Post-infectious diseases are not new. In neurology, as in other specialties, the diagnoses are multiple following an infection. It could happen immediately after, a few weeks later, a few months later, or sometimes even longer. This is not necessarily the same as what we call relapsing-remitting illnesses, because once symptoms begin to become chronic, there is never any real return to baseline health.
There are delayed effects from many of the exposures we are subjected to, which include not only infectious organisms but also environmental contaminants, radiation, and even necessary treatment regimens such as chemotherapy.
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In children, we see post-infectious diseases such as acute demyelinating encephalomyelitis (ADEM), transverse myelitis (TM), and infection-related febrile epilepsy syndrome (FIRES) as examples.
In adults, we see diagnoses such as Guillain Barre syndrome (GBS) and chronic fatigue syndrome myalgic encephalomyelitis (MECFS) as examples. Indeed, there has been recent research and dialogue regarding the potential of other diagnoses such as multiple sclerosis (MS) and Alzheimer’s disease (AD) as a post-infectious process.
We have seen the long term effects of COVID-19. Commonly referred to as Long Covid or Long Haul or Post Acute SARS-CoV-2 Infection (PASC). Post-Covid symptoms include chronic fatigue, exercise intolerance, difficulty breathing, cognitive changes, headache, dizziness, hypersensitivity, sleep dysfunction, neuropathy, difficulty focus and more. This is very similar to what is seen in MECFS, so it is believed to be more of a systemic post-infectious disease.
The mechanisms underlying the pathophysiology of post-infectious syndromes are still being elucidated. We have seen evidence of immune challenge through direct infection, but also chronic immune activation due to molecular mimicry, meaning that a piece of the virus or bacteria – specifically, something called the antigen – that causes the immune response, looks very much like a piece of some of our cells. As a result, the immune system becomes fundamentally confused and continues to fight against an “autoantigen”. This can progress to an autoimmune disease.
Other mechanisms that have been researched and considered include the release of pro-inflammatory mediators from mast cells (“cytokine storm”), induction of a hypercoagulable state causing the formation of microclots which obstruct small vessels and disrupt blood flow, and, interestingly, chronic infection from the persistence of the organism itself as there has been identification of viral particles in tissue samples.
More research is needed to better understand the elements of this disease so that more effective treatments can be offered. We need to know more about the cause of the different symptoms and what underlies the post-acute nature of infectious diseases. There is some urgency to this issue due to the current pandemic and the possible chronic effects it may have.
While acute Covid infection is to be feared, the consequences are also worrying. Acute infection can and has led to increased deaths among the population. But post-infection symptoms can lead to long-term morbidity as opposed to mortality. This can affect the quality of life for those affected and reduce overall functionality and productivity.
It does not appear to be related to the comorbidities present in an individual. It appears to be happening seemingly at random thanks to future research that may be able to identify those most vulnerable, whether due to genetics or past exposures. And doctors can only offer palliative and supportive care in the hope that time, along with care, will help improve the health of their patients.
These long-term effects can occur regardless of the severity of the infection. Many patients with long-term Covid report having only mild symptoms with the acute infection, which would have been improved or resolved only to get worse after a certain period later.
No one is ever ready for a chronic illness and the changes it causes in the way we live our lives. Tasks that were once simple, like going to the grocery store, doing laundry, or playing with our kids, are no longer so and often require logistical planning and time to recover.
We all often take our health for granted. Patients often say “but I have been so healthy my whole life”. But we are healthy until we are not. We don’t feel any pain until we do. We sleep well until we are no longer sleeping. We move well until we can no longer. These chronic changes can feel like a loss of freedom for many and a continual questioning of the meaning of our lives.
I see a lot of fear in my long Covid patients. It is a fear of who they are now and a fear of who they will be and what they will become. Living in a “new normal” is not easy and living in uncertainty is not ideal. We can only try to live with gratitude for now. As Nietzsche once said, “He who has a why to live can endure almost any way.”