Impact of Influenza Virus-associated Severe Acute Respiratory Infections in Three Districts in 2018 at Gharbia Governorate Egypt

Abstract

Abstract Background Influenza remains a major contributor to substantial global morbidity and mortality. Reliable influenza burden estimates are needed for a better understanding of the disease impact in vulnerable groups. There are limited data on disease burden in Egypt. Although hospital‐based severe acute respiratory illness (SARI) sentinel surveillance was established in El-Mahala Fever hospital at Gharbia governorate in 2009, determining the catchment population for the hospital was one of the biggest challenges. Objective This study first aims to determine the catchment population for El-Mahala Fever hospital and calculate the incidence of seasonal influenza infections. Second, the study seeks to estimate the percentage of hospitalizations associated with SARI in public and private sectors in the three districts of Gharbia governorate. Methods This study was done by using the World Health Organization (WHO) manual to estimate the incidence of influenza‐associated SARI in the sentinel surveillance site of Gharbia governorate. Hospital database for 2018 was screened for SARI patients to obtain demographic, lab testing, and outcome data. Three districts that reported the most SARI cases were identified. Incidence was calculated using influenza‐positive SARI cases as the numerator and catchment population as denominator, as defined through the hospital admission survey (HAS). Catchment population was calculated as the proportion of pneumonia cases at El-Mahala fever hospital among all pneumonia admissions in all hospitals in the three districts multiplied by the total population. Results The catchment population of El-Mahala Fever hospital was estimated at 10.6% (190,096) persons (95% CI, 10.56-10.65) of the total population residing in the three districts of Gharbia governorate. Meanwhile, hospitalizations of SARI cases in the private sector was estimated at 15.28% (134) cases (95% CI, 12.96-17.83). At El-Mahala fever hospital, 180 SARI cases were identified; their median age was 23 [IQR: 2-53], 45% were males. Of the total SARI cases, 33.3% (60) were confirmed as influenza; their median age was 21 [IQR: 3-51], 42% were males. Influenza A (H3N2) virus predominated, representing 55.0% of patients, followed by A(H1N1) 26.7% and Flu-B virus 18.3%. Influenza prevailed in winters and spring; no deaths from influenza were reported. The overall incidence of influenza-associated SARI was 32/100,000 (95% CI, 25-41). The rate was significantly higher in very young (<2 years) and old (>65 years) patients (282 and 215/100,000 population respectively, p<0.001 for both). Incidence was insignificantly higher in females and residents of urban areas than corresponding groups (32 vs 30/100,000 and 34 vs 31/100,000 population, p=0. 8 and 0.7, respectively). Conclusions The methods detailed in the WHO Manual for estimating disease burden associated with seasonal influenza were successfully operationalized in the three districts of Gharbia governorate; it can be used in other districts to estimate catchment population and incidence of influenza-associated SARI. Influenza viruses are associated with a substantial burden of severe illness requiring hospitalization, especially among extreme age groups. In order to estimate influenza burden in other risk groups than those based on age, it is imperative to conduct further research. Keywords: Influenza; Incidence; Sentinel Surveillance; Respiratory Infections; Egypt