Abstract
Epidemiological data about determinants of influenza A virus (IAV) in the Pakistani population is scarce. We aimed to conduct a prospective hospital-based active surveillance study from October 2015 to May 2016 to identify potential risk factors associated with IAV infection among patients with influenza-like illness (ILI) and severe acute respiratory illness (SARI). Surveillance was conducted in Lahore General Hospital, selected as a sentinel site in Lahore District, Pakistan. Nasal/throat samples were collected along with epidemiological and clinical data from enrolled patients. Real-time reverse-transcription polymerase chain reaction (rRT-PCR) was performed to identify IAV and its subtypes (H1N1pdm09, H3N2). Data were analyzed to determine risk factors and risk markers associated with IAV infections. A total of 311 suspected ILI and SARI cases were enrolled in the study, and among these 50 were IAV-positive. Of these 50 confirmed cases of IAV, 14 were subtyped as H1N1pdm09 and 15 were H3N2; the remaining 21 were untyped. A final multivariable model identified four independent risk factors/markers for IAV infection: exposure history to ILI patients within last 7 days and gender being male were identified as risk factors of IAV infection, while use of antibiotics prior to hospital consultation and presence of fever were identified as risk markers. We concluded that adopting nonpharmaceutical interventions like hand hygiene, masks, social distancing, and where possible, avoiding identified risk factors could decrease the risk of IAV infection and may prevent imminent outbreaks of IAV in the community.
Highlights
Influenza is a highly infectious, mild to severe respiratory disease of birds, humans, and other animals that is caused by influenza viruses
We analyzed a set of risk factors and risk markers for influenza A virus (IAV) infection, and the results indicated that exposure history to influenza-like illness (ILI) patients within last 7 days, gender, presence of fever, and use of antibiotics prior to hospital consultation are associated with IAV infection
Our multivariable multiple logistic regression model indicated that history of exposure to the ILI patients within the last seven days is independently associated with a high risk of developing IAV infection
Summary
Influenza is a highly infectious, mild to severe respiratory disease of birds, humans, and other animals that is caused by influenza viruses. E WHO stressed the importance of routine influenza surveillance incorporating clinical and epidemiologic data collection for risk factor identification as critical components of a comprehensive strategy in addition to laboratory diagnosis of various influenza subtypes [3]. Modifications in influenza vaccine strategies from 2019 in response to influenza epidemics by various subtypes highlighted the clear stratification of risk factors, subsequently improving the understanding of clinical management of severe disease [4]. Evidence-based identification of risk factors associated with increased risk of influenzaassociated morbidity and mortality in Pakistan could be used to target high-risk groups for interventions and to mitigate the spread of the disease. We conducted a hospital-based sentinel surveillance study and aimed to assess the relationship of various risk factors and risk markers with IAV infection in Lahore District, Pakistan, from October 2015 to May 2016
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