Estimation of the attributable fraction of respiratory viruses
detection to illness
We used unconditional logistic regression to estimate the attributable
fraction (AF) of respiratory viruses-associated hospitalization and
outpatient consultation by comparing the respiratory viruses detection
rate among ILI or SRI cases to those of controls (outcome variables in
the models). The attributable fraction was estimated from the virus
specific odds ratio (OR) obtained from the multivariable regression
models as follows:
[1]
Subsequently we estimated the individual respiratory viruses detection
rate associated with illness among ILI and SRI cases
(InflDetectRateIll ) from the observed detection
rate (InflDetectRateObs ) as follows:
InflDetectRateIll =
InflDetectRateObs*AF [2]
This analysis was implemented overall and within the following age
categories: <5, 5-44 and ≥45 years of age. All estimates were
obtained from multivariable models that included the different
respiratory viruses investigated in this study, HIV infection, and
underlying medical conditions as covariates as previously described
[11Hellferscee O,
Treurnicht FK, Walaza S, et al.
The Fraction of
Rhinovirus Detections Attributable to Mild and Severe Respiratory
Illness in a Setting of High Human Immunodeficiency Virus Prevalence,
South Africa, 2013-2015. J Infect Dis.2019 ;219(11):1697-1704. doi: 10.1093/infdis/jiy725.,22Tempia
S, Walaza S, Moyes J, et al.
Attributable Fraction
of Influenza Virus Detection to Mild and Severe Respiratory Illnesses
in HIV-Infected and HIV-Uninfected Patients, South Africa, 2012-2016.
Emerg Infect Dis. 2017 ;23(7):1124-1132. doi:
10.3201/eid2307.161959.].