Hospital-based surveillance of influenza A(H1N1)pdm09 virus in Saudi Arabia, 2010-2016

Abdalla, Osman; Mohammed, Mutaz; Hakawi, Ahmed Mohammed; Aljifri, Alanoud; Abdalla, Mohamed; Eltigani, Sara; Mujib, Sahibzada Azhar; Assiri, Abdullah

Six hundred and eight patients died with A(H1N1) pdm09 as the principal cause of death during these seven years. Given that the policy was to limit laboratory testing for A(H1N1)pdm09 to admitted cases only, the reported confirmed cases do not reflect the actual overall disease burden. The CFR based on the suspected cases as the denominator [0.54% (CI: 0.50-0.58)] should be interpreted with caution. As well, CFR based on the confirmed cases as the denominator [3.56% (95%CI: 3.29-3.85)] represents the fatality among the severely morbid cases only. In line with international studies. 21,22 the highest CFR was reported among the age group 60 years and above in all years, with 17.1% in 2011 and 15% in 2013, and this fits into the international data where influenza and pneumonia were the seventh cause of death in this age group. The next highest affected was the age group 30-59 years with 10.5% in 2013 and 9.5% in 2011. The overall fatality rates showed a decline over time with an age shifting towards elders.