Virus isolation: Samples are taken from several horses because only a low proportion may be excreting virus. Deep nasal swabs are collected by inserting a long swab 12 inches into each nostril - this requires practice! THE SWAB IS deposited INTO 10 ML TRANSPORT MEDIUM (sterile basic salts solution containing antibiotics), transported at 4^OC and frozen at -70^OC.

In the 1998 UK outbreak egg isolations were negative but 3 viruses was isolated using canine kidney cell cultures with trypsin in the medium, (to cleave Ho) These virus was then used for sequencing.

Antigen detection: Directigen Flu A is a commercial antibody capture ELISA for type A antigens of nucleoprotein in swabs. It does not tell the lab which subtype is involved.

Serology: Following clinical disease a 4 fold increase in serum antibody to H7 of equine 1 or H3 of equine 2 will occur between bleeds taken during the acute and convalescent phase (2 weeks later). This antibody can be detected by haemagglutination inhibition (HI) and will say whether virus is equine 1 or 2.