Survival of poliovirus on soft fruit and salad vegetables.

A series of studies were performed, using poliovirus, to ascertain the potential for enteric pathogenic viruses to survive on various foodstuffs. The extraction protocols, which could be performed in just a few hours, were developed for use with quantities of food that would normally constitute a portion for consumption. The protocols were based on elution of viruses from food surfaces, followed by differential centrifugation to remove food debris and concentrate viruses. The studies were mostly performed using fresh produce stored at refrigeration temperature for 2 weeks or so, which was considered to represent the maximum time elapsing between purchase and consumption. Each food sample was inoculated with a viral suspension, and samples were analyzed immediately and at intervals throughout the experiment. Statistical analyses were performed on the results, and the decimal reduction times (D-values), or number of days after which the initial virus numbers had declined by 90%, were calculated. In summary, the resulting D-values were as follows: lettuce, 11.6 days; green onion, no decline; white cabbage, 14.2 days; fresh raspberries, no decline; and frozen strawberries, 8.4 days. The results showed that enteric viruses may persist on fresh fruit and vegetables for several days under conditions commonly used for storage in households. Therefore, if contamination has occurred before purchase, there will always be a risk of infection from consumption of the food.