Obstructive pulmonary disease (COPD) is third leading cause of mortality worldwide that induces a high economic and social burden. Cigarette smoking is the most common risk factor, but it is not the only risk factor. There is consistent evidence from studies that airway infection (bacteria or virus or co pathogen) may also develop chronic airflow limitation and COPD. Lower respiratory tract infection during childhood impairs lung growth, causes smaller lung volumes in adulthood. Children with a history of severe respiratory infection has been associated with reduced lung function (FEV1 lowered by 102-650 ml), increased respiratory symptoms in adulthood and developed COPD. HIV patients are increased risk of COPD compared to HIV negative controls. Tuberculosis has also been identified as a risk factor for COPD. Bacterial infection could also contribute to the pathogenesis of COPD including chronic colonization of the lower respiratory tract by bacterial pathogens amplifies the chronic inflammatory response present in COPD and leads to progressive airway obstruction. Viral infection may play a role in driving COPD progression by acting as triggers for exacerbation and subsequent lung function decline. Exacerbations of respiratory symptoms triggered by respiratory infections with bacteria or viruses or coinfection often occur in patients with COPD; a characteristic response with increased inflammation occurs during episodes of infection.