Influenza-associated morbidity and mortality in Tunisia

Abstract Background Influenza is a highly contagious viral infection representing a public health problem worldwide with more than 10% of the population affected each year. In addition, severe complications and deaths may occur especially among high-risk groups. Our objectives was to assess the severity of influenza in Tunisia from 2015 to 2017 and to identify the isolated circulating viruses. Methods Basedon the network of ILI (Influenza-like illness) and SARI (Severe acute respiratory infection) Sentinel Sites and the National Influenza Center, we conducted a descriptive analysis of all data collected from 2015 to 2017. The case definitions of ILI and SARI were those recommended by WHO. Data entry was using Epi-Data and data analysis using SPSS-20. Results The total number of SARI cases during 2016-17 season was 614. The hospitalization rate was 0.7% which was higher than the 2015-16 season (0.19%). The majority of these severe cases were males (60,3%) and the group aged more than 65 years was the most affected. Comorbidities were reported in 58,7% of the cases, especially cardiovascular diseases, obesity and asthma. In 2016-17, the viruses identified in SARI cases were type A(H3N2) (47,7%), type B (40,9%) and type A (H1N1) pmd09 (4%). The lethality rate was lower than in the previous season (0.32% vs 20%) with two deaths reported in February. These deaths were due to virus B and virus AH3N2, comparing to 77% of deaths due to virus A (H1N1) pmd09 the season before. Conclusions Influenza severity vary from a season to another. The 2016-17 season was marked by higher rates of hospitalization but a lower lethality rate. This may be due to a lower circulation of the type A (H1N1) pmd09 virus, which virulence is much discussed. Influenza surveillance remains essential to detect any emerging novel pathogen and to guide decision-makers for future strategies. Key messages Seasonal influenza epidemics continue to have significant morbidity and mortality. Epidemiological and virological surveillance are highly essential for an early detection of epidemics and novel strains.