Flu – post-infectious complaints – post-flu fatigue syndrome
What happens after flu?
Fatigue, malaise, lack of strength, breathlessness, reduced exercise tolerance, sweating, muscle and joint pain, sometimes swollen joints, and neurological symptoms such as headaches, tingling and muscle weakness can accompany and follow infection with the flu virus (influenza), as well as other viral and bacterial diseases. Dr Šime Mijić, a physiatrist-rheumatologist at Faktor Zdravlje Polyclinic, explained in detail what can happen and how we can help when the acute symptoms of flu have stopped but we still have complaints.
Physiotherapy is often the best way back to your usual activities. Contact your physiatrist or rheumatologist, who can rule out or confirm other diseases such as rheumatoid arthritis, polymyalgia rheumatica and reactive arthritis, which is common after infections.
During influenza (flu) and other infectious viral and bacterial diseases, joint and muscle pain, fatigue and weakness are symptoms that tell us how serious the condition is. When other symptoms and signs are added, such as cough, fever, loss of appetite and a rash, a doctor should examine the person carefully so that these complaints do not lead to a deterioration in health.
Musculoskeletal complaints are an integral part of flu, especially pain in the lower back and legs, both at rest and on movement. Any significant exertion is difficult for the patient, especially while they have a fever.
Interestingly, once the acute symptoms and fever have stopped and the cough has settled, some of the musculoskeletal symptoms may persist in the form of fatigue, loss of strength, a need for more rest, and a lack of agility and of the will to be active. Post-bacterial forms of arthritis are well known, such as rheumatic fever, in which there is a painful migratory arthritis accompanied by joint swelling, redness and warmth.
Infectious and post-infectious arthritis, whether bacterial or viral, often presents as transient synovitis (temporary swelling of the joint and joint capsule). Besides flu, post-infectious arthritis is common with rubella, parvovirus B19 and hepatitis B.
There is a genetic predisposition to reactive arthritis, especially the bacterial form, which is associated with the major histocompatibility complex, i.e. the human leukocyte antigen HLA-B27, but also with other genes and antigens. T lymphocytes react with the antigen and produce an immune response. Viral particles or parts of their DNA are rarely isolated; more often we cannot identify them in the synovial (joint) fluid, which supports the hypothesis of a cell-mediated immune reaction. Molecular mimicry is based on the interaction between a microbial antigen and the body's own proteins, together with stimulation of a Th2-mediated autoimmune response. Cytokines produced by Th2 cells are involved in joint damage.
The pathogenesis of post-viral arthritis is much more complex, as it often does not meet the classic definition of reactive arthritis. With rubella, varicella zoster, herpes simplex, CMV and adenoviruses, we sometimes isolate the virus or parts of it in the affected tissue. Interestingly, post-infectious arthritis more often affects the lower limbs (ankles, knees), and does so asymmetrically. Neurological manifestations are common: polyradiculoneuritis (Guillain–Barré syndrome), facial nerve palsy and encephalitis. Multiple sclerosis can also develop after an infection, and a number of rheumatological and neurological diseases can worsen.
Dizziness is often the result of a viral inflammation of the vestibular nerve, accompanied by loss of balance and faintness, both at rest and on movement.
Muscle complaints, i.e. muscle inflammation, which we call myositis, are accompanied by raised inflammatory markers (CRP, ESR) and raised levels of muscle enzymes such as CPK, LDH and aldolase.
Lyme disease, i.e. infection with Borrelia (Borrelia burgdorferi), is also an example of a bacterial arthritis that is common in our part of the world, and it can affect the brain, skin and joints.
Post-infectious arthritis is characterised by
– asymmetric arthritis of 2–5 joints, especially in the lower limbs, accompanied by enthesitis (inflammation where a tendon attaches to bone) and dactylitis (diffuse swelling of a finger or toe).
– a recent infection in the medical history
– with or without a symptom-free interval after the infection (usually 2–4 weeks)
A post-infectious syndrome involving joint and muscle pain requires careful evaluation by an infectious disease specialist, a rheumatologist and a physiatrist. The condition needs careful clinical and laboratory evaluation to reach an accurate diagnosis, provide adequate treatment and establish the prognosis. Post-infectious arthritis has a good outcome and prognosis with symptomatic treatment, and recovery usually comes after a few weeks (usually around 6 weeks). It rarely requires specific treatment, e.g. with glucocorticoids or disease-modifying drugs.
– exclusion of other causes such as septic arthritis, spondyloarthropathies (spondyloarthritides), juvenile arthritis and systemic lupus.
