<unk>  is the only species in the genus<unk> etainfluenzavirus in the<unk>  family Orthomyxoviridae.<unk>  is known only to infect humans and seals. This limited host range is apparently responsible for the lack of associated<unk>  pandemics in contrast with those caused<unk> y the morphologically similar<unk>  as<unk> oth mutate<unk> y<unk> oth antigenic drift and reassortment. There are two known circulating lineages of<unk> <unk> ased on the antigenic properties of the surface glycoprotein hemagglutinin. The lineages are termed<unk> /Yamagata/16/88-like and<unk> /Victoria/2/87-like<unk> es. The quadrivalent<unk>  vaccine licensed<unk> y the CDC is currently designed to protect against<unk> oth co-circulating lineages and has<unk> een shown to have greater effectiveness in prevention of<unk>  caused<unk> y<unk>  than the previous trivalent vaccine. Further diminishing the impact of this<unk> , "in humans,<unk> es evolve slower than A<unk> es and faster than C<unk> es".<unk><unk> <unk>  mutates at a rate 2 to 3 times slower than type A. Nevertheless, it is accepted that<unk>  could cause significant morbidity and mortality worldwide, and significantly impacts adolescents and schoolchildren. The<unk> /Yamagata lineage might have<unk> ecome extinct in 2020/2021 due to COVID-19 pandemic measures.
Influenza B virus
Influenza D virus
Influenza A virus
Respiratory syncytial virus
Hendra virus
Coxsackie A virus
Chinese coronavirus
Coxsackie B4 virus