Although this paper provides information on the quantity and quality of systematic reviews on the effectiveness of public health interventions, there are a few limitations, including the lack of information regarding visitors to the Health Evidence registry. While the majority of visitors access the registry from various internet service providers, we are unable to determine their organization and the relevance of the registry content to a particular organization. Additionally, it is unclear at this time whether visitors and registered users are using reviews housed in the registry to inform their practice decisions. Studies are ongoing to evaluate the registry's usefulness and effectiveness. Inhibition of Interferon Induction and Action by the Nairovirus Nairobi Sheep Disease Virus/Ganjam Virus The Nairoviruses are an important group of tick-borne viruses that includes pathogens of man (Crimean Congo hemorrhagic fever virus) and livestock animals (Dugbe virus, Nairobi sheep disease virus (NSDV)). NSDV is found in large parts of East Africa and the Indian subcontinent (where it is known as Ganjam virus). We have investigated the ability of NSDV to antagonise the induction and actions of interferon. Both pathogenic and apathogenic isolates could actively inhibit the induction of type 1 interferon, and also blocked the signalling pathways of both type 1 and type 2 interferons. Using transient expression of viral proteins or sections of viral proteins, these activities all mapped to the ovarian tumour-like protease domain (OTU) found in the viral RNA polymerase. Virus infection, or expression of this OTU domain in transfected cells, led to a great reduction in the incorporation of ubiquitin or ISG15 protein into host cell proteins. Point mutations in the OTU that inhibited the protease activity also prevented it from antagonising interferon induction and action. Interestingly, a mutation at a peripheral site, which had little apparent effect on the ability of the OTU to inhibit ubiquitination and ISG15ylation, removed the ability of the OTU to block the induction of type 1 and the action of type 2 interferons, but had a lesser effect on the ability to block type 1 interferon action, suggesting that targets other than ubiquitin and ISG15 may be involved in the actions of the viral OTU. Nairobi sheep disease virus (NSDV) is a member of the genus Nairovirus within the family Bunyaviridae and causes acute hemorrhagic gastroenteritis in sheep and goats, with very high morbidity and mortality rates in susceptible animals [1] . It was originally isolated in Nairobi, Kenya in 1910 by inoculation of sheep with the blood of sheep suffering from acute gastroenteritis. NSDV was originally thought to be endemic only in East Africa; recent sequence data showed that the same virus can also be found in many places in India and Sri Lanka where it is called Ganjam virus (GV) [2] . Daubney and Hudson showed that NSDV is primarily transmitted in East Africa by the hard tick Rhipicephalus appendiculatus, and that animals that were bred in areas where this tick was prevalent were immune, but animals that were moved into such areas died in large numbers [3, 4] . The virus is therefore only of limited effect on stable populations, but can be a severe limitation on trade or attempts to improve stocks through introduction of new animals. There is no current vaccine. In India, the virus is found in a number of tick species, primarily Hemaphysalis intermedia [5] . Sheep and goats are the only known vertebrate hosts of NSDV/GV [6, 7] , although one or two cases of human infection through needle-stick injury have been reported as leading to mild febrile illness [8, 9] .