While the H1N1 viruses affect individuals of all ages, infection in young people is more common. Those who are middle-aged or elderly are more likely to have partial immunity due to a result of prior infection, as H1N1 viruses have been circulating in the area since about 1977. Results from a case control study identified the consumption of deli turkey meat as the primary risk factor for infection and implicated Cargill Turkey Products as a potential source. These products were produced at the company's facility in Waco, Texas, and were distributed to grocery stores, restaurants, and institutions across the United States, Iceland, and Venezuela. Listeriosis is an infection caused by eating food contaminated with the bacteria Listeria monocytogenes, and primarily affects pregnant women, newborns, and those with weakened immune systems.
Symptoms are often flu-like and can include high fever, severe headaches, nausea and neck stiffness.
Since the disease is unrecognized in elephants in their native habitats, researchers believe that the elephants contracted the infection from their handlers in either Asia or North America. It is not known whether the animals can transmit the infection to one another, or whether a human host is required for transmission. The infected patient, who was admitted for an unrelated illness and died on Dec. 12, was confirmed as having legionellosis on Dec. 15. He had been in the hospital for over two weeks, and the maximum incubation period for the infection is often ten days. The head of the Victorian Infectious Diseases Service stated that the patient most likely contracted the infection by inhaling contaminated airborne particles that were released from the cooling towers to the outside of the hospital.