Hyperinflammatory status, also multisystemic inflammatory syndrome (MIS) - 2-4 weeks after infection. In children: Pediatric Inflammatory Multisystem Syndrome (PIMS), which is similar to the Kawasaki syndrome. This intermediary disease phase is described as an immune dysregulation in children and adults. Complications comprise pneumological, cardiovascular, gastrointestinal and mucocutaneous grievances.
No uniform nomenclature, generally "Long-Covid", "Post-Covid" or "chronic Covid", beyond 12 weeks after infection.
In this phase, symptoms are associated with Chronic Fatigue Syndrome (CFS), by patients perceived as the most serious impairment.
After six months, around 10-15% of ambulatory patients still suffer from long-term effects. However, the information about prevalence contained in previous studies is not uniform.
In a British study [Mandal] 384 inpatients with a positive Covid test still suffered almost 8 weeks after discharge
- 70% fatigue,
- over 50% shortness of breath,
- 1/3 cough,
- almost 15% depression,
- almost 40% had abnormal x-ray findings,
- 10% had an elevated CRP (marker of inflammation).
These observations were confirmed by studies from Italy [Sollini], UK, and Sweden [Townsend, Sudre]. The relationship between serious illness and risk factors such as higher age, obesity, or COPD was also documented. In the case of fatigue, it was shown that the duration and extent of the symptoms did not depend on the severity of the acute illness.
Stallmach, see below in 'Outpatient Clinics, sees an association with endothelial dysfunction and vasculitis (vascular inflammation) in the areas of the aorta, iliac and femoral arteries (therapy with platelet aggregation inhibitors). In a comparison of the lungs of Covid-19 patients with those of influenza patients and healthy lungs, clear differences were found in endothelial function, the extent of thrombosis and angiogenesis [Ackermann]. The very pronounced pulmonary changes, including fibrosis, were visible for more than 100 days, but improved over the course of several months [Sonnweber].
According to Stallmach and Lenzen-Schulte, the Long-Covid outpatient clinics are visited by slightly more women (54%) than men, their median age is 51 years (17-77). Almost half of these patients had passed the acute phase without an inpatient stay. Even with moderate acute illness, the disease often progresses for a long time, and this condition can occur at practically any age.
The most relevant long-term symptoms are neurological/psychiatric and cardiovascular (CV) symptoms. Rarely myocarditis seems to persist. There was no lasting direct damage to myocardial tissue by the virus, but extensive endothelitis as detected in autopsies. It is still unclear what long-term consequences such pronounced endothelitis may have [Shchedrygina].