Introduction
Influenza is an acute respiratory illness(2) caused by the influenza viruses. These viruses have led to a number of outbreaks and epidemics, causing significant morbidity and mortality globally. Type A and B are the main human pathogens, with the former being very common and associated with most large-scale and serious outbreaks.(3) Type A virus possesses the ability to periodically change the structure of its antigen (antigenic shifts and antigenic drifts). . These antigenic shifts and antigenic drifts are linked to annual pandemics. The incubation period of Type A influenza virus is ~24-48 hours, after which symptoms such as rapid onset of fever, headache, fatigue, and muscle pain, start to appear .(4) These symptoms are associated with manifestations of disease of the respiratory tract, including cough, sore throat and rhinitis.(5) In these patients, a common and dangerous complication is bacterial pneumonia. The mortality rate is high and mainly attributed to refractory hypoxia.(6)
The widespread H1N1, subtype influenza A virus, appeared first during spring 2009 in Mexico from where it spread swiftly across the globe.(7) On June 11, 2009, a phase 6 pandemic alarm was declared by the World Health Organization (WHO), suggesting that the 21st century’s initial influenza pandemic had started. The height of the local influenza outbreak had gone by in the majority of the countries by the close of 2009.(8) The novel H1N1pdm09 virus still circulates (with antigenic evolution and variability) among the population, and plays a part in the usual seasonal epidemics of influenza.(9) The global 2009 H1N1 virus led to extensive transmission among the United States and other countries, and accounted for approximately 61 million cases, 274,000 hospital admissions, and 12,470 deaths.(10),(11)
Till now, internationally over 214 countries and territories have reported lab-confirmed cases of H1N1, with 17,919 deaths(12), as well as enormous economic effect covering both direct and indirect expense.(13) In a new case series, the lag between the manifestation of the symptoms and starting the treatments has been linked to unfavorable results.(14) As regards the patients diagnosed with influenza, longitudinal reviews are required to draw an estimation of the fraction of cases that advance to death, respiratory failure, or need extended hospitalization.(15) The earliest case of swine flu (H1N1) in Pakistan, confirmed by laboratory testing, was found on the 10th of August 2009, with occasional cases reported every year thereafter. Pakistan was afflicted by the H1N1 epidemic from winter 2015 until February 2016, during when over 240 confirmed cases were reported.(1) But regarding hospitalizations of the affected patients, its clinical manifestations and outcomes, limited studies have been carried out in Pakistan. Our aim was to evaluate the clinical manifestations and results in patients admitted to the hospital having H1N1 influenza virus infection. The objectives of this research were to evaluate the clinical features and its outcomes in H1N1 influenza patients being treated at NWGH & RC, Peshawar.