Lyme Disease Microbiology - Epidemiology

Epidemiology

Lyme disease is most endemic in Northern Hemisphere temperate regions. However, sporadic cases of Lyme disease have been described in other areas of the world.

The number of reported cases of the borreliosis have been increasing, as are endemic regions in North America. Of cases reported to the United States Centers for Disease Control and Prevention (CDC), the rate of Lyme disease infection is 7.9 cases for every 100,000 persons. In the ten states where Lyme disease is most common, the average was 31.6 cases for every 100,000 persons for the year 2005. Although Lyme disease has now been reported in 49 of 50 states in the U.S (all but Hawaii), about 99% of all reported cases are confined to just five geographic areas (New England, Mid-Atlantic, East-North Central, South Atlantic, and West North-Central).

In Europe, cases of B. burgdorferi sensu lato-infected ticks are found predominantly in Norway, Netherlands, Germany, France, Italy, Slovenia, and Poland, but have been isolated in almost every country on the continent. Lyme disease statistics for Europe can be found at Eurosurveillance website.

Borrelia burgdorferi sensu lato-infested ticks are being found more frequently in Japan, as well as in northwest China and far eastern Russia. Borrelia has been isolated in Mongolia as well.

In South America, tick-borne disease recognition and occurrence is rising. Ticks carrying B. burgdorferi sensu lato, as well as canine and human tick-borne disease, have been reported widely in Brazil, but the subspecies of Borrelia has not yet been defined. The first reported case of Lyme disease in Brazil was made in 1993 in Sao Paulo. Borrelia burgdorferi sensu stricto antigens in patients have been identified in Colombia and in Bolivia.

In Northern Africa, Borrelia burgdorferi sensu lato has been identified in Morocco, Algeria, Egypt and Tunisia.

In Western Africa and sub-Saharan Africa, tick-borne relapsing fever has been recognized for over a century, since it was first isolated by the British physicians Joseph Dutton and John Todd in 1905. Borrelia in the manifestation of Lyme disease in this region is presently unknown, but evidence indicates the disease may occur in humans in sub-Saharan Africa. The abundance of hosts and tick vectors would favor the establishment of the infection in Africa. In East Africa two cases of Lyme disease have been reported in Kenya.

In Australia, there is no definitive evidence for the existence of B. burgdorferi or for any other tick-borne spirochete that may be responsible for a local syndrome being reported as Lyme disease. Cases of neuroborreliosis have been documented in Australia, but are often ascribed to travel to other continents. The existence of Lyme disease in Australia is controversial.