Updated: Apr 21, 2020
The Spread of Infection
Have you ever taken a public transportation bus or train and notice someone cough? Sometimes a person close to them coughs too, then another person coughs on the train and slowly the coughing makes it way closer to you. A situation like this would cause people to leave the train cart or exit the bus in the current climate. However, this is a fairly common occurrence. Ideally, we would like to think that people who are sick would stay home or at lease cover their mouth, unfortunately, this is not the case. The Centers for Disease Control states that from 2017 to 2018 45 million people became infected with influenza (the common flu) and over 60,000 people died in the united states alone. Seasonal Influenza has an R0 (R - naught) of 2 to 3, and the Coronavirus is thought to have an R0 of 1.4 to 4.08.
Understanding the Importance of the R0
R0 (pronounced R-Naught) is a technique epidemiologist, people who study the spread of disease, use assess how quickly a disease can spread in a population. The valve of the R0 relates to how many healthy people an infected person is likely to infect. If the R0 of an infectious disease is less than 1 then the infectious virus or bacteria will die out due to lack of hosts. If the R0 is at or around 1 then the virus or bacteria will continue to live and infect other people however, not cause a large outbreak. If the R0 of an infectious disease is more than one then it has the potential to cause a large outbreak.
Applying The R0 Knowledge
The R0 of the seasonal Influenza Virus is 2 to 3. This means that a single person infected on average has the potential to infect 2 to 3 other people. Each one of those newly infected also has the potential to 2 to 3 other people and this continues. The R0 of the seasonal flu resulted in over 40 million people becoming infected with this virus. However, the public is familiar with influenza and there is usually not panic during flu season, just extra necessary precaution.
Joseph Eisenberg in his 2020 article " How Scientists Quantify the Intensity of an Outbreak Like Coronavirus and Its Pandemic Potential" wrote that the suspected R0 of the coronavirus (CoVID-19) is thought to be between 1.4 to 4.08. Information on the coronavirus is still coming out and at the moment the majority of the new is simply speculation. COVID-19 has the potential to be less infectious than the seasonal flu, however, precautions should still be taken regardless of the R0 to protect populations of people that are most affected by the virus.
The Chain Of Infection as it Relates to the Coronavirus (COVID-19)
The Chain of infection is a cycle used to explain the possible ways an infectious disease can spread. When understanding the chain of infection allows you to have the knowledge of how to protect yourself against the Coronavirus and other types of infections. The following will list the 6 key individual parts of the Chain of Infection and an explanation of each.
1. Infectious Agent
An Infectious Agent can be a Virus, Bacteria, or Fungus that can cause an infection or harm to another living thing. In humans, common infectious agents are influenza, Streptococcus pyogenes (bacteria that can cause strep throat) and Trichophyton, Epidermophyton, and Microsporum which are all types of Fungus that can cause Athletes foot. Identifying the infectious agent is the first step in fighting the infection.
Infectious Agent of COVID-19: New Strain of Single Strand RNA Virus
Reservoirs are places where infectious agents can live and reproduce. Reservoirs help the infectious agent infect new people or animals. Common reservoirs include elevator buttons, doorknobs, surfaces, countertops, and could even be people or animals. A good way to prevent the spread of infection is to clean commonly used surfaces with an antiseptic.
Known Reservoirs for COVID-19: Bats, Pangolins (a rare mammal), Humans, and Commonly Touched Surfaces (all listed above)
3. Portal of Exit
A Portal of Exit is how an infectious agent leaves its reservoir. This could be a cough or sneezing from an infected person. A portal of exit could also be a non-infected person touching a dirty surface like an elevator button or doorknob. Portal of Exits can sometimes be unique to certain infectious agents. For example, HIV cannot be transmitted through a cough however strep throat can.
Known Portal Of Exits for COVID-19: Coughing, Sneezing, or touching a contaminated surface.
4. Method Of Transmission
Method of Transmission is how an infectious agent can infect new people. Method of transmission can be divide into two separate types of transmission, Direct and Indirect. Sometimes Infects agents and display characteristics of both methods of transmission and others with only display the characteristics of one.
Types of Direct Transmission
Direct Transmission is when an infectious agent can be transmitted through physical contact or skin to skin.
Direct Transmission also includes sexual contact and kissing
Contact with contaminated soil by touching or ingesting,
Droplet spread, which refers to spray or particles that come out of an infected person's mouth when they cough, sneeze or even talk.
Types of Indirect Transmission
Indirect Transmission refers to the spread of infection when someone does not make direct contact with an infected individual. An example of this is Airborne infections, or when infectious agents are carried by dust or droplet nuclei (caused by droplet spread) in the air which can be inhaled by a non-infected person.
Vehicles may indirectly spread infections across state lines or to other countries if their cargo is contaminated with the infectious agent.
Another form of Indirect transmission is a Vector. Vectors can include mosquitoes, flies, and ticks or animals (humans too) that serve carry an infectious agent to spread it and double as a reservoir.
Known Method of Transmissions of COVID-19: Droplet Spread, Physical Contact, and Vehicular transport.
5. Portal Of Entry
Portal of Entry refers to how an infectious agent enters a new host. This could be the urethra in males and females, rectum, broken skin like a cut or wound, through blood, the nasal or respiratory system, and the "T-Zone" on a person's face. The T region includes the mouth, nose, and eyes, common places people touch throughout the day.
Known Portals Of Entry For COVID-19: Respiratory system, and T-Zone on your face.
6. Susceptible Host
Susceptible hosts are people that are able to be infected by the infectious agent. Sometimes Infectious Agents can only infect people with weak immune systems or people that have not received a vaccine (If the infectious agent is a virus). In other cases, the genetic makeup or previous conditions can determine susceptibility. Susceptibility also relates to the lethality of the infectious agent which will not be the same for everyone that gets infected.
Known Susceptible Hosts for COVID-19: Bats, Pangolins, Most Humans.
How to Break the Chain of Infection
What is happening now in many countries is the closure of borders, quarantines, and curfews. Many states in the U.S. are also closing bars, restaurants, and schools. These actions are being implemented to help slow down the spread of infection, so hospitals can manage those infected with the coronavirus and other patients that need different forms of care. Patients going into the hospital are not just COVID-19 infectees, cancer patients, those on dialysis, and the elderly are still going to need treatment during this time. Lockdowns and curfews are to ensure that all people who need medical care can receive it as theses measures decrease the spread of infection.
10 Ways You Can Help
Wash Your Hands
Use Hand Sanitizer
Limit time in Public Spaces
Spend more Time at Home
Disinfect commonly used objects in the workplace and at home
Avoid Public Transportation
Avoid contact with those who appear sick
Avoid contact with those who have immune-compromised conditions
Avoid contact with the elderly
Stay home if you are feeling ill