Post COVID Syndrome is defined as the persistence of physical, cognitive and/or psychological symptoms 12 weeks (3 months) after the acute phase of COVID-19, symptoms that cannot be explained by any other diagnosis.

If we define the post COVID syndrome as those COVID symptoms that persist beyond what is expected, and its consequent respiratory involvement, we must be particularly careful not to include here the symptoms derived from the sequelae and severe complications with involvement of various organs after infection, or even with comorbidity due to other pathologies concurrent with the process itself or previous diseases aggravated by the infection.

Thus, it is necessary to distinguish between post-acute COVID (symptoms lasting more than 3 weeks), prolonged COVID (symptoms lasting more than 4 weeks up to 12 weeks) and post-COVID syndrome or persistent COVID (lasting more than 12 weeks).

Post COVID syndrome can result in more than 50 symptoms, most of which occur in multiple forms. Symptoms may fluctuate or cause flares as it is a heterogeneous entity that includes:

• General malaise
• Post-viral chronic fatigue (low threshold for exercise endurance)
• Asthenia (fatigue at rest)
• Dyspnea (shortness of breath)
• Aphonia
• Coughing
• Arthralgia
• Myalgia
• Anosmia (loss of sense of smell)
• Attention disorders
• Difficulty concentrating or mental fog (disorientation, forgetfulness, confusion, and difficulty concentrating)
• Headache
• Epileptic seizures
• Memory changes
• Tachycardia
• Edema
• Sleep disturbance (insomnia)
• Anxiety
• Depression
• Post-traumatic stress disorder (post-ICU patients)
• Multiple organ sequelae
• Effects of severe hospitalization/post-intensive care syndrome

Post-COVID syndrome has been described in patients with mild or severe COVID-19 and regardless of the severity of symptoms in the acute phase.

Approximately 10-65% of survivors with mild/moderate COVID-19 have symptoms of post-COVID-19 syndrome for 12 weeks or longer.

As research progresses, the mechanisms of these SARS-CoV-2 complications and the cascade of dissemination and organs that may be affected, as well as the cytokine “storm” and hemophagocytic lymphohistiocytosis syndrome, are becoming known as major causes of these complications.

The initiation of damage and all these sequelae are probably caused by severe inflammatory responses, thrombotic microangiopathy, venous thromboembolism, and oxygen deprivation.

The cause of the diverse symptomatology of Post COVID Syndrome is fundamentally a multisystemic inflammatory response with associated functional organic wear.

However, to understand the long-term effects of COVID19, why symptoms persist or recur, how and who is affected, and the clinical course and likelihood of full recovery more time and much more research is needed.