What is ME/CFS? Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex and disabling disease that affects many parts of the body, including the brain and muscles, as well as the digestive, immune and cardiac systems, among others. ME is classified as a neurological disorder by the World Health Organization. Who can develop ME/CFS? ME/CFS affects men, women and children of all ages, ethnicities, and socioeconomic backgrounds. 75-80% of people with the condition are female. Around 25% of people with ME/CFS experience severe symptoms, leaving them housebound or bedbound. While estimates of how many people have ME/CFS vary, it is thought that around 0.4-1% of the population is affected. This means that up to 250,000 Australians have the condition. What are the symptoms of ME/CFS? People with ME/CFS experience a wide range of symptoms. A common misconception is that people with ME/CFS have 'chronic fatigue', and are just tired. Chronic fatigue is a symptom of many conditions (for example, heart disease, cancer, multiple sclerosis, anaemia and ME/CFS), but it is not a condition in its own right. Persistent and profound fatigue is just one symptom of ME/CFS, as it is with a number of other conditions. The central feature of ME/CFS is post-exertional malaise (PEM), which means that symptoms get worse after physical or mental activity. PEM is very disabling and causes fluctuations in a person’s health: what they may be able to do one day, they might not be able to do the next. The level of activity that triggers PEM varies. For some, it may be a short walk or writing a homework assignment. For people who are more severely unwell, it could be brushing their teeth or reading a sentence of a book. PEM is often delayed and can last days, weeks or months, making the illness difficult to manage. Other common symptoms include: sleep dysfunction widespread pain in muscles or joints cognitive difficulties, such as confusion, or problems with concentration or memory sensitivity to noise or light light-headedness or dizziness difficulty with being upright gastrointestinal problems such as nausea, abdominal pain, bloating and irritable bowel syndrome flu-like symptoms problems with temperature regulation sensitivities to food, medications or chemicals What causes ME/CFS? The cause of ME/CFS is currently not known, although a number of factors may be involved, including: infection (which is the most common trigger, but is not universal) environmental toxins physical trauma (such as surgery or car accident) genetics (like many other chronic diseases, ME/CFS can run in families, although the specific genes involved haven’t yet been identified and more research is needed) physical, mental or emotional stress may also contribute to the onset of the condition For some people, ME/CFS comes on suddenly. For others, there is a gradual onset over months or years. It is not currently understood why there are these differences in how the illness starts. While there are currently no diagnostic biomarkers or tests for ME/CFS, there are many biological abnormalities that researchers have found in people living with the condition. These include an abnormal physiological response to exercise, altered immune function, changes in the bacteria in the gut, and impaired energy production. Access related pages easily using the links below: Diagnosis Treatment and management ME/CFS – what's in a name? What is fibromyalgia?