In suspected polio cases, what samples are best for initial testing and why?

• A. Two stool specimens collected within 14 days of onset (ideally 24 hours apart) for virus isolation/RT-PCR.
• B. A single serum sample is sufficient.
• C. Urine samples collected after several weeks.
• D. Cerebrospinal fluid alone is sufficient.

Answer: (A)

In suspected polio, the goal is to show the virus itself, and the best evidence comes from stool because poliovirus replicates in the gut and is shed in stool early in infection. Collecting two stool specimens within 14 days of onset, ideally about 24 hours apart, maximizes the chance of detecting the virus with either virus isolation or RT-PCR. This approach catches the period of peak and intermittent shedding, giving the most sensitive initial test result.

A single serum sample won’t reliably confirm acute polio, since antibodies reflect past vaccination or infection and may not indicate an active infection at the onset. Urine collected only after several weeks is unlikely to contain detectable virus, since shedding wanes over time. Cerebrospinal fluid alone is not sufficient for initial diagnosis because the virus is not consistently present in CSF at detectable levels.