Influenza viruses are classified into type-A, type-B and type-C, based on differences between an antigenicity of a nucleoprotein(NP) and that of a membrane protein (M). Regarding an influenza type-A virus in the influenza viruses, there are the same number of subtypes as the number of combinations of hemagglutinins (HAs) and neuraminidases (NAs), based on differences in amino acid sequences of HAs and NAs or differences in their antigenicities, in which the HAs are classified into 15 kinds including H1 to H15 and the NAs are classified into 9 kinds including N1 to N9. Among them, the subtypes each causing an infection in human as a host are subtypes H1 to H3 and N1 to N2. In addition, each of an influenza type-A virus (H1 to H3, or N1 to N2) and an influenza type-B virus (hereinafter also referred to as “human influenza virus”) is a causative virus for so-called “influenza (human influenza)” causing a pandemic year after year.
The influenza type-A virus infects not only human but also many mammals and avian species. An infectious disease in avian species caused by the infection in avian species with the influenza type-A virus is “avian influenza”. As an avian influenza virus, which is a causative virus of the avian influenza, all of subtypes H1 to H15 and subtypes N1 to N9 are confirmed. Most of avian influenza viruses do not cause serious symptoms. However, among viruses belonging to avian influenza virus subtypes H5 and H7, there is a virus causing serious symptom in the case where avian species are infected therewith. These are so-called “high-pathogenic avian influenza viruses”, which are apprehensive about a human infection. Since there are some cases of infections and disease contractions in human who has contacted with an animal infected with H9 subtype in the avian influenza viruses, the spread of a human infection is feared.
Presently, in clinical practice, a diagnosis of influenza has been carried out by using a kit for rapidly detecting an influenza virus antigen. Such a rapid diagnosis kit includes a kit employing an enzyme immunoassay (EIA) or an immunochromatography as a principle. There are included a kit for detecting the influenza type-A virus only (see, for example, Japanese Patent Publication Number: JP 2006-67979), a kit for collectively detecting both of the influenza type-A virus and the influenza type-B virus, a kit for separately detecting the influenza type-A virus and the influenza type-B virus, and the like.
However, the rapid diagnosis kit of the patent document 1 is a kit for detecting a wide spectrum of viruses each belonging to the influenza type-A virus, without distinguishing between the human influenza type-A virus and the avian influenza virus. Accordingly, in the case where human shows signs of influenza, it is impossible to determine whether the signs are caused by the avian influenza virus or the human influenza virus. Therefore, it has been required to develop a method for rapidly diagnosing the avian influenza virus.