Influenza Surveillance Islamabad and Rawalpindi, Pakistan, September 2017 - February 2018 (Preprint)

BACKGROUND Background: Globally 5-10%adults and 20-30%children are affected by influenza annually. Annual epidemics result in 3-5million cases of serious illness and approximately500,000 deaths. In 2008 a sentinel lab-based influenza surveillance network was established in Pakistan in collaboration with CDC having objectives to assess trends of Influenza-like-Illness(ILI) and Severe Acute Respiratory Illness(SARI). OBJECTIVE Objectives: To assess burden of disease, identify risk factors, and recommend control measures. METHODS Methods: A cross-sectional study was conducted based on influenza surveillance data obtained from NICLP from September 2017 to February 2018.Study was done from the data records and samples of suspected ILI patients received from hospitals of Islamabad and Rawalpindi. A case was defined as sudden onset of fever of ≥ 38 C° and cough, with onset within last 10 days. Samples were tested at NICLP for confirmation by RT-PCR. Frequencies were calculated and data analyzed as per time, place and person RESULTS Results: A total of 1500 samples were received out of which 435(29%) were found positive. Among positive samples 246(56.5%) were Influenza-A(H1N1) pdm09,165(38%) were Influenza-A(H3N1) and 24(5.5%) were influenza B.Mean age was 39 years(range 40 days-80 years)while maximum cases were reported from age group 30-39 years(n=77)followed by 50-59 years(n=59).Males were predominant 256(58.8%). Among cases, 21(4.8%) healthcare workers. Travel history was found in 21(4.8%) cases while 35(8%) cases had contact with influenza patients and 14(3.2%) had contact with birds. Among positive cases 262(60%) were reported from Rawalpindi. Majority of cases were reported in January (277) followed by February (112). 31.4% met SARI case definition. Median hospital stay was 5days.During hospitalization 124(26.3%) were ICU admissions, out of them 2(0.42%) were on ventilator, 83(17.6%) were mechanically ventilated. Prevalence of influenza in reported cases was 0.01%.Six confirmed cases died with Case Fatality Rate=1.27%. CONCLUSIONS Conclusion Most cases reported were of Influenza-A (H1N1) pdm09. Based on the results, policy for inclusion of flu vaccination on annual basis is recommended for health care providers and general community.