Reassessment of high prevalence human adenovirus detections among residents of two refugee centers in Kenya under surveillance for acute respiratory infections

Abstract

Human adenoviruses (HAdVs) were previously detected at high prevalence by real-time reverse transcription-polymerase chain reaction (rRT-PCR) in the upper respiratory tract of residents of two Kenyan refugee camps under surveillance for acute respiratory infection (ARI) between October 2006 and April 2008. We sought to confirm this finding and characterize the HAdVs detected. Of 2148 respiratory specimens originally tested, 511 (23.8%) screened positive for HAdV and 510 were available for retesting. Of these, 421 (82.4%) were confirmed positive by repeat rRT-PCR or PCR and sequencing. Other respiratory viruses were codetected in 55.8% of confirmed HAdV-positive specimens. Species B and C viruses predominated at 82.8%, and HAdV-C1, -C2, and -B3 were the most commonly identified types. Species A, D, and F HAdVs, which are rarely associated with ARI, comprised the remainder. Viral loads were highest among species B HAdVs, particularly HAdV-B3. Species C showed the widest range of viral loads, and species A, D, and F were most often present at low loads and more often with codetections. These findings suggest that many HAdV detections were incidental and not a primary cause of ARI among camp patients. Species/type, codetections, and viral load determinations may permit more accurate HAdV disease burden estimates in these populations.

Keywords: Kenya; adenovirus; real-time reverse transcription-polymerase chain reaction (rRT-PCR); respiratory infections.

FIGURE 1

Box-and-whisker plots showing median and interquartile distributions of Ct values obtained with confirmed positive specimens by HAdV species/type and where species/type could not be determined (STND)

FIGURE 2

Distribution by Ct values (left axis) of 511 specimens that screened positive (gray bars) for HAdV by rRT-PCR and 421 specimens that were subsequently confirmed positive (red bars) by repeat rRT-PCR or PCR and sequencing. Percentages of HAdV-positive specimens (right axis) with codetected respiratory viruses (open circles) or with species B or C HAdVs identified (filled circles). Data averaged over 4-Ct value bins and fitted with linear regression lines. Linear regression equations and correlation coefficients of determination (R²) presented adjacent to the respective lines. Ct, cycle threshold; HAdVs, human adenoviruses; rRT-PCR, real-time reverse transcription-polymerase chain reaction

FIGURE 3

Temporal distribution of HAdV species A, B, C, D, and F (bars) and type 3 (line) identified at Dadaab and Kakuma refugee camps. Limited surveillance began in October 2006 in Kakuma and in May 2007 in Dadaab