Effect of time at temperature on wild poliovirus titers in stool specimens

Abstract

Background: The effect of transport temperature on the viability of poliovirus in stool specimens from paralyzed cases has not been tested. Quality assurance of programmatic indicators will be necessary in the final phase of polio eradication.

Objective: To estimate the effect of time at elevated temperatures on wild poliovirus titers in stool specimens.

Methods: We exposed aliquots of pooled wild poliovirus type 1 specimens to elevated temperatures (27 °C, 31 °C, and 35 °C) for varying time periods up to 14 days. We determined the virus titer of these aliquots and created decay curves at each temperature to estimate the relationship between time at temperature and virus titer.

Results: We found significantly different slopes of decay at each temperature. The negative slopes increased as the temperature increased.

Conclusions: While poliovirus in stool remains relatively stable at moderately elevated temperature, transport at higher temperatures could impact sample integrity and virus isolation results.

Keywords: Polio; Quality assurance; Reverse cold chain; Specimen transport.

Fig. 1

Change in wild poliovirus type 1 titers in stool pools incubated for 4–28 days at 25 °C, 35 °C, and 45 °C.

Fig. 2

Change in wild poliovirus titers in 10 stool pools incubated for 0–14 days at 27 °C, 31 °C, and 35 °C.

Fig. 3

Detection of wild poliovirus type 1 (WPV1) by reverse transcription-semi-nested polymerase chain reaction in stool incubated at to elevated temperatures over time. (A). WPV1-containing stool exposed for 4–28 days at 35 °C or 45 °C, and for 28 days at 25 °C. (B). WPV1-containing stool exposed for 1–14 days at 31 °C or 35 °C, and for 14 days at 27 °C.