ABSTRACT
AIM: The effect of cold box temperature and distance on virus titers, poliovirus isolation rate, and appearance of orphan polioviruses was investigated. METHODS: Cold boxes with stools were randomly selected and examined for internal temperature over a 7-month period. After virus isolation in Rhabdomyosarcoma (RD) cell line RDand L20B, titer calculations and intratypic differentiation were done on isolates. Sequencing and molecular studies were done on the isolates periodically in the order of arrival in the laboratory for a period of 30 months. RESULTS: Seventy-one (51.1%) boxes had the temperature range of 1 -4°C, 53 (38.1%) had 4.5 -8°C,. while 15 (10.8%) had temperature between 8.5°C and 17.0°C. Poliovirus was isolated from 24 (8.6%) specimens made up of 13 wild 1 and 2 and 11 Sabins 1, 2, 3 with titers between 10(1.8) and 10(5.4) TCID(50) /100 µl. Temperature and titer were inversely proportional and statistically significant. (r = -0.83, P < 0.05). Distance to laboratory was not significantly related (r = -0.025) to temperature when appropriate cold box temperature was maintained. Of the 18,188 acute flaccid paralysis (AFP) specimens received in the laboratory between June 2008 and December 2010, 1,752 poliovirus isolates (9.6%) consisting of 480 wild and 82 orphans were found. A positive correlation between the distance and orphan viruses (r = 0.425; P = 0.027) was observed. CONCLUSION: While poliovirus titer depends on the inside temperature of the cold box, distance to the laboratory was found to be a predisposing factor to the appearance of orphan viruses.
