Further tests, in addition to antigen detection:

Virus isolation is used either at the start of a new virus disease or at the start of an outbreak to allow further characterisation of the virus and comparisons of it to other viruses e.g. for foot and mouth disease virus or equine influenza virus.

Some newer tests now involve detecting viral nucleic acid.

Antibody detection is often used when the live animal contains too little virus for convenient sampling of its blood or faeces.

For example feline immunodefiency virus and feline infectious peritonitis virus involve looking for antibody in blood by an ELISA.

Antibody detection is also used to determine whether an animal has produced antibody to a particular virus between disease and recovery 2 weeks later e.g. paired antibody samples from a coughing horse with equine herpes or influenza.