Spillover infection, also known as pathogen spillover and spillover event, occurs when a reservoir population with a high pathogen prevalence comes into contact with a novel host population. The infection is transmitted from the reservoir population and may or may not be transmitted within the host population.
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Spillover zoonoses
Examples of viruses that have spilled over from animals to humans include the bat-borne viruses Ebola, Marburg, Hendra and Nipah virus. Other spillover infections include types of malaria, Q fever, hantavirus, E. coli 0157, and Legionnaires' disease. Some commentators suspect that bats infected ancient peoples with measles and mumps, and that these pathogen systems coevolved with humans.
Intraspecies spillover
Commercially bred bumblebees used to pollinate greenhouses can be reservoirs for several pollinator parasites including the protozoans Crithidia bombi, and Apicystis bombi, the Microsporidians Nosema bombi and Nosema ceranae, plus viruses such as Deformed wing virus and the tracheal mites Locustacarus buchneri. Commercial bees that escape the glasshouse environment may then infect wild bee populations. Infection may be via direct interactions between managed and wild bees or via shared flower use and contamination. One study found that half of all wild bees found near greenhouses were infected with C. bombi. Rates and incidence of infection decline dramatically the further away from the greenhouses the wild bees are located. Instances of Spillover between bumblebees are well documented across the world but particularly in Japan, North America and the United Kingdom.