Page 234 - Vessel Sanitation Program 2018 Operations Manual
P. 234
VSP 2018 Operations Manual
diagnostic yield. Rectal swabs are of little or no value in
viral detection. Specimens from at least 10 ill persons
should be collected to maximize the chance that a diagnosis
can be made. The diagnostic yield is low when specimens
from fewer than 10 persons are submitted.
3. Store specimens at 4°C (40°F). Freezing may destroy the
characteristic viral morphology that permits a diagnosis by
electron microscopy.
4. Take special care to prevent cross-CONTAMINATION of
specimens during collection and transport because new
amplification techniques are exquisitely sensitive.
13.4.5.3.2 Paired Serum Specimens for Viral Diagnosis
1. Collect acute-period serum specimens during the first
5 days of symptoms. The convalescent-period serum
specimen should be collected during the third to sixth week
after illness.
2. Collect 10 pairs from ill persons (the same persons
submitting stool specimens) and 10 pairs from well
persons. Serum specimens from adults should be 10 mL
and serum specimens from children should be 3 mL.
3. Use storage tubes containing no anticoagulant (tubes with
red tops) for collection.
4. If a centrifuge is available, centrifuge the specimen for
10 minutes and remove the serum using a pipette. If no
centrifuge is available, the blood specimens can sit in a
refrigerator until a clot has formed; remove the serum using
pipettes, as above.
5. Place the serum into an empty nunc tube, label, then
refrigerate. Do not freeze.
13.4.5.3.3 Other Specimens for Viral Diagnosis
Water, FOOD, and Environmental Samples
Viruses causing AGE are not routinely detected in water or FOOD,
but may be detectable on surfaces with environmental swabbing.
Swabbing may be completed under the guidance of VSP staff or
the CDC National Calicivirus Laboratory.
Viruses have been successfully detected in vomitus specimens.
These should be collected and sent using same methodology as for
Annex 13.4: Acute Gastroenteritis Outbreak Investigation; 181
