Morbidity burden, seasonality and factors associated with the human respiratory syncytial virus, human parainfluenza virus, and human adenovirus infections in Kenya

Background: Human respiratory syncytial viruses (HRSV), human parainfluenza viruses (HPIV), and human adenoviruses (HAdVs) cause a substantial morbidity burden globally. Objective: We sought to estimate morbidity burden, assess seasonality, and determine factors associated with these respiratory viruses in Kenya. Methods: The data were obtained from Kenyan sites included in the Köppen-Geiger climate classification system. We defined the proportion of morbidity burden by descriptive analysis and visualized time-series data for January 2007–December 2013. Logistic regression was used to identify factors associated with infection outcomes. Results: The morbidity burden for HRSV was 3.1%, HPIV 5.3% and HAdVs 3.3%. Infants were more likely to be infected than other age groups. HRSV exhibited seasonality with high occurrence in January–March (odds ratio[OR] = 2.73) and April–June (OR = 3.01). Hot land surface temperature (≥40 °C) was associated with HRSV infections (OR = 2.75), as was warmer air temperature (19-22.9 °C) (OR = 1.68), compared with land surface temperature (<30) and cooler air temperature (<19 °C) respectively. Moderate rainfall (150-200 mm) areas had greater odds of HRSV infection (OR = 1.32) than low rainfall (<150 mm). Conclusion: HRSV, HPIV and HAdVs contributed to morbidity burden, and infants were significantly affected. HRSV had a clear seasonal pattern and were associated with climate parameters, unlike HPIV and HAdVs.