Differences of clinical manifestation between influenza subtypes

Abstract

Background: Primary viral and secondary bacterial pneumonia are most significant complications of influenza and associated with intensive care unit (ICU) admissions with high mortality. Rapid Influenza Diagnostic Tests (RIDTs) detect influenza virus within several hours and lead to early antiviral therapy early. The objective of this study was to identify the differences in clinical manifestation and complication between influenza A and B.

Methods: We performed a retrospective observational study to evaluate clinical manifestations and complications of identified influenza infection by RIDTs and Reverse-transcriptase polymerase chain reaction (RT-PCR) respiratory virus technique during the influenza outbreak period at one medical center in South Korea (Dec. 2014 – Mar. 2015).

Results: 184 viruses were identified as influenza A and B: 153(80.2%) viruses as influenza A(H3N2); 11(5.7%) viruses as influenza A(H1N1)pdm09; and 19(9.9%) as influenza B. There were no significant difference in clinical symptoms between the subtypes. Influenza A had a higher incidence of pneumonia than influenza B, although the differences were not statistically significant: H3N2/H1N1/B 17.5%/27.3%/5.3% (p=0.256). Also, both in mortality and use of mechanical ventilation there were no significant difference (p=0.471 & p=0.604). 169(91.8%) patients were diagnosed by RIDTs, while the other 15 patients were diagnosed by RT-PCR respiratory virus technique.

Conclusions: Influenza patients showed no significant differences in incidence of clinical symptoms, pneumonia and complications between subtypes. A combination of RIDTs and RT-PCR test improved the detection rate of influenza infection of clinically suspicious patients.