Avian metapneumovirus (aMPV) infections are an economical issue for the poultry industry worldwide, and have been associated with upper respiratory tract infections and reductions in egg production in various avian species. The aMPV causes turkey rhinotracheitis (TRT) and is associated with swollen head syndrome (SHS) in chickens, which is usually accompanied by secondary infections that increase mortality. It was first reported in 1978 in South Africa and since then, has been seen in most regions of the world. It has been classified into four subgroups called: A, B, C and D. TRT and SHS are characterised by tracheal rales, sneezing, swollen sinuses, swollen head, and nasal and ocular discharge. The aMPV can lead to a drop in egg production and/or an increase in egg abnormalities in both turkeys and hens. Chickens may have antibodies without exhibiting clinical signs. Transmission requires direct contact among birds and its spread over long distances is uncertain, but wild birds are postulated as probable links. The aMPV infections can be diagnosed by serology (ELISA) and molecular methods (PCR). Good biosecurity and immune interventions are effective and necessary aspects of the control program. Live vaccines predominantly control aMPV infection in poultry flocks, but vaccine virus can be found for extended periods after application that may lead to reversion.