Long-lasting cough in an adult German population: incidence, symptoms, and related pathogens

Studies of the incidence of pertussis in adults have shown that it accounts for only 5-15% cases of prolonged coughing. We assessed the burden of suffering related to prolonged coughing and tried to identify further causative agents. Based on a sentinel study with 35 general practitioners in two German cities (Krefeld, Rostock), with 3,946 patients fulfilling the inclusion criteria, we estimated the incidence of prolonged coughing in adults. In 975 of these outpatients, PCR and/or serology for adenovirus, Bordetella pertussis and B. parapertussis, human metapneumovirus, influenza virus A and rhinovirus, parainfluenza virus, Mycoplasma pneumonia, and respiratory syncytial virus (RSV) were performed. Treatment data were extracted for a subgroup of 138 patients. Descriptive statistics, including Kaplan-Maier curves were generated. Yearly incidence ranged between 1.4 and 2.1% per population in the two cities. Adult patients sought medical attention only after a median of 3 weeks of coughing. Irrespective of smoking and unrelated to the identified pathogens, the median duration of coughing was 6 weeks, with an interquartile range of 4-11 weeks. In 48.3% of patients, possible pathogens were identified, among which adenovirus (15.1%), RSV (7.5%), B. pertussis (5.6%), and influenza viruses (4.0%) were most often found. Symptoms were not indicative of a specific agent and a total of 64% of patients received antibiotics. Prolonged adult coughing requiring medical attention prompts substantial healthcare use. Apart from B. pertussis, a broad range of pathogens was associated with the symptoms. However, patients sought medical attention too late to guide efficacious therapeutic interventions using the diagnostic tests.