Table 1.

The Fiebig stage of primary HIV infection based on the emergence of a specific set of viral markers in the plasma of individuals who have acquired HIV. Classifications are based on a parametric Markov model

Fiebig stage	Cumulative duration		HIV RNA	P24 antigen	Antibody (EIA)		Western blot
	Days	95% confidence interval			NS	S
I	5.0	3.1–8.1	+
II	10.3	7.1–13.5	+	+
III	13.5	10.0–17.0	+	+		+
IV	19.1	15.3–22.9	+	+		+	Indeterminate
V	88.6	47.4–129.8	+	+	+	+	+ (p31 band negative)
VI	Open ended		+	+	+	+	+ (p31 band positive)

EIA: enzyme immunoassay: NS: not sensitive (refers to second generation not IgM-sensitive immunoassay); S: sensitive (refers to second generation IgM-sensitive immunoassay).