What to Know about the ‘Twindemic’ of 2021

Influenza and COVID-19 are both widespread viral illnesses that can overwhelm hospital systems on their own. Both are shaping up to make this winter especially tough.

Dec. 22, 2021 5   min read

On their own, influenza and COVID-19 affect tens of millions of people in the United States each year. Based on current health trends, the next few months will likely see an increase in both viruses.

There are currently 119 cases of influenza in Monroe County, according to the New York State Department of Health. At all hospitals in Monroe County, there are 164 patients with COVID-19.

Maryrose Laguio-Vila, MD, is chief of the Infectious Disease Unit with Rochester Regional Health and shares her expertise about what to expect heading into the winter months.

Last year vs. this year

In 2020, public health officials saw unusually low levels of circulating flu being detected.

There are several different reasons for those low levels of flu. Some of them stemmed from significant challenges with testing supplies. Many of the materials needed to create and process COVID tests are the same materials used to create and process flu tests. This wasn’t an issue only in New York or even the U.S.; those shortages were happening worldwide.

Beyond the limited availability of testing materials, other factors that may have played a role in a lower overall number of flu cases include:

  • COVID-related lockdowns
  • Wearing masks/face coverings in indoor public settings
  • Increased hand hygiene
  • Increased physical distancing

In 2021, a rise in flu cases has been observed over the last several weeks. The New York State Department of Health is deeming influenza to be widespread – meaning there are multiple cases in more than half of New York counties.

“In terms of diagnostic testing, our labs will screen patients for flu if their COVID test is negative,” Dr. Laguio-Vila said. “We are actively looking for influenza cases when it comes to testing.”

The ‘Twindemic’

The term ‘twindemic’ refers to two pandemics occurring simultaneously.

As influenza becomes more widespread and thousands of new COVID-19 cases are diagnosed each day, we are facing the significant challenge of potentially combatting two pandemics that will happen at the same time.

For individual patients, there is the possibility of contracting both viruses at the same time.

“We don’t quite know yet what the type of severity of illness would be, but since both viruses cause severe lung infections, it is rational to assume that they could be worse together,” Dr. Laguio-Vila said.

The effect of two respiratory infections at the same time are well documented. When a patient is infected with influenza, the virus infects the lungs. The infection increases the odds of a bacterial co-infection in the lungs. Flu changes the immunology of the body’s lung tissue, which could make it more susceptible to bacteria. Those who have both bacterial pneumonia and the flu become much sicker.

From a public health standpoint, the most significant concern is the strain it would cause on healthcare systems. There are already staffing concerns for hospitals and long-term care facilities. If the number of patients increases to a point where these locations reach their maximum capacity for patients, and the number of patients who can be discharged to go to rehabilitation or nursing homes does not go up at the same time, patients who are sick and need treatment cannot be admitted.

In short, more flu cases could cause more stress on healthcare staff and the whole system.

Public health officials and medical personnel have been promoting mask wearing and physical distancing and vaccination against these viruses. Dr. Laguio-Vila strongly encourages everyone to keep focusing on those ways of preventing the spread of illnesses.

“We need to continue to promote these methods of prevention, and there is a lot of fatigue around masking and hand hygiene,” Dr. Laguio-Vila said. “But now as flu season is ramping up alongside the holiday season, we need to double down, get vaccinated, and try to prevent both flu and COVID infections.”

Prevention and treatment

Healthcare systems need to empower primary care and urgent care centers for early testing for both flu and COVID-19.

If providers can diagnose an illness early enough, they can prescribe medication to a patient that could help them reduce how long they are sick and the potential spread of the virus. This can reduce the number of hospitalizations.

To best protect ourselves and those around us, people can follow precautions recommended by public health officials:

  • Get vaccinated for flu and/or COVID-19 – including a booster shot as available
  • Wear a mask
  • Practice physical distancing
  • Avoid crowded public spaces with unmasked individuals
  • Practice good hand hygiene

If a person is not feeling well and exhibiting symptoms that could potentially be indicative of flu or COVID-19, they are strongly encouraged to stay home from work, school, or socializing.

If the potential exists for the illness to be either flu or COVID, the person should isolate themselves, get tested as needed, and take care of themselves.

Even with the potential for a ‘twindemic’, Dr. Laguio-Vila said people who are feeling sick to the point where they want to go a hospital or urgent care should go and not worry that they will not be seen.

“Knowing which infection you have can greatly impact the kinds of treatments you can get,” Dr. Laguio-Vila said. “If you end up being sick enough to be hospitalized, you can get a variety of treatments. Seeking out a diagnosis from a healthcare provider is critically important.”

Rochester Regional Health provides several ways to meet with patients, ranging from in-person visits to telemedicine to video conferencing. Patients can ask their primary care provider if these options are available and right for them.


Scientists around the world are discovering new information about COVID-19, vaccines, treatments, and more every day. Rochester Regional Health is keeping you informed about the latest developments and research.

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