It is currently unknown why most people recover fully within two to three weeks and others experience symptoms for weeks or months<unk> er. Although the exact processes that cause<unk>  remain unknown, a number of mechanisms have been suggested. A March 2021 review article cited the following pathophysiological processes as the predominant causes of<unk> : * direct toxicity in virus infected tissue, especially the lungs * ongoing inflammation due to post-infection immune system dysregulation * vascular injury and ischemia caused by virus induced hypercoagulability (tendency to form internal clots) and thromboses (internal blood clots) * impaired regulation of the renin-angiotensin system related to the effect of SARS-CoV-2 on ACE2 containing tissue In October 2020, a review by the United Kingdom's National Institute for Health Research hypothesized that ongoing<unk>  symptoms may be due to four syndromes: * permanent damage to the lungs and heart, * post-intensive care syndrome, * Post-viral fatigue, sometimes regarded as the same as myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS), and * continuing COVID-19 symptoms. Other situations that might cause new and ongoing symptoms include: * the virus being present for a<unk> er time than usual, due to an ineffective immune response; * reinfection (e.g., with another strain of the virus); * damage caused by inflammation and a strong immune response to the infection; * physical deconditioning due to a lack of exercise while ill; * post-traumatic stress or other mental sequelae, especially in people who had previously experienced anxiety, depression, insomnia, or other mental health difficulties; *inhibited oxygen exchange as a result of persistent circulating blood plasma microclots; and *development of various autoantibodies after infection. Similarities to other syndromes<unk>  is similar to post-Ebola syndrome and the post-infection syndromes seen in chikungunya and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) which is often triggered by infection and immune activation and was previously also known as “post-viral fatigue.” The pathophysiology of<unk>  may be similar to these other conditions. Some<unk>  patients in Canada have been diagnosed with ME/CFS, a "debilitating, multi-system neurological disease that is believed to be triggered by an infectious illness in the majority of cases". Lucinda Bateman, a specialist in ME/CFS in Salt Lake City in the US believes that the two syndromes are identical. There is need for more research into ME/CFS; Anthony Fauci, chief medical adviser to the US government, said that COVID-19 is a "well-identified etiologic agent that should be very helpful now in getting us to be able to understand ME/CFS". Risk factors According to a King's College London study initially posted on 21 October 2020 risk factors for<unk>  may include: * Age – particularly those aged over 50 * Obesity * Asthma * Reporting more than five symptoms (e.g. more than cough, fatigue, headache, diarrhoea, loss of sense of smell) in the first week of COVID-19 infection; five is the median number reported Women are less likely to develop severe acute COVID but more likely to develop<unk>  than men. Some research suggests this is due primarily to hormonal differences, while other research points to other factors, including chromosomal genetics, sex-dependent differences in immune system behavior, and non-biological factors may be relevant.
Long COVID
Zero-COVID
FACE AIDS
NHS COVID-19
Rapid Reviews: COVID-19
PLOS Pathogens
HIV/AIDS in Asia
HIV/AIDS in Europe