To control for possible confounding by smoked sausage consumption, a stratified analysis was conducted using only case-patients and controls who had eaten smoked sausage. Because the usual incubation period of trichinellosis is 8-15 days, the environmental investigation focused on the meat that had been used for sausage production during the last week of September. Samples from neither the meat nor the sausages remained for investigation. Samples from later production lots were negative for trichinellosis. The trichinellosis control certificates for the fresh pork neck provided by the abattoir in Spain had control numbers that did not match the control numbers on the meat.
Further investigations are ongoing.
The findings in this report indicate the existence of two outbreaks of trichinellosis. Because the exact source of the meat from either outbreak could not be determined, it is unclear whether the outbreaks were related. The large outbreak from the smoked sausage could have heightened awareness of trichinellosis in NRW, which resulted in the identification of the small outbreak that may have been otherwise unnoticed. The 52 cases identified in these outbreaks may represent only a fraction of persons actually infected. As a result, hundreds of persons potentially were exposed.