In this latest video from MedCram, Dr. Seheult gives an overview of where we are in the current influenza and COVID-19 season. With all of the current infections going on, there’s been a lot of focus on fever—particularly how the body’s response to infection, such as flu or COVID-19, might be influenced by elevated temperatures. Understanding the role of fever and when to treat it is critical, as it can be both a sign of infection and an important part of your immune system’s defense. Let’s dive into how fever interacts with the immune system, especially in the context of viral infections like flu and COVID-19, and the latest research that sheds light on this complex process.
Flu Season Update: Hospitalization Trends
As we approach mid-January, we’re well into the flu season for 2024-2025. According to estimates, flu-related hospitalizations are tracking similarly to previous years, but it’s still unclear whether this season will peak like it did in the 2017-2018 flu season or resemble a more moderate year like 2021-2022. While the hospitalization numbers are still rising, there’s hope that things may soon begin to level off, signaling the end of the flu peak for this season.
However, the flu isn’t the only virus making waves right now. COVID-19, although in the background compared to earlier years, continues to affect individuals, and understanding fever’s role in both illnesses remains an important area of research.
The Role of Fever in Fighting Viral Infections
Fever is often seen as an unpleasant symptom of infections like the flu and COVID-19, but it’s also a key part of your body’s immune defense. The body’s immune system responds to infections by increasing its temperature, which serves as a natural response to viral invaders. But when is fever beneficial, and when should we treat it?
Fever and Its Benchmarks
Fever is generally defined as a body temperature of 100.4°F (38°C) or higher. Temperatures between 98.6°F (37°C) and 100.4°F (37-38°C) are considered normal and don’t typically warrant any treatment. But once the temperature rises to 102.2°F (39°C), we see a clearer indication of a fever, and temperatures exceeding 104°F (40°C) can become dangerous.
In most clinical settings, fevers aren’t treated until they reach the 100.4°F threshold. Between 100.4°F and 102.2°F, common fever-reducing medications like acetaminophen or ibuprofen may be used to help make the patient more comfortable. But, there’s a philosophical debate about whether treating a fever is always the right choice, as fever can actually be beneficial in fighting infections.
Why Fever Helps: The Immune System’s Response
Your immune system is key to fighting infections, and it works through two main mechanisms: the innate immune system and the adaptive immune system. The innate immune system is your body’s first line of defense and is activated when the body detects foreign invaders like viruses. It includes immune cells such as macrophages, natural killer cells, and dendritic cells, which are important for producing substances like interferons that help fight viruses.
Research has shown that even a subtle increase in body temperature can boost these immune responses. For example, studies have demonstrated that just raising the body’s temperature from 37°C (98.6°F) to 38°C (100.4°F) triggers a significant increase in antiviral gene expression—an early step in your body’s fight against infection.
New Research on Fever and Immune Activation
Recent studies, including one published in Nucleic Acids Research, have provided insight into how even a mild fever can significantly enhance immune responses. The research found that increasing the body temperature by just 1°C (from 37°C to 38°C) activated antiviral genes related to the innate immune system. This suggests that mild fevers, which may not even be classified as “fevers” by traditional standards, could play an important role in boosting immune function.
Interestingly, the study also showed that elevated temperatures from 37°C to 39°C (102.2°F) can prime the immune system even more, leading to increased production of key immune factors like nitric oxide and interferon—both of which are critical for antiviral defense. This raises the question of whether we should be cautious about reducing fevers with medication, especially in the early stages of illness.
A Historical Perspective on Fever Treatment
Historically, there’s been a split in how fever is treated. Some treatment approaches, like those used in military hospitals, involved the use of medications like aspirin to reduce fever, which often led to improved comfort but didn’t necessarily reduce the fatality rates of infections. On the other hand, hospitals like the New England Sanitarium took a different approach by encouraging elevated body temperatures through hydrotherapy. Their method—using warm towels to induce sweating—was shown to reduce early pneumonia rates, despite a slightly higher death rate from pneumonia.
These historical approaches highlight the complexity of fever management: while it’s uncomfortable, fever may actually support immune function, helping the body fight off infections more effectively.
Should We Treat Fever?
The current consensus in medical practice generally advises against treating fevers unless they rise above certain thresholds (e.g., 102.2°F or higher). Research has shown that fever can be beneficial in activating immune responses, and interfering with this process could delay recovery. However, there are exceptions, particularly for individuals with low thresholds for complications like seizures, or for those with underlying conditions that make fever more dangerous.
In some cases, allowing a fever to run its course between 38°C and 39°C may even be preferable to taking fever-reducing medications. This is especially true in mild cases where the immune system has the opportunity to build a strong defense response.
Takeaways and Practical Guidance
- Fever and Immunity: A mild fever can be beneficial in stimulating your body’s innate immune system, helping it fight viral infections more effectively.
- When to Treat Fever: In general, treating fever may not be necessary unless the temperature exceeds 102.2°F (39°C). Focus on comfort and hydration, but avoid overusing fever-reducing medications unless necessary.
- Body Temperature and Viral Infections: Subtle increases in body temperature—even below the “fever” threshold—can enhance immune responses like the production of interferon and other antiviral factors, aiding in the fight against infections like flu and COVID-19.
- Listen to Your Body: Every person is different, and what works for one individual may not be appropriate for another. Always consider the specific circumstances, especially for people with underlying health conditions or those experiencing very high fevers.
As we continue to monitor the flu and COVID-19, understanding how fever plays into the body’s defense mechanisms is crucial. Fever may not just be a symptom of infection—it could be a sign that your immune system is ramping up its response, helping you recover faster.
LINKS / REFERENCES: Weekly US Influenza Surveillance Report: Key Updates for Week 2, ending January 11, 2025 (CDC) | https://www.cdc.gov/fluview/surveilla…
Preliminary Estimated Flu Disease Burden 2024-2025 Flu Season (CDC) | https://www.cdc.gov/flu-burden/php/da…
How to take your temperature (Mayo Clinic) | https://www.mayoclinic.org/how-to-tak…
As We See It (Life & Health) | https://northernlightshealtheducation…
Early Treatment with Pegylated Interferon Lambda for Covid-19 (NEJM) | https://www.nejm.org/doi/full/10.1056…
Hyperthermia in humans enhances interferon-gamma synthesis and alters the peripheral lymphocyte population (Journal of interferon research) | https://pubmed.ncbi.nlm.nih.gov/3132509/
Body temperature variation controls pre-mRNA processing and transcription of antiviral genes and SARS-CoV-2 replication (Nucleic Acids Research) | https://academic.oup.com/nar/article/…