Depends on which test you use.  The in-house ELISA (enzyme-linked
immunosorbent assay) Snap test can detect *circulating* FeLV antigen in
about 2-4 weeks or less. However,  a positive ELISA Snap result cannot
differentiate a transient infection from a persistent infection or predict
if the cat will become persistently infected.   IOW, a positive ELISA Snap
*does not* mean your cat is infected for life.  Most healthy cats over 4
months clear the virus in 4-8 weeks after exposure. All ELISA positives
should be confirmed by the IFA. About 40-50% of ELISA-positive cats *are
not* persistently infected. So, don't kill or get rid of your cat because of
an ELISA positive result.

The IFA (immunofluorescent antibody) assay detects FeLV antigen in the
leukocytes and platelets. A positive result indicates a productive infection
in the bone marrow cells- which usually means the cat will be infected for
life.  It usually takes about 4 weeks for bone marrow cells to become
infected- but could take as long as 12. Most IFA-positive cats are
persistently infected for life-- but could still have a good quality of life
for several years.  I had an FeLV cat that lived a good quality of life for

Effective transmission requires prolonged, intimate contact or a bite wound
from an infected cat.  Passing contact usually ain't gonna do it.

Its also possible for a cat to test ELISA positive and IFA negative. This
could mean the cat is transiently infected and is in process of clearing the
virus- or the cat is in the process of developing a persistent infection, or
the cat is harboring the virus in some *non-myeloid* compartment in the
body.

For FIV- it usually takes about 8 -12 weeks for antibodies to develop after
the initial infection. Kittens <6-8 months old can test positive for FIV
from receiving FIV antibodies from their mother through colostrum *without*
being infected. An FIV-vaccinated cat will also test positive as well as her
kittens. There's only one DNA test that can differentiate FIV-vaccinated
cats from FIV-infected cats and its only available at UC-Davis.

Effective transmission usually requires a bite wound. Normal contact ain't
gonna do it. With good care, FIV cats can live near normal lifespans.

Best of luck,

Phil