread. Constant sanitizing is crucial, especially now facing the corona virus. Social distancing, wearing recommended masks, constantly washing our hands and exercising our due diligence on limiting the spread of the virus are among the most important things expected of us right now. And to you reading, I am glad you are Alive!

By Wanjiru Muhoro | Writer

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