Rabies in North America and Europe

Rabies is caused by infection with a negative-stranded RNA virus within the Lyssavirus genus (family Rhabdoviridae, order Mononegavirales), mainly transmitted via saliva following a bite from an infected animal.Transmission may also occur through mucous membranes, but not through intact skin.The main source of infection from domestic reservoir species is dogs and cats.There are seven rabies virus (RV) genotypes, six of which have similar effects in man; the exception is genotype 2, which has never been isolated in human cases.The main genotypes of interest for the purpose of this review are 1, 5 and 6.Genotype 1 viruses have a worldwide distribution and are generally found in terrestrial animals.Genotypes 5 and 6, commonly known as European bat lyssaviruses (EBLs), are restricted in distribution to Europe and are frequently isolated from European bats.Genotype 1 viruses have never been isolated from European bats.Rabies can probably infect most if not all mammals.The virus enters the central nervous system of the new host, causing an encephalomyelitis which is always fatal once symptoms develop.The manifestations in human cases include spasms, hallucinations, hydrophobia, aerophobia, dysphasia, paralysis and coma.Extreme agitation and convulsions can be interspersed with periods of lucidity.World wide, the disease causes many thousands of human deaths each year.The World Health Organization (WHO) World Survey of Rabies for the year 1997 gave an estimate of between 35 000 and 50 000 annually 1 .Gross under-reporting is likely because many countries lack the necessary diagnostic facilities; also, the populations most affected tend to be rural (especially in developing countries) with erratic noti®cation systems.African and Asian countries are particularly affected because of their animal reservoirs and the lack of healthcare and control measures.The subject has been thoroughly reviewed by King and Turner 2 .Here we focus on human rabies in North America and Europe. HUMAN RABIES North AmericaUntil recently it was dif®cult to identify which strains of RV were causing human disease.This has changed with the advent of molecular diagnostic tools such as nucleotide analysis, which also provide clues to the source of the virus.It now seems that a large proportion of human rabies infections in the United States are transmitted by bat bites.Some people when bitten ignore the danger and take no action; many are simply unaware of the biteÐperhaps because they are asleep when it happened.Also, parents may not know that their children have been in contact with bats.Since the 1900s, the number of deaths from rabies in North America has fallen from 100 or more each year to just one or two cases.Much of the decline dates from the 1940s, when vaccination and animal control programmes were set up.In the early 1940s, there were about 40 cases each year 3 .This ®gure decreased to a total of 99 for the entire decade in the 1950s, and then dropped further to 15 in the 1960s, 23 in the 1970s, 10 in the 1980s and 22 from 1990 to 1996 4 .Widespread vaccination of canine pets in the 1950s was partly responsible for the decrease in human cases in subsequent years 5 .The vaccination campaigns implemented in the 1940s all but eliminated the circulation of canine strains of genotype 1 RV by the 1960s.However, the late 1970s and early 1980s witnessed the re-emergence of a variant well adapted to dogs in south Texas 6 , thereby increasing the risk to human beings.4 human cases were reported in 1997 (Montana, Washington, Texas and New Jersey) and just 1 case in 1998 (Virginia).No human deaths were recorded in the USA for 1999 but in 2000 there were 5, reported from California, New York, Georgia, Minnesota and Wisconsin plus 1 from Quebec (Canada) 7 .The case reported from New York was in a patient who had come from Ghana after being bitten by a dog; all the others were thought to be associated with bats. EuropeHuman cases in Europe have been well documented since the late 1970s.In 1997 17 human cases were reported 8 Ð 12 from the Russian Federation, 3 from Romania, 1 from Lithuania and 1 from France (imported).In 1998 the total