Influenza subtyping may help predict antiviral therapy effectiveness and may assist in treatment of influenza.
Barbara Rath, MD, of the department of pediatrics, division of pneumonology-immunology at Charité University Medical Center in Berlin, and colleagues studied 26 children with influenza A (H1N1) 2009 and nine children with influenza B (Victoria, Yamagata) to examine virus load kinetics and resistance development during oseltamivir (Tamiflu, Genentech) therapy.
The researchers used nasopharyngeal samples to determine viral load and also conducted phenotypic/genotypic neuraminidase inhibitor resistance tests. The researchers measured “patient-specific viral clearance indices along with estimates of the time required to achieve non-detectable virus load.”
Rath and colleagues reported no baseline evidence of oseltamivir therapy in any of the 36 patients before therapy began. Influenza type B had lower viral loads on average than A (H1N1) 2009, which was both drug-resistant and sensitive. Drug-resistant influenza A (H1N1) took longer to reach a non-detectable viral load than sensitive influenza A (H1N1) and drug-sensitive influenza B. Once the virus had cleared, there was no evidence of viral rebound, according to researchers.
“Our data resulting from close virologic follow-up in infants and children suggest that the assessment of baseline viral load measurements (in addition to influenza subtyping) may provide useful to estimate the optimal duration of oseltamivir treatment in the individual patient,” the researchers concluded. “A less-than-expected decrease in viral load during therapy would then point toward resistance development, compliance issues or malabsorption. Clinical parameters in comparison seem to be poor indicators of response to antiviral therapy.”
Disclosure: Dr. Rath reports receiving research funding from Roche.