With winter approaching, the threat of rampaging respiratory illnesses rises. Influenza is the first virus that comes to mind, and it has been impacting humans for more than 100 years. “Flu season” is discussed every year, and an annual vaccination is produced to protect the most vulnerable and those at high risk. In the winter of 2022, however, it is not the only virus causing concern. With three different respiratory infections circulating, healthcare professionals are warning of a “tripledemic”.
What is a “tripledemic”?
The term “tripledemic” refers to the threat of three respiratory diseases circulating at the same time, namely influenza, RSV (respiratory syncytial virus), and COVID-19 (SARS-CoV-2). It has been popularized in 2022 and follows the term “twindemic”, which was used in 2021 to describe the potential threat of COVID-19 and seasonal influenza circulating simultaneously.
What does current transmission look like?
Major concern of a tripledemic arose in the fall, as an alarmingly high number of severe RSV cases were recorded across the country. Although RSV is a common seasonal infection that generally leads to mild symptoms, fall 2022 saw much more severe cases. In the week ending November 12, the hospitalization rate for RSV cases was 4.8 per 100,0001. For context, the highest rate during that week since 2018 was 1.1 in 2021.
RSV can affect people of all ages, but it’s particularly dangerous for young children. It is a major cause of respiratory illness among kids and the most common cause of bronchiolitis and pneumonia in children younger than one year of age. The explosion in cases led to pediatric hospitals and facilities being overwhelmed. Thankfully, by the end of November, that hospitalization rate had dropped, but the figure of 1.7 for the week ending November 26 remained more than 50% above the highest number recorded since 2018.
While RSV case numbers have begun to decrease, influenza has surged. As of November 26, the number of people hospitalized with the flu had doubled from the week before, with the CDC stating that the hospitalization rate is already higher for this point in the flu season than any year since before 2010. They estimate that there have been at least 8.7 million illnesses, 78,000 hospitalizations, and 4,500 deaths related to influenza2.
Comparatively, COVID-19 cases remain low, although the numbers are beginning to reflect the expected post-Thanksgiving increase. As of December 7, the seven-day average of cases across the U.S. was nearly 62,000, the highest it’s been since mid-September. This also reflects a 68% increase from November 26, when the seven-day average was just below 37,000.
What could be the cause of high case numbers and a “tripledemic”?
There is uncertainty over the exact causes for the surge in and severity of RSV and influenza cases. However, infectious disease experts have cited a few likely contributing factors.
One is that this is, for many people and in many areas, the first “normal” winter season following the onset of the coronavirus pandemic. Little-to-no COVID restrictions remain in most states, and mask mandates in all but government and healthcare settings are almost non-existent. Naturally, without the precautions previously being taken, more people are catching and spreading viruses than in recent years.
The factor that may explain case numbers surpassing levels from pre-pandemic years, however, is that our collective immunity to illnesses such as the flu and RSV has waned. In normal times, many children would have been exposed to RSV or influenza at school, and many of us during our everyday lives. Upon recovery, those infected would have developed antibodies that offer short-term protection against the viruses and reduce the likelihood of experiencing severe illness.
But, following two winters of limited contact and increased protection — whether from social distancing or masks — we’ve been left without these antibodies. As a result, the viruses have more potential hosts to infect, increasing transmission, and people are more susceptible to experiencing the worst symptoms of the virus, increasing hospitalization rates and severe illnesses.
What are the symptoms of each virus?
As RSV, flu, and COVID-19 are all respiratory viruses, it can be difficult to determine which, if any, of the viruses you’re suffering from. Here is a breakdown of what the CDC advises are symptoms of RSV, flu, and COVID-19.
COVID-19 and Flu Symptoms
The CDC says, “both COVID-19 and flu can have varying degrees of symptoms, ranging from no symptoms (asymptomatic) to severe symptoms. Common symptoms that COVID-19 and flu share include:
- Fever or Feeling Feverish/Having Chills
- Shortness of Breath or Difficulty Breathing
- Fatigue (Tiredness)
- Sore Throat
- Runny or Stuffy Nose
- Muscle Pain or Body Aches
- Diarrhea (More frequent in children with flu but can occur in people any age with COVID-19.)
- Change in or Loss of Taste or Smell (Although this is more frequent with COVID-19.)3”
When it comes to RSV, the CDC says, “symptoms usually appear in stages and not all at once. In very young infants with RSV, the only symptoms may be irritability, decreased activity, and breathing difficulties.4” The symptoms of RSV infection usually include:
- Runny Nose
- Decrease in Appetite
Unfortunately, it is possible to contract multiple viruses at the same time, which can lead to a multitude of symptoms. Combined tests that can identify which respiratory disease, or diseases, the patient is experiencing are available and are the best way to provide a clear, definitive result.
How do we avoid the viruses?
While COVID-19 has proven to be primarily spread by airborne particles and droplets, RSV tends to be spread through contaminated surfaces, whereas influenza is somewhere in between as it can be transmitted in both ways. With that in mind, regularly washing your hands and surfaces as well as ensuring you cough and sneeze into a tissue that you dispose of immediately are both useful practices to avoid the viruses.
Although uptake has waned, vaccinations continue to provide the best protection against serious illness caused by COVID-19. The flu vaccine is also crucial for those most vulnerable, particularly this winter, as CDC data suggests that this year’s updated flu shots are a good match for the most prevalent strains of influenza5. While there is currently no approved RSV vaccine for adults, the FDA has granted a priority review to Pfizer’s candidate6.