Table 5.

Enzyme-linked immunosorbent assay (ELISA) interpretation for Ross River virus.

Scenario	Sample 1	IgM	IgG	Diagnosis	Comments
1	1st	Neg	Neg	Pos	A negative result from the first blood sample may be due to recent infection and IgM titre has not risen to the detectable level.
	2nd	Pos	Pos
2	1st	Pos	Neg	Pos	A detectable IgM titre, without IgG, in the first sample indicate recent infection (likely 7–10 days ago). IgM antibodies in some horses could persist for at least 5 weeks and potentially longer [25]. Therefore, detection of IgM + IgG combination may indicate previous infection, rather than recently infected.
	2nd	Neg/Pos	Pos
3	1st	Pos	Pos	Pos
	2nd	Neg/Pos	Pos
4	1st	Neg	Pos	Pos	Indicate previously infected. Not recent infection.
	2nd	Neg	Pos
5	1st	Neg	Neg	Pos	It is unlikely that the patient or horse seroconverted to IgG, without IgM, upon recent infection. Results from the first sample is possibly due to false negative result in either IgG or IgM. Therefore, inconclusive as to recent or previous infection.
	2nd	Neg	Pos
6	1st	Neg	Neg	Neg	N/A
	2nd	Neg	Neg

Ig = Immunoglobulin; Pos = Positive; Neg = Negative; N/A = Not applicable; ¹ Sample 1 and 2 should be collected at least 2–4 weeks apart.