Burden of influenza A (H1N1)pdm09 infection among tuberculosis patients: a prospective cohort study

Background Influenza and tuberculosis both cause significant morbidity and mortality worldwide.

Therefore, this study aimed to estimate the burden of influenza A (H1N1)pdm09 virus infection among human tuberculosis patients and the general population.

Methods A prospective cohort study was conducted among a cohort group (TB positive patients) as exposed and a comparison group (general population) as non-exposed.

A total of 304 participants were recruited in both groups and followed for a period of 12 weeks.

Of the 304 concurrently enrolled individuals, 152 were TB-positive patients (cohort group) and 152 were from the general population (comparison group).

To calculate the sample size, the power of study was kept at 80% for detecting a difference at 5% alpha level assuming the 25% prevalence of respiratory viruses in cohort group compared to 12.5% in general population.

An oropharyngeal swab was taken from a participant with symptoms of influenza-like illness (ILI).

Samples were tested by conventional reverse transcription polymerase chain reaction (RT-PCR) for the detection of influenza A (H1N1)pdm09.

All statistical analyses were conducted using R software.

Results A total of 95 participants developed influenza-like illness (ILI) symptoms.

Among these, 64 tested positive for influenza A(H1N1)pdm09, of which 39 were from the exposed group and 25 were from the non-exposed group.

During the 12-week period of follow-up, the influenza A (H1N1)pdm09 incidence rate was 20 per 1000 people.

The risk of testing positive for influenza A (H1N1)pdm09 was 1.66 times higher in the exposed group compared to the non-exposed group.

The cumulative incidence indicated that 25% of the TB cohort and 16% of the comparison group were at risk of getting influenza A (H1N1)pdm09 during the 12 weeks of follow-up.

Conclusion Participants from the TB cohort had a higher incidence of influenza A (H1N1)pdm09 than the general population suggesting that they should be prioritized for influenza vaccination.