What is Long Covid, and is it similar to ME/CFS?
Long COVID is currently being used as a broad, umbrella-like term: there are different subgroups of Long COVID that fall under that that title. It's not one entity, and that has certainly contributed to some of the complexities around studying it.
At one end of the spectrum, there are conditions and symptoms that are likely due to direct organ damage by the SARS-CoV-2 virus that causes COVID-19, and these include lung fibrosis, myocarditis, or kidney damage. Routine imaging and laboratory tests can identify these types of issues.
Then, at the other end of the spectrum, we have syndromes that are similar to ME/CFS that include disabling symptoms like PEM, fatigue, brain fog, unrefreshing sleep, headaches, dysautonomia, mast cell activation, and orthostatic intolerance. These are often in the absence of abnormalities that are detectable through routine laboratory tests or imaging. The clinical approach for both conditions is directed toward supportive care and symptom management.
Are there notable differences between patients with Long Covid vs ME/CFS?
Long COVID does encompass a number of different subtypes, and the organ system damage we see in a subtype of people previously infected with SARS-CoV-2 is not something that is usually seen in ME/CFS. An example is someone who has lung damage from having acute COVID, and they continue to have shortness of breath and reduced pulmonary function. That's different from what we see with ME/CFS. Another difference would be people with COVID who have had disturbances to their sense of smell and taste. That was something novel that we saw with both acute COVID and in some people who are suffering with Long COVID.
What do we know about what may be causing ME/CFS-like symptoms in patients with Long Covid?
This is an area of active investigation, with the National Institute of Health's REsearching COVID to Enhance Recovery (RECOVER) Initiative being one of the largest efforts around this topic in the United States. Current mechanisms that are being postulated and investigated include persistence of SARS-CoV-2 antigens, abnormal inflammatory reactions, reactivation of latent herpes viruses, gut dysbiosis, microvascular dysfunction, and then viral-induced autoantibodies. It's a pretty lengthy list.
How can growing research in Long Covid contribute to our understanding of ME/CFS?
There are notable similarities among the presentation and the symptoms of both conditions. ME/CFS might have an infectious trigger, and we know that's the case for Long COVID as well. Findings from studies on Long COVID on the causes and therapies that might work can then be potentially investigated and applied to patients living with ME/CFS. If there have been any positives to this pandemic, one is that Long COVID has shone a light on ME/CFS and raised the awareness of the condition.
Are there any promising areas of research in ME/CFS?
Given how little we know about the causes, there are really a lot of avenues worth investigating. Studies on mitochondrial dysfunction, neuroinflammation, glial activation, endothelial dysfunction, and immune dysregulation are all being pursued. Another crucial area to highlight is identifying biomarkers for diagnosis and monitoring the impact of therapy, as well as studies characterizing the mechanism of PEM. PEM continues to be a hallmark of ME/CFS, and it's one of the most baffling and disabling symptoms that patients face.
One area that is a bit different, but also really important, is researching models of clinical care that will allow healthcare providers the time and support necessary to provide the comprehensive care that patients with complex chronic illnesses like ME/CFS and Long COVID really need.