Influenza Epidemiology – Explained

By Margaret Walker – Blog Editor

Did you know that key component of public health is epidemiology? But what exactly does this long word mean?

Epidemiology is the study of disease epidemics, or rather it is the study of diseases that start to infect more people than would normally be expected.

There are people and agencies trained to track illnesses and to know if and when certain diseases will become a problem. When new diseases are identified or start to spread (think Ebola, Zika, or Swine Flu), an epidemiologist is on the case!

Influenza is a great example of how viral infections are tracked both within the US and abroad. The Centers for Disease Control and Prevention (CDC) helps to monitor the types and severity of Influenza “flu” Viruses circulating in the US. Every week the CDC updates their website with flu-related information. Maybe you have heard of “Flu Season,” but do you know how many people have gotten sick this year? What about the type of people got sick? How many people were hospitalized, or how many people died from influenza? These are the questions that epidemiologists help us to answer.

How the Flu was tracked in the 2016-17 year:

For some diseases it is possible to test every suspected person who may have the disease. However, in the US, too many people get the flu for us to track every case. Instead we use a sampling system. Certain locations report on every suspected case of influenza. These clinical laboratories then report how many positive cases they have identified. These laboratories are located in all 50 states and Puerto Rico. They also collaborate and report to the World Health Organization to track worldwide strains of the flu.

Note the Weeks are reported as Year then the week of the year. The first week of January of this year was 201701, and this past week was 201709.

As you can see, we are starting to see a decrease in Flu (Type A) cases in the US. The 2016-17 flu vaccination was particularly successful, and the rates of influenza hospitalizations and cases were low compared to prior years. After the epidemic is over, the CDC is able to look back at how well the vaccination worked and will use the data to predict what will happen next year. By working with international organizations, the CDC and WHO can help to inform countries on what vaccination type needs to be made.


The CDC does much more than just track illnesses; they help fund public health studies and projects, monitor the country’s health via long standing surveys, ensure biosafety, and so much more. They are integral to the US public health system, and they need adequate funding to carry out their processes. While the US may need to tighten it’s belt, choosing to slash CDC funding is a short-term gain with potentially generational losses.

Bonus – WHO video on the influenza virus and global surveillance

Sources for more information:

[1] CDC –

[2] WHO –

Cover Photo by Pixabay via Pexels: Creative Commons License

About NPHR Blog (254 Articles)
The is the blog of the Northwestern Public Health Review journal. The blog and journal are both student run and contain research articles, opinions, interviews and other content pertaining to public health.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: