Long COVID Syndrome (also referred to as Post-Acute Sequelae of SARS-CoV-2 infection, or PASC) refers to a range of symptoms that persist or develop after the acute phase of a COVID-19 infection. While most people recover from COVID-19 within a few weeks, a subset of individuals experience prolonged or new symptoms for months after the infection has cleared.

Common Symptoms of Long COVID;

Research has identified over 200 symptoms linked to long COVID, with these symptoms potentially staying the same, worsening, or fluctuating in severity over time. Some of the most common symptoms include:

• Fatigue: Extreme tiredness that doesn't improve with rest. 
• Shortness of Breath: Difficulty breathing or a sensation of tightness in the chest.
• Brain Fog: Trouble concentrating, memory issues, and difficulty with thinking or processing information.
• Joint and Muscle Pain: Unexplained pain or stiffness.
• Heart Palpitations: Irregular or rapid heartbeats.
• Sleep Disturbances: Insomnia or non-refreshing sleep.
• Headaches: Persistent or recurrent headaches.
• Loss of Taste or Smell: Long-term changes in taste or smell.
• Digestive Issues: Including diarrhea, nausea, or abdominal pain.
• Mood Changes: Anxiety, depression, or mood swings.
• Skin Rashes: Unexplained skin conditions or flare-ups.

Causes and Mechanisms;

Current research suggests that long COVID is a chronic condition triggered by the virus that causes COVID-19, termed an infection-associated chronic condition. While the precise mechanisms remain unclear, researchers have proposed several possible explanations for long COVID:

• Immune System Disruption: The virus may disrupt immune system communication, causing immune cells to mistakenly target the body’s own cells, leading to autoimmune reactions.
• Reactivation of Dormant Viruses: COVID-19 may reactivate viruses that had remained dormant in the body.
• Gut Ecosystem Disruption: The infection may affect the balance of the gut microbiome.
• Viral Persistence: The virus could persist in the gut or other parts of the body, potentially spreading from there.
• Blood Vessel Damage: The virus may impact the cells that line blood vessels.
• Nervous System Effects: The virus could interfere with communication in the brainstem or vagus nerve, which controls various automatic bodily functions.

Because the virus that causes COVID-19 is constantly changing, it is difficult to determine how many people are affected by long COVID. However, some researchers estimate that 10% to 35%of individuals who have had COVID-19 develop long COVID.

Who is Affected?

• Long COVID can affect anyone who has had COVID-19, including those with mild or asymptomatic cases. However, it is more commonly reported in individuals who had severe COVID-19.
• Women, older adults, and those with preexisting health conditions seem to be at higher risk.
• Long COVID can also affect younger, previously healthy individuals, though the risk factors for these cases are still under study.