A recent report published in Emerging Infectious Diseases detailed a case of likely human-to-human transmission of an influenza A virus with reduced susceptibility to Xofluza between two siblings in Japan.
“[Xofluza (baloxavir marboxil, Genentech)] susceptibility of influenza viruses, especially among infected children [younger than] 12 years of age, should be closely monitored for public health planning purposes and for making clinical recommendations for antiviral drug use,” Emi Takashita, PhD, a virologist at the National Institute of Infectious Diseases in Tokyo, Japan, and colleagues wrote.
Takashita and colleagues reported detecting 32 mutant influenza A viruses that carried amino acid substitutions indicating reduced susceptibility to baloxavir marboxil during Japan’s 2018-2019 influenza season.
In February 2019, they detected two influenza A (H3N2) viruses in two siblings. The first child was aged 10 years, experienced symptom onset on Feb. 5 and was treated with baloxavir marboxil 12 hours later. The child’s fever resolved within 12 hours, according to the report. The second child was aged 8 months and experienced symptom onset a day later.
H3N2 is a subtype of the influenza A virus.
Deep sequencing analysis of nasal samples from each child revealed that the whole-genome sequences of their viruses were identical. Takashita and colleagues determined that while the viruses had reduced susceptibly to baloxavir marboxil, they were susceptible to the four neuraminidase inhibitors approved for use in Japan.
“The median incubation period of influenza A virus is 1.4 days, and virus shedding can be detected 1 day before the onset of symptoms. Considering that the infant did not have much contact with the outside family, the infant acquiring the mutant virus from the sibling is the most likely option,” they wrote. – by Joe Gramigna
Disclosures: Infectious Diseases in Children could not confirm relevant financial disclosures at the time of publication.