Exposure and outcome measures:
The
primary exposure was clinical respiratory illness (CRI) defined as
self-reported history of ≥2 respiratory symptoms (fever, cough, sore
throat, runny nose and difficulty breathing) within prior 7 days of date
of onset of AMI (32,
33). The secondary exposure was baseline
qRT-PCR confirmed influenza A or B. In the current study the main
predictor variables of interest were CRI and laboratory evidence of
Influenza, and the outcome variables were AMI and AMI sub-types.