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Winter Viral Infection Risks for Patients with CLL

In science and medicine, information is constantly changing and may become out-of-date as new data emerge. All articles and interviews are informational only, should never be considered medical advice, and should never be acted on without review with your health care team.

Medically Reviewed by Brian Koffman, MDCM (retired), MSEd

While respiratory infections, especially COVID-19, can occur any time of the year, there is typically an increase in prevalence of coughs and colds during the winter months. Several factors contribute to this trend, but a primary reason is thought to be that people tend to spend more time indoors with closed windows and doors. It appears that 2025 is turning out to be no exception, and those with chronic lymphocytic leukemia / small lymphocytic lymphoma (CLL / SLL) are at higher risk for severe disease due to their compromised immune systems.

The following provides a broad overview of some of the more common infections that are prevalent during the winter.

Masking, hand sanitizing, washing hands frequently, and avoiding poorly ventilated, crowded spaces are all practices that can help reduce the risk of respiratory infections.

Influenza:

  • Influenza cases are rapidly rising across the US, as is the case in most winter seasons.
  • Common current strains are subtype A(H1N1) and A(H3N2).
  • Flu is not a trivial infection, and is often associated with significant fever, cough, sore throat, muscle aches, and shortness of breath. The elderly and the immunocompromised, including those with CLL / SLL, have higher rates of hospitalization and even death.
  • Vaccines can lower the risk of severe disease but are only partially effective and even less so in those with CLL. This year’s vaccines all target the most prevalent strains.
  • Antiviral therapies can help, especially when taken early.

Avian Influenza (Bird Flu):

  • Avian influenza remains relatively rare, and as of this writing, there have been no cases of human-to-human transmission.
  • H5N1 bird flu is widespread in wild birds all over the world. There have been outbreaks in poultry and US dairy cows, resulting in several infections among American dairy and poultry workers.
  • There have been 67 cases, and one death reported in the US.
  • Antiviral therapies used to treat seasonal flu are also effective against bird flu, especially when taken early.
  • Seasonal flu vaccination probably provides little protection, but it reduces the danger of the bird flu and the annual flu virus mixing in an individual.
  • The CDC has issued guidelines to avoid the risk of bird flu, which are provided in a modified form below:
  • Protective actions around wild birds: Avoid direct contact with wild birds and observe them only from a distance, if possible. For example, when refilling a birdfeeder, use protective equipment, including gloves, an N95 mask, and goggles.
  • What to do if you find a dead bird: Avoid contact with wild or domestic birds that appear ill or have died and call to report sick or dead birds.
  • Protective actions around other animals with H5N1 bird flu Avoid unprotected exposure to infected live or dead animals or surfaces contaminated by them.
  • Protective actions if you work with potentially infected dairy cattle: Avoid unprotected direct physical contact or close exposure with cattle and materials potentially infected or confirmed to be infected with the HPAI A(H5) virus.
  • Consuming raw milk: People should not eat or drink raw milk or products made with raw milk. Pasteurized milk is the best way to keep you and your family safe.
  • Preparing food: Eating poultry that is properly handled and cooked in the US is safe. There are recommendations around products from other animals with H5 virus infections, including cattle and milk.

RSV:

  • Respiratory Syncytial Virus (RSV) is also seasonal, with rising levels in the colder weather. It is easily spread between individuals.
  • Most children are exposed to RSV by the age of 1 and experience mild symptoms, but for some it can cause bronchiolitis and pneumonia.
  • It usually presents with symptoms similar to a cold in healthy adults, but in older individuals and the immunocompromised, it can cause severe pneumonia and death.
  • RSV vaccine is approved for high-risk patients, including those with CLL who are over 50, but recommendations on its use can vary. Vaccine responses in the immunocompromised are not as predictable or as robust as those in the immunocompetent.

COVID-19:

  • COVID-19 is very contagious, and infections occur throughout the year, but cases are rising rapidly at the time of this writing.
  • Variants change quickly, but at the time of writing, the most common are XEC, with 44% of cases, followed by KP.3.1.1, with 39% of cases.
  • Vaccines provide some protection that can become fairly robust in many CLL / SLL patients, especially when doses are repeated and the last dose is recent.
  • Pemgarda (pemivibart), a pre-exposure prophylactic (PrEP) monoclonal antibody, retains neutralizing activity against these strains and so should still provide some significant passive immunity.
  • Paxlovid (nirmatrelvir with ritonavir) continues to be effective for all COVID-19 variants, reducing the risk of severe disease and long COVID. Still, it interacts with many medications, so one needs to check with their healthcare team before starting it. Remdesivir and molnupiravir are other good options. Again, early treatment is crucial.
  • Even though the risk is not gone, the number of deaths and severe disease has fallen significantly, even in CLL patients. This is thought to be due to:
    • The virus has mutated and developed a predilection for causing milder upper versus severe lower respiratory infections.
    • Most people have some protective immunity, either from past infections or vaccination, or both.
    • Treatments are much better.

Summary:

It is the season for viral infections. Get vaccinated, discuss Pemgarda with your doctor for COVID-19 PrEP, avoid wild birds, especially sick or dead ones, lower your risk with well-fitting N95 masks and other protective measures, and if you do get sick, get diagnosed and treated quickly.

For more information on infections in CLL / SLL, please read and watch CLL Society’s interview with Dr. Piers Patten from King’s College, London, on Immunity, Infections, and Chronic Lymphocytic Leukemia, and watch the Common Infections with CLL: Prevention and Treatment webinar with Dr. William Werbel from Johns Hopkins Baltimore.