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en español
Viral
Isolation
Specimens
for measles virus isolation
It is recommended that clinical samples (10-50 ml of urine; throat or
nasopharyngeal swabs or nasal aspirates) for measles virus isolation be
collected as soon after rash as possible. The sample should be collected
at the first contact with a suspected case of measles when the serum sample
for diagnosis is drawn. Measles virus isolation is most successful when
samples are collected the first day of rash through the 3 days following
onset of rash; however, virus is still present at least through day 7
following rash.
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Guidelines
for preserving samples for measles virus isolation |
| Measles
virus is sensitive to heat, and infectivity decreases markedly when
samples are not kept cold. It is important to transport samples with
cold packs as soon as possible following sample collection. |
Urine
samples
Measles virus is present in acute cases of measles in the cells that have
been sloughed off in the urinary tract. First-voided morning urine usually
contains the highest concentration of these cells. Virus can be present
in the urine even a few days before rash appears and begins to diminish
a few days following rash.
For optimal virus preservation, centrifuge the urine sample and resuspend
the sediment in 2-3 ml of sterile transport medium, tissue culture medium
or phosphate-buffered saline and then hold at -70 C. Otherwise, keep the
urine sample at 4 C and ship on cold packs as soon as possible to a laboratory
that is able to perform viral isolation. Do not freeze large volumes (>5
ml) of urine that have not been centrifuged- just keep them cold.
Respiratory
samples
For throat or nasal washes or swabs that are in very little fluid (1-4ml),
the entire sample can be frozen at -70 C (but not dry; if needed add 2-
3 ml of the fluid mentioned above and rinse/ream swab to collect cells)
or if low temperature freezers are not available, keep the sample at 4
C until shipment. Avoid repeat
freeze-thaw cycles or freezing at -20 C (standard freezer temp) because
ice crystals can kill the virus. If -40 C or -70 C storage is not available,
it is recommended to keep the sample in the refrigerator (4 C).
See the measles lab manual for additional information
on specimens for measles. |
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