Community Spread

By Jared Dashevsky, M.Eng. | Last Updated: March 08, 2021

Image by: Lexi Wang

What is Community Spread? 

Community spread occurs when a virus spreads throughout a community and those who become infected aren’t entirely sure how they contracted it. Different public health departments may have more specific or general definitions of community spread.


Key Takeaways

  • When a virus enters your system, it replicates over and over again before spreading to the environment

  • Community spread could indicate that a pathogen is spreading “out of control”

  • Public health interventions are essential to preventing or decreasing virus contraction and transmission


Spreading the Virus

Here’s what the virus’ journey looks like: 

  1. The virus enters your system and sneaks into your cells. 

  2. Within your cells, the virus hijacks some local machinery to replicate itself — the more, the better. 

  3. After the production of sufficient viral progeny, the virus spreads to other parts of the body.

  4. Once the virus is bored with your body, it’ll then shed into the environment to infect others and start a new journey. 

You can shed a virus in different ways, depending on the virus. Poliovirus, which infects nerves and can cause paralysis, sheds in your stools. Coronavirus, which causes the common cold (but also a pandemic), sheds through the mucus in your respiratory tract. This is why it’s essential to cover your mouth and wash your hands after blowing your nose. 

A Scenario

Let’s say you have a cold and don’t wash your hands after blowing your nose. You proceed to shake your friend’s hand, who then rubs their eye. Your friend becomes sick with the same cold you have. This friend doesn’t wash their hands after sneezing, and then cooks a meal for their parents. The parents become sick, and they end up infecting their friends later in the week at a happy hour. The story continues until everyone you know is becoming infected with your cold, but now, no one can pinpoint how they got it!

At this point, there is community spread of the virus.  

Controlling the Spread

Public health officials may implement different measures to prevent the spread of a virus if there’s a severe virus outbreak. First off, good hygiene, such as frequent handwashing and covering your mouth when you cough or sneeze, is an effective way to stop the spread of a virus. If hygiene doesn’t work, then vaccines can do the trick. Vaccines are effective weapons used to prevent you from catching a germ and then spreading it to others. 

If there is no vaccine, public health officials may trace the virus backward from patient number 5 who is infected back to patient number 1. The goal would be to isolate all of these individuals to decrease the risk of spreading the virus to others, which could cause a large-scale outbreak. This is known as contact tracing. 


Outside the Huddle


Reviewed by Geetika Rao, MPH | Edited by Nidhi Mahagaokar, MPH | Fact checked by Julia Radossich, PA-C