Emerging respiratory pathogens is a term used to refer to acute respiratory infections that may have a serious public health impact; including infections caused by either emergence of new variants of known respiratory pathogens (e.g. influenza A(H3N2) or emergence of as yet unknown pathogens.
Influenza viruses that normally circulate in animals are called “variant” viruses when they are found in people. They also can be denoted by adding the letter “v” to the end of the virus subtype designation.
Most commonly, human infections with variant viruses occur in people with exposure to infected animals. The majority of human infections with variant influenza viruses do not result in person-to-person spread.