IRIS does not have a widely accepted definition, although an international attempt has been made. A definition for resource-poor countries has been developed and cases need to meet three criteria . IRIS is characterized by the worsening or appearance of new signs, symptoms or radiographic abnormalities, occurring after the initiation of HAART, and not the result of TB treatment failure or another disease process. It is therefore a diagnosis of exclusion. It is often defined as transient but can last many months. It is usually seen when the TB is microbiologically controlled, but cases can occur with viable organisms isolated on culture. The features of IRIS are an apparent worsening/progression of TB occurring after initiation of HAART, with no other apparent cause. Response to corticosteroids does not confirm the diagnosis of IRIS.