WHO recommends that 70% of dogs in a population should be immunized to eliminate or prevent outbreaks of rabies. This critical percentage (pc) has been established empirically from observations on the relationship between vaccination coverage and rabies incidence in dog populations around the world. Here, by contrast, we estimate pc by using epidemic theory, together with data available from four outbreaks in urban and rural areas of the USA, Mexico, Malaysia and Indonesia. From the rate of increase of cases at the beginning of these epidemics, we obtain estimates of the basic case reproduction number of infection, R0, in the range 1.62-2.33, implying that pc lies between 39% and 57%. The errors attached to these estimates of pc suggest that the recommended coverage of 70% would prevent a major outbreak of rabies on no fewer than 96.5% of occasions.
This study evaluated rabies epidemiology in Far EastAsia. Questionnaires were sent by the OIE to Far East Asian countries and eight questionnaires were returned. Data were collected from these returns, as well as from recent publications, to gather information regarding rabies epidemiology in these countries. More than 29,000 human deaths were reported in 2006 in Far East Asia, representing more than 50% of all human rabies cases around the globe. There are only a few countries or regions from which no human rabies was reported in 2006 such as Japan, Singapore, South Korea, Malaysia, Hong Kong, and Taiwan. In many of these rabies endemic countries, the number of human rabies cases has not changed much during the past decade. The only country with a steady decline is Thailand, where the number of cases has decreased from around 200 to about 20 cases per year. The most dramatic changes were observed in China. Human rabies cases declined from around 5,000 cases per year in the 1980s to about 160 in the mid-1990s. However, these trends have since been reversed. A steady increase has been reported over the past 10 years with more than 3,200 cases reported in 2006. Although there are many factors that contribute to the epidemic or endemic nature of rabies in these countries, the single most important factor is the failure to immunize domestic dogs, which transmit rabies to humans. Dog vaccination is at or below 5% in many of these countries, and cannot stop the transmission of rabies from dogs to dogs, thus to humans. It is thus most importantforthese countries to initiate mass vaccination campaigns in dog populations in order to stop the occurrence of human rabies in Far East Asia.