He is interested in the means by which viruses evade the body’s system of defence against infection and how this impacts on the virus’ host range (what animals they infect) and pathogenicity (the severity of the disease they cause). Type I interferons, which are substances produced by virus-infected cells, comprise the host's primary (innate) line of defence against viruses. They are secreted from the infected cell and induce the expression of a diverse group of genes that create an antiviral state in neighbouring uninfected cells. To establish infections in vivo (inside the body), therefore, viruses must replicate in the face of this powerful defence mechanism.