Molecular Epidemiology of Rabies in Southern People’s Republic of China

In recent years, the number of human rabies cases in the People's Republic of China has increased during severe epidemics in 3 southern provinces (Guizhou, Guangxi, and Hunan).To analyze the causes of the high incidence of human rabies in this region, during 2005-2007, we collected 2,887 brain specimens from apparently healthy domestic dogs used for meat consumption in restaurants, 4 specimens from suspected rabid dogs, and 3 from humans with rabies in the 3 provinces.Partial nucleoprotein gene sequences were obtained from rabies-positive specimens.Phylogenetic relationships and distribution of viruses were determined.We infer that the spread of rabies viruses from high-incidence regions, particularly by long-distance movement or transprovincial translocation of dogs caused by human-related activities, may be 1 cause of the recent massive human rabies epidemics in southern China. R abies has been endemic to the People's Republic ofChina for many years; domestic dogs act as the main reservoir (1-3).After efforts to stabilize the dog population, the lowest incidence of human rabies (159 cases) was recorded in 1996.Subsequent annual increases followed: 505 cases were reported in 2000, 1,191 cases in 2002, and 2,651 cases in 2004 (2,4).In 2005, three southern provinces (Guizhou, Guangxi, and Hunan) recorded most of the human rabies cases throughout China (5).During the next 2 years, this region had ≈50% (6,595) of the total number of cases in China and contributed to one of the most serious human rabies epidemics in this country (5,6).Various studies have been conducted to determine the causes and characteristics of rabies epidemics in China.Descriptive epidemiologic analysis showed that the increase in domestic dog populations and low vaccination coverage have contributed to rabies epidemics in the 3 provinces in southern China (7-9).Other authors have suggested that this trend may be caused by a carrier state in healthy dogs that remains undetected (10).Molecular epidemiologic analysis of dog specimens collected from 5 provinces (Guangxi, Hunan, Guizhou, Jiangsu, and Henan) demonstrated that rabies viruses (RABVs) in China are similar to those reported from previous epidemics (11).However, no studies have investigated the phylogenetic relationships among viruses circulating in different provinces during peaks of rabies incidence.RABV is the prototype member of the family Rhabdoviridae and the genus Lyssavirus.It encodes 5 structural proteins: nucleoprotein, phosphoprotein, matrix protein, glycoprotein, and RNA-dependent RNA polymerase (12).The nucleoprotein (N) gene has been extensively used for genetic typing and evolutionary studies because of its relatively conserved variation among reservoir-associated variants and geographic lineages (13-16).Since the onset of a human rabies epidemic in China in 2005, we have collected brain specimens from dogs and human patients.Partial N gene sequences were obtained in an attempt to understand the sustained increase in rabies cases in China by analysis of RABVs circulating in the 3 southern provinces with the highest rabies incidence.