Dr John Chia has noted that corticosteroids given during an acute viral infection seems to be a recipe for precipitating ME/CFS. That is to say: acute infection + corticosteroids = ME/CFS In this presentation by Dr John Chia (found on the DVD of the Invest in ME International ME/CFS Conference, London 2010), Chia talks about the factors and events his ME/CFS patients report just prior to them developing ME/CFS. One factor that Chia says he hears of hundreds of times, occurring just prior to the onset of ME/CFS, is that the patient was given corticosteroids (steroids) such as prednisone or prednisolone at a time when the patient was acutely ill with a viral infection. From hearing this story time and time again from his ME/CFS patients, Chia thinks that taking steroids while fighting an acute enterovirus infection is a recipe for disaster, as it seems to precipitate ME/CFS. Why might corticosteroids be given for a viral infection? If you watch this part of the video, Dr Chia says the skin rash that may be caused by an acute enterovirus infection can look like chicken pox, measles, German measles, or hives. Dr Chia says that if, for example, people suddenly become ill and develop a skin rash from an acute enterovirus infection, they may go to the emergency room, and the emergency room doctor will look at the rash, and might suspect the rash to be hives, since enterovirus rashes can look identical to hives. So the ER doctor will question the patient as to what he ate beforehand. If the patient just happened to eat some shellfish, then the ER doctor may assume that the patient's rash is indeed a hives rash, caused by allergy to the shellfish, and so will put the patient on a course of steroids, like prednisone or prednisolone, as this is the normal treatment for hives. So the patient has a fierce acute enterovirus infection, and needs a strong and robust immune response to fight off this infection, yet receives immunosuppressing corticosteroids, because the rash was diagnosed as hives, which is a disaster. Similarly, if a patient came down with an acute viral infection, and its symptoms were suggestive of asthma, they may also get corticosteroids, because that's how you treat asthma. Dr Chia says on the video: So it appears that if you take immune suppressing drugs like corticosteroids at a very critical stage when the body is trying to fight off a fierce acute enterovirus infection, one presumes that these steroids may weaken the immune response to such a degree that the enterovirus is now able to get a much better foothold in the body tissues — ie, the virus may penetrate deeper into the body, penetrate into more tissue compartments of the body — and so this enterovirus infection is never eradicated, and it becomes a chronic, persistent infection, and the patient may then come down with ME/CFS a few weeks or months after. Dr Chia says on another video: So acute infection + corticosteroids = ME/CFS may explain the reason that a subset of patients developed chronic fatigue syndrome. EDIT: unfortunately that Dr Chia video presentation linked to above had to be taken down from YouTube, because Invest in ME claimed a copyright infringement. This 45 minute Dr Chia video can be bought from Invest in ME. It comes on the following DVD set: Invest in ME International ME/CFS Conference, London 2010. (Though all the relevant information from that Chia video, about corticosteroids precipitating ME/CFS, has been transcribed in the quotes given above in this post).