Table 2. Stages in the HIV infection and care continuum.
Infection/care stage of transmitterDefinition
UndiagnosedTransmission intervals whose midpoint is before diagnosis:
  Confirmed to have recent infection at diagnosisAll transmission intervals of transmitters that were
confirmed to have recent infection at time of diagnosis.
  Estimated to have recent infectionConsidering transmitters that had no evidence of recent infection
at time of diagnosis, all transmission intervals whose midpoint is less
than 12 months after the estimated infection date.
  Estimated to have chronic infectionConsidering transmitters that had no evidence of recent infection
at time of diagnosis, all transmission intervals whose midpoint is
more than 12 months after the estimated infection date.
DiagnosedTransmission intervals whose midpoint is after diagnosis and before
ART start (only of transmitters that are in contact with care services):
  Diagnosed <3 months, confirmed recent
infection at diagnosis
Considering transmitters who had confirmed recent infection at time
of diagnosis, all transmission intervals whose midpoint is within the
first 3 months after diagnosis.
  No CD4 measuredNo available CD4 count since diagnosis up to the midpoint of the interval.
  CD4 >500CD4 counts remained above 500 cells/ml between the first
CD4 count and the midpoint of the interval.
  CD4 350–500CD4 counts decreased to 350–500 cells/ml between the first
CD4 count and the midpoint of the interval.
  CD4 <350CD4 counts decreased to below 350 cells/ml between the first
CD4 count and the midpoint of the interval.
ART initiatedTransmission intervals whose midpoint is after ART start (only of
transmitters that are in contact with care services):
  Before first viral suppressionNo first viral load measurement below 100 copies/ml in any
transmission interval of the transmitter after ART start
  After first viral suppression*
    No viral load measured*No viral load measurement in any transmission interval
of the transmitter after ART start
    No viral suppression*At least one viral load measurement at or above 100 copies/ml in
any transmission interval of the transmitter after ART start
    Viral suppression, one observation*One viral load measurement in any transmission interval of the
transmitter after ART start, which is below 100 copies/ml.
    Viral suppression, ≥2 observations*Several viral load measurements in any transmission interval of the
transmitter after ART start, all of which are below 100 copies/ml.
Not in contactNo patient record (last contact, clinic visit, CD4 measurement,
viral load measurement) in the past and future 9 months from
the midpoint of the transmission interval.

*Although flow through the stages is typically unidirectional, men could move freely between these stages.