Why Are Influenza and RSV Going Around so Much?

herd immunity leading to rsv and influenza cases

Many people are asking the question: Why are Influenza and RSV going around so much right now? The short answer to the above question is that the world has lost some immunity against Influenza, RSV, and all the other respiratory viruses that circulate every year worldwide. To understand this, we need to know more about immunity for ourselves and our communities.

RSV, influenza and herd immunity

COVID-19 and Losing Herd Immunity to Other Viruses

What is immunity, and how have we “lost” some immunity during the COVID-19 pandemic? First, we need to know how immunity works in a single person’s body. Then, we can discuss how the overall immunity in a community works to prevent the spread of disease.

Each human being has an extremely complex immune system – a system that includes organs, cells and molecules that work together to protect against disease. There are two basic parts of the immune system: the innate (or non-specific) immune system; and the adaptive (or specific) immune system. See below a comparison of the two parts of your immune system.

Innate (Non-specific) Immune System Adaptive (Specific) Immune System
Can generally recognize foreign things (such as viruses, bacteria, or other harmful things) to your body, but does not adapt or change Adapts or changes to specifically recognize foreign things in your body
Responds rapidly; often your innate immune system can remove the harmful things before your adaptive immune system needs to respond Takes more time to respond; this time is used to produce antibodies and other immune cells that can specifically recognize these foreign things in your body
Does not retain any memory of the foreign things encountered Retains memory of the specific things encountered; thus, when these are encountered again, this part of the immune system can respond more quickly than the first time; this is how vaccines work – they give your adaptive immune system memory to respond quickly when you encounter the thing against which you were vaccinated
Because the response is non-specific, it is usually less effective at removing the foreign things Because the response is specific, it is usually more effective at removing the foreign things

The immunity that we have “lost” over the past three years has been our adaptive immunity. Though our adaptive immune system retains memory of foreign things our body encounters, for many of the respiratory viruses (such as influenza, RSV, and SARS-CoV-2), this memory can quickly wane (become less effective).

Usually, we get exposed to dozens of respiratory viruses each year. This continuous exposure to a variety of different strains of influenza, RSV, and all the other respiratory viruses (including SARS-CoV-2 now), keeps the memory of our adaptive immune systems “up-to-date”. However, for at least 2 years (and flu seasons), most of the world was wearing masks and socially distancing themselves from each other. This made it so we did not encounter the same number of respiratory viruses that we normally do.

I experienced this personally. In a normal year, I will feel the symptoms of 2-4 respiratory illnesses (a.k.a. “colds”). However, from Fall 2019 to Fall 2022 (3 years), I only had 1 total respiratory illness – in 3 years! Because I did not encounter the same number of respiratory viruses in the past 3 years, I am now more susceptible to feeling sick when I do encounter them in the future.

How Does Herd Immunity Affect the Tri-Cities?

why the rsv virus and flu virus

But how does that affect our communities? The answer to this lies in what is called “herd immunity”. The figure below demonstrates the principle of herd immunity. The first box shows that when nobody is immune to a disease, it spreads very quickly through a community. The second box shows that when some people are immune to a disease, it still spreads through a community, but some people are protected. The third box shows that when most people are immune to a disease, not only are they directly protected from the disease, but they also indirectly protect those that are not immune from getting the disease. This third box is how vaccines work to protect our communities, and how natural immunity to respiratory viruses works. 

In a normal year, enough people are exposed to respiratory viruses to build up some immunity. This limits the spread of a virus in a community – like box 3. However, because of wearing masks and socially distancing for the past 3 years, we are probably more like box 2, where only some of us have normal immunity to respiratory viruses. This is causing respiratory viruses like influenza and RSV to spread more quickly and effectively than normal.

herd immunity leading to rsv and influenza cases

What You Can Do to Prevent RSV and Influenza

So what can you do? Below are some important things you can do to help limit the spread of respiratory illness in your community:

  1. Get vaccinated. Each year the U.S. produces an influenza vaccine that can protect you from any or at least serious illness from the influenza virus. And if you feel it is safe, the SARS-CoV-2 vaccine has been shown to protect people from serious illness and death.
  2. Wash your hands. Despite all of our advances in medicine in the past two centuries, washing your hands is still the most effective way to keep disease from spreading. And in the case of respiratory illness, cover your mouth when you cough or sneeze. And if you feel symptoms, stay home and rest and wear a mask when in public.
  3. Get tested – so you know what you have! At Tomorrow’s Health, you can come in and get tested without a doctor’s order. If you test positive for influenza and you are within the first 48 hours of symptoms, you can be effectively treated. If you test positive for Strep throat, there is a 100% effective treatment for that. If you test positive for RSV, you can know that you need to avoid contact with infants, the elderly, and anybody with a compromised immune system.

Give us a call today or visit our laboratory in Kennewick, WA.


  1. https://theconversation.com/what-is-herd-immunity-and-how-many-people-need-to-be-vaccinated-to-protect-a-community-11635

Brent L. House, PhD | Owner/CEO | Tomorrow’s Health Laboratory

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