There are many contagious infections and diseases that can spread quickly. How infectious, or the rate of contagion of a transmissible disease is what determines whether or not the disease is an epidemic. To map the rate of spread, there is an equation used called the R-naught.

As of writing this article, there is a highly contagious virus that is spreading around the world. This new coronavirus, which causes the disease COVID-19, is bringing the best and the worst out in mankind. Since starting as an outbreak in December 2019, this virus has infected millions of people around the world, claiming the lives of many people as a result.

Now, you might be wondering, how did it spread so fast? We may not have the answer, but one way to understand the rate of spread is by looking at R0, or R-naught.

## What is R0?

R0 is a basic reproduction number, which essentially tries to estimate the average number of people who could get the disease from one infected person. That is in an idealized setting, which is a susceptible community where no one has been vaccinated yet. For reference, measles has an R0 of 18, which means that for every one person with measles, 18 other persons will likely contract the measles virus.

## How Do You Make Sense of the R0 Value?

R-naught can be computed as being the number of new cases divided by the number of existing cases. Experts believe that if the R0 value is less than one, the infection will eventually dwindle or diminish. However, if it is 1 or more, the virus will continue to spread.

R0, however, may change from time to time. In the case of COVID-19, the average R0 ranges from 1.5 to as high as 5.5. The huge difference is understandable given that we don’t know much about the virus yet, much less have a cure for it. Our understanding keeps on changing as new data regarding the disease comes to hand.

The factors used in calculating R-naught include the following:

• Infectious period
• Contact rate
• Mode of transmission

Some infections have shorter contagious periods than others. The longer the contagious period is, the higher the chances of spreading. Consequently, it will result in a higher R0 value.

When the contact rate is high, the R0 is also high. When an infected person gets in contact with a large number of people, the disease will spread further. But if they are isolated, either staying at home or at the hospital, then the spread will be minimized.

Also, there are different ways an infection can be transmitted. Some pathogens can be spread through direct contact with blood, saliva, or bodily fluids. Some are airborne. Airborne infections are more contagious, so this mode contributes to a higher R0 value.

## Benefits and Limitations

Even though experts may find R-naught a useful tool in understanding the rate of spread of an infectious disease, there are downsides to using this reproduction number. For one, it can cause panic to the public.

R0 is an average estimation of the potential of a virus or disease to spread. However, many people think that a high R0 means that the disease is going to become a pandemic. That is not always the case, and there is no certainty as to what the future of pathogen would be by solely using R0.

However, R0 helps enable health workers to be prepared for worst-case scenarios. For instance, a super-spreader can infect hundreds of people, which would be a disaster. Knowing that a given disease has a high R0 means that health care providers will be able to proactively set up control measures.

Then, as more people get screened or treated, and experts discover effective protection and treatment, the R0 value will become lower, ideally zero or at least below 1.

## What You Can Do to Help Stop the Spread

Contagious diseases will almost certainly always be a part of the human condition, even when advancements in medicine continue. That said, there are actions you can take to help prevent the spread of pathogens, regardless of whether they are new (novel) or not.

The most basic step is to always wash your hands with soap and water for at least 20 seconds before you eat or prepare foods after you use a public facility or a toilet, and when you come home.

Staying up to date with your vaccinations is also essential to protect yourself. Talk to your doctor about which ones you should get.

When new diseases come out, such as COVID-19, it is important to understand how the infection can be transmitted. That way, you can take the necessary steps to avoid it becoming infected.

This is a trying time for individuals and organizations at every level, and no one should be complacent about any virus. Don’t take your health for granted.

### Jeff Moji

Hi there. I'm Jeff Moji, an engineer, information technologist, and health enthusiast. I have set up this website to explore the best ways to keep fit and healthy as I grow older during this pandemic-prone time. Please keep in touch so we can exchange information and spur one another on.