The viral aetiology of influenza-like illnesses in Kampala and Entebbe, Uganda, 2008

Balinandi, Stephen; Bakamutumaho, Barnabas; Kayiwa, John T.; Ongus, Juliette; Oundo, Joseph; Awor, Anna C.; Lutwama, Julius J.

This study identified viral aetiologies in 46.6% of all ILI cases at two health facilities in Kampala and Entebbe, Uganda, a prevalence level similar to that reported in other studies. 22, 23, 24 The identified aetiologies include influenza A and B virus, adenovirus, rhinovirus A, coronavirus OC43 Most of the detected viruses, including parainfluenza virus 1, 2 and 3, influenza B virus, adenovirus, human metapneumovirus and coronaviruses OC43 and 229E, were circulating at prevalence levels that were, in general, similar to those found elsewhere. 12, 14, 26, 27 Influenza A virus was detected in 19.2% of ILI cases, which was higher than the 12% prevalence level that was known to exist from previous observations in the same population. 8 The higher prevalence observed for this virus could be attributed to the timing of this study which was conducted when rainfall is highest in Uganda. It is probable that an outbreak associated with this virus was ongoing during the study period as observed previously. 4, 5, 6 Conversely, rhinovirus A was detected at 7.9% which is lower than the 10 % -25% prevalence levels found in other ILI surveillance studies within sub-Saharan tropics. 13, 14, 16, 28 In the same studies, the prevalence of respiratory syncytial viruses A and B ranged between 5% -21% which is higher than our 3.3% total prevalence for the same viruses. The low prevalence levels observed for these viruses could also be associated with their seasonality in the study population -a variable that could not be established with our current crosssectional data. Also, our ILI case definition was focused more on influenza surveillance and could have been restrictive with regard to the signs and symptoms of other ILI aetiologies. 29, 30 Mixed infections amongst all cases that tested positive for respiratory agents accounted for 14.0% of the findings, with the majority being double infections. The prevalence of mixed infections ranging from 4.5% -70% are reported from other studies, depending on the geographical location of the study area, the diagnostic method used or the general degree of illness in the study population. 24, 31, 32, 33 The high prevalence of mixed influenza A virus and adenovirus infections during a low circulation cycle of respiratory syncytial virus infection has previously been suggested. 34 In our study, the number of mixed infections (n = 24) was not adequate to allow statistical analysis; a more comprehensive study is necessary in order to determine the associations and interactions between these viruses as well as the related clinical outcomes.