Time trend and predictors of lab positivity among suspected cases in the post pandemic phase of H1N1
Sitanshu Sekhar Kar, Kalaiselvi Selvaraj, Archana Ramalingam, Gautam Roy
Abstract
Background
WHO declared Influenza A H1N1 to have entered the post pandemic phase on August 10, 2010. Continued surveillance activities are recommended in the post pandemic phase to watch over the trend, severity and impact of Influenza like illnesses (ILI).
Aims
This study aimed to document the epidemiological profile of lab positive H1N1 cases in post pandemic period from August 2010-December 2014 in nodal H1N1 surveillance centre of Puducherry.
Methods
The study analysed secondary data collected during the period August 10, 2010 to Dec 2014 from ILI suspects attending a tertiary care hospital, for the Integrated Disease Surveillance Project (IDSP). Demographic details, lab positivity based on Real time –PCR technique for H1N1, clinical symptoms and outcomes were extracted. Data were analysed using STATA version 11.0. Independent predictors of lab positivity rate were identified using logistic regression analysis. Time trend of frequency of suspected cases and lab positivity rate were performed using time series plots.
Results
A total of 2065 suspected cases were reported, of whom 197 cases were positive for H1N1 (lab positivity rate 9.5%). Being an adult (OR: 1.6; 95% CI:1.1 - 2.3; p=0.02), management in in-patient settings (OR: 2.5; 95% CI:1.3-4.7; p=0.001), history of contact (OR: 2.7; 95% CI1.5 - 4.5; p=0.0001) and history of travel (OR: 2.3; 95% CI: 1.2 to 4.3; p=0.01) were the independent predictors for lab positivity. Death rate among lab confirmed cases was found to be 9.6 %. After 2012, the trend of laboratory confirmed H1N1 cases became a plateau. One needs to screen 35 suspected cases to capture one lab confirmed case of H1N1 in 2014.
Conclusion
Lab positivity was seen among 9.5% of cases and the independent predictors were severe cases, adult patients, positive history of contact and travel. The number needed to screen to get one lab positive H1N1 case is 35 suspected cases.
Full Text:
WHO declared Influenza A H1N1 to have entered the post pandemic phase on August 10, 2010. Continued surveillance activities are recommended in the post pandemic phase to watch over the trend, severity and impact of Influenza like illnesses (ILI).
Aims
This study aimed to document the epidemiological profile of lab positive H1N1 cases in post pandemic period from August 2010-December 2014 in nodal H1N1 surveillance centre of Puducherry.
Methods
The study analysed secondary data collected during the period August 10, 2010 to Dec 2014 from ILI suspects attending a tertiary care hospital, for the Integrated Disease Surveillance Project (IDSP). Demographic details, lab positivity based on Real time –PCR technique for H1N1, clinical symptoms and outcomes were extracted. Data were analysed using STATA version 11.0. Independent predictors of lab positivity rate were identified using logistic regression analysis. Time trend of frequency of suspected cases and lab positivity rate were performed using time series plots.
Results
A total of 2065 suspected cases were reported, of whom 197 cases were positive for H1N1 (lab positivity rate 9.5%). Being an adult (OR: 1.6; 95% CI:1.1 - 2.3; p=0.02), management in in-patient settings (OR: 2.5; 95% CI:1.3-4.7; p=0.001), history of contact (OR: 2.7; 95% CI1.5 - 4.5; p=0.0001) and history of travel (OR: 2.3; 95% CI: 1.2 to 4.3; p=0.01) were the independent predictors for lab positivity. Death rate among lab confirmed cases was found to be 9.6 %. After 2012, the trend of laboratory confirmed H1N1 cases became a plateau. One needs to screen 35 suspected cases to capture one lab confirmed case of H1N1 in 2014.
Conclusion
Lab positivity was seen among 9.5% of cases and the independent predictors were severe cases, adult patients, positive history of contact and travel. The number needed to screen to get one lab positive H1N1 case is 35 suspected cases.
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