Sequelae

One of the most relevant examples of sequelae is the long-lasting effects of COVID-19 infection. COVID-19, or coronavirus disease discovered in 2019, is a respiratory infection caused by the SARS-CoV-2 virus. Although symptoms of COVID-19 typically resolve within a few days to a few weeks, some individuals may experience persistent symptoms. These symptoms have been called long-term COVID; those experiencing them are colloquially called “long haulers.” Long-term COVID may also be referred to as chronic COVID, long COVID, post-acute sequelae of SARS CoV-2 infection (PASC), or post-COVID syndrome, as no official term has been established yet. 

Post-COVID conditions can include various health problems that may persist weeks to months after acute illness. Common symptoms include fatigue and cardiopulmonary issues, such as shortness of breath, cough, and chest pain. Neurological issues, such as headaches, sleeping problems, lightheadedness, changes in smell or taste, memory loss, difficulty thinking, and trouble concentrating, are common. Other symptoms may include joint or muscle pain, dermatological conditions, and menstrual cycles. 

While the cause of these continuing COVID-19 symptoms remains unclear, it appears that post-COVID conditions are found more often in individuals who had severe acute COVID-19 illness, especially those who were hospitalized or needed intensive care; in individuals with underlying health conditions; and in individuals who did not receive a COVID-19 vaccine before infection. 

Research on COVID-19 and its prolonged effects on the body has only begun, but long-term complications from COVID-19 are relatively common. Initial findings suggest that 10 to 20% of people who contracted COVID-19 continue to have symptoms or complications of COVID-19 at least one month after diagnosis.

There are many other examples of sequelae in the medical field. Some conditions may be identified retrospectively based on their sequelae. For example, a scar in the lower right quadrant of the abdomen may suggest an appendectomy, and a scar on the upper arm may indicate exposure to the live smallpox vaccine. 

Infection with Streptococcus pyogenes, a bacteria that commonly causes pharyngitis (i.e., strep throat) and skin infections, can lead to post-infectious sequelae. These complications include rheumatic fever, an inflammatory disease that can damage the heart tissue, and post-streptococcal glomerulonephritis, which refers to acute inflammation of the kidneys’ glomeruli. These complications arise even after the bacteria has been eliminated from the body.

Certain neurological conditions, such as a stroke, may leave specific neurological sequelae, including speech disturbances, sensory or motor deficits, and visual disturbances, depending on the areas of the brain affected. Likewise, bacterial meningitis may lead to long-term neurological sequelae, including focal neurological deficits, hearing loss, cognitive impairment, and epilepsy.

Persistently high blood glucose levels in diabetes mellitus may result in several complications of the eyes, kidneys, and nerves. In the eyes, diabetes mellitus can damage the retina, resulting in loss of vision and total blindness. The kidneys’ glomeruli may also damage, leading to chronic kidney disease. Nerve damage may cause a decrease in sensation in the toes and fingers and autonomic nervous system dysfunction, which can affect sweating, passing stool, urinating, and more. Finally, poor blood supply and nerve damage can lead to foot ulcers, which can get infected, sometimes requiring amputation.

Finally, a psychological example of sequelae is post-traumatic stress disorder, which may occur due to a traumatic event—like war or sexual assault—that causes recurrent mental and physical distress.