Study of the Epidemiological Features and Clinical Manifestations of the Preceding Epidemic of Influenza A (H1N1) as a Guide for Dealing With the 2015 Outbreak in the Qazvin Province, Iran

Background: In 2009, a pandemic associated with a new type of influenza A virus (H1N1) affected many countries worldwide. After five years of silence, in 2015 we encountered another outbreak of H1N1 influenza A. Objectives: The present study aimed to study the epidemiological and clinical features of this disease in the cold and dry climate of Qazvin province, Iran in the last epidemic, during 2009. Patients and Methods: This was a cross-sectional study in which the demographic characteristics and clinical manifestations of confirmed cases of influenza A virus (H1N1) in the province of Qazvin were investigated. The definite diagnosis of cases was performed using real time Polymerase Chain Reaction (PCR) on oropharyngeal washing specimens from adults and throat swabs from children and severely ill patients. Results: During the time course between July to December 2009, 76 confirmed cases of influenza A (H1N1) were discovered in the province of Qazvin. The mean age of patients was 25.67 ± 16.9 years. The most affected people were students and housewives. Coughing was found to be the most common clinical symptom (96.1%) followed by fever (92.1%), myalgia (48.5%), and diarrhea and vomiting (34.2%). In laboratory confirmed patients, 62 were hospitalized and two cases deceased. Regarding the total population of the Qazvin province (1,100,000), the rate of hospitalization was calculated at 5.42 per 100,000 individuals, with a mortality rate of 0.175 per 100,000 individuals (3.2% of hospitalized cases). Conclusions: Concerning the higher prevalence of disease in younger age groups, and more severe disease in high-risk groups, including overweight patients and pregnant women, the authors recommend special attention to clinical symptoms such as diarrhea and vomiting, cough, myalgia and fever in patients with cold symptoms. Also, for severely ill patients, the allocation of adequate intensive care units should be of prime importance.