Influenza surveillance among children in a sentinel hospital in Shanghai from 2012 to 2017

ObjectiveTo make an analysis on epidemic and etiological characteristics of influenza on the basis of the surveillance data from the sentinel hospital.

MethodsSurveillance data on influenza like cases and data on pathogen detection were collected for analysis during 2012-2017.

ResultsThe minimum and maximum numbers of outpatients were in 2012 and 2014, respectively.The rest of the years did not show distinct difference in this regard. We found that the constituent proportion of the outpatients was the highest in 1-3 years-old children, followed by 4-7 years old.Children under 1and 8-14 years-old were the least group of outpatients.The difference was statistically significant(χ²=68.41, P < 0.001).Influenza virus positive rate was the highest in 2012(12.42%), lower in 2016 and 2014(respectively were 3.48% and 3.64%).The difference was statistically significant(χ²=61.29, P < 0.001).Dominant strains were influenza B (Victoria)in 2012, influenza A (seasonal H3) in 2013 and 2014, influenza B (Yamagata) in 2015, influenza A (new H1) and influenza B (Victoria) in 2016, influenza A (seasonal H3) and influenza B (Victoria) in 2017.The main infection type of influenza in children younger than 5 and 10-11 years were A (seasonal H3), while aged 6-9 years old were influenza B (Victoria).There was no dominant strains for the children aged 12-14.

ConclusionThe strains of influenza virus are alternatively dominant in children from 2012 to 2017.The spectrum of influenza infections is highly related to the ages of children.