Fatigue During Infections

Fatigue during an infection is a common symptom and results from the body’s response to fighting off pathogens like viruses or bacteria. 

Causes of Fatigue During Infections

Immune system activation: When the body detects an infection, it releases cytokines and other immune mediators to fight off the invading pathogens. These substances cause inflammation, which can lead to feelings of tiredness as the body focuses its energy on immune responses. This fatigue is typically a temporary part of the body’s immune response, often resolving as the infection subsides.

Energy redirection: The body diverts energy from regular activities to support immune functions. This shift can reduce energy availability for daily activities, causing fatigue.

Metabolic changes: Fighting infection requires more metabolic resources, like glucose and proteins, which can drain the body and make it feel weak and exhausted.

Fever and muscle aches: Common symptoms like fever and muscle aches further intensify fatigue. Fever raises the metabolic rate, burning more calories and causing dehydration, both of which contribute to tiredness.

Sleep disruptions: Infections can interfere with sleep due to discomfort, congestion, or fever, which prevents restorative sleep, compounding feelings of fatigue.

Risk Factors

Several factors can increase the risk of fatigue during an infection. These risk factors include a combination of physical, environmental, and lifestyle elements that can make a person more prone to feeling excessively tired when sick.

Age: Older adults are more susceptible to fatigue during infections due to a natural decline in immune system efficiency and physical reserves.

Pre-existing health conditions: Chronic illnesses, such as diabetes, heart disease, asthma, autoimmune disorders, and chronic fatigue syndrome, can increase vulnerability to fatigue as the body is already under stress managing other health issues.

Immune function: Individuals with weakened immune systems, whether due to conditions like HIV/AIDS, cancer treatments, or immunosuppressive medications, may experience more pronounced fatigue due to their body’s compromised ability to fight infections.

Poor nutrition: Inadequate nutrition, especially deficiencies in iron, vitamin D, and B vitamins, can leave the body with fewer resources to support immune function, exacerbating fatigue during illness.

Dehydration: Lack of adequate hydration can increase fatigue, especially if the infection involves fever, which accelerates fluid loss.

High levels of stress: Chronic stress weakens immune responses and increases fatigue, as it strains the body’s resources and often impairs sleep.

Lack of sleep: Poor sleep habits or insomnia can reduce the body’s resilience, making it more susceptible to both infection and the fatigue that accompanies it.

Physical inactivity or overactivity: Those who are very sedentary or, conversely, physically overextend themselves without sufficient rest may feel more fatigue when their bodies encounter the stress of an infection.

Environmental factors: Poor air quality, extreme temperatures, and other environmental stressors can put additional strain on the body during an infection, intensifying fatigue.

Mental health factors: Anxiety, depression, and other mental health conditions can make fatigue more likely and more intense when the body is fighting an infection.

Tips 

Rest is crucial during an infection, as it supports the body’s natural healing processes and helps the immune system work more efficiently. Fighting an infection requires a lot of energy. Rest allows the body to redirect energy from physical activities to immune functions, helping the body respond effectively to pathogens. 

Rest helps modulate the immune response, allowing the body to produce and mobilize immune cells and proteins, like cytokines and antibodies, that target infections. Cytokines are especially critical in inflammation and immune cell signaling and are produced more effectively during sleep.

Physical and mental activities stress the body and demand resources that could otherwise be used for recovery. Rest helps lower blood pressure and heart rate, which can reduce strain on the body and promote healing.

Sleep is particularly restorative, as certain immune functions, including the production of immune memory cells, are enhanced during deep sleep phases. Good sleep helps the body "learn" to recognize pathogens, improving resistance to future infections.

Infection-related inflammation can be physically and mentally exhausting. Rest reduces inflammation by lowering the production of stress hormones like cortisol, which can interfere with immune function when elevated for extended periods. Many symptoms, such as fever, headache, and muscle aches, become more manageable with rest, allowing the body to recuperate without additional discomfort.

Minimize stress through activities like meditation, breathing exercises, or gentle stretching.

Limit physical activity to conserve energy, focusing on light movements only if energy levels permit.

Reduce any sensory input that makes you feel tense or is demanding – such as noise and bright lights. You can also use sensory input to help you rest and relax – like your favorite relaxing music, blanket, fragrance, or a hot water bottle. 

Keep eating and drinking, with as normal a routine as possible and maintain a balanced diet. Little and often may help if your appetite is low, rather than big meals. Increase your fluid intake, especially if you are not managing to eat as much.

If possible, get up and move around slowly and gently a few times each day to keep your body moving and to aid circulation (the movement of blood around your body).

Infections can affect people to different degrees, so give yourself the time you need to recover. The impact afterwards doesn’t always reflect the severity of the infection. Often there will be pressure to get back to your usual activities as soon as possible. Do not rush or push.