Rates of tick-borne infections in the United States have been increasing dramatically since 2000. See attached graph (Lyme disease displayed as cases/100,000 to allow fit). Although this phenomenon might reflect changes in human population density and artifacts of reporting and diagnosis, I suspect that these data are related to increasing tick and animal reservoir populations.

Update: Also referenced in ProMED

As America once again enters the “Lyme disease season” information regarding this major infectious disease continues to evolve rapidly. The following material has been generated using GIDEON, an interactive on line program that can be used to diagnose or explore the status of all infectious diseases: signs and symptoms, status in every country, ongoing epidemics, antibiotics, vaccines, parasites, virus … in real time. So, let’s test your knowledge about Lyme disease:

1. True or false: Lyme disease is a relatively new infection that is primarily limited to the United States.
2. You have probably heard that Lyme disease is transmitted by ticks. How many tick-borne diseases occur in the world ? In the United States ?
3. Many other infectious diseases are characterized by severe illness, involving many body systems. Are there any truly unique features to Lyme disease ?
4. How many antibiotic agents are available ? How many are effective against the bacterium that causes Lyme disease ?

I put these four questions to GIDEON … (more…)

Steve is quoted in ProMED again:

A recent ProMED-mail posting is a reminder that Lyme disease is extremely common in the Baltic region. In fact, disease rates are several fold higher in this area than in the USA (see graph at http://exhibit.gideononline.com/Lyme-Baltic.jpg).

Additional background data abstracted from GIDEON (primary references available on request):

The 1st cases (3) of Lyme borreliosis in Lithuania were diagnosed in 1987; and Estonia reported its 1st cases in 1988.
Endemic foci exist in the western, eastern, and southern regions of Estonia. The areas of highest risk are concentrated along the Finnish Gulf coast in Harjumaa and Western Virumaa, in Parnumaa and Eastern Virumaa counties, and on the island of Saaremaa.
In Latvia, 2.7 per cent of workers in high-risk occupations and 3 per cent of healthy persons in the Karksi Nuia region (south) of Estonia are seropositive.
_Ixodes ricinus_ is abundant in Estonia, and _Ixodes persulcatus_ is found in the east and south of the country; 3 per cent of _I. ricinus_ adults and 5 per cent of the _I. persulcatus_ adults are infected with _Borrelia burgdorferi_; 31 per cent in Narva-Joesuu, 12 per cent in Western Virumaa, and 14 per cent in Tartumaa. Borreliae are found in 15 per cent of ticks (_I. ricinus_) on Vormsi Island. Tick infection by _B. afzelii_ and _B. garinii_ has also been demonstrated.
_B. afzelii_ is the dominant species among _I. ricinus_ and _I. persulcatus_ in Latvia, followed by _B. garinii_ and _B. burgdorferi_ (1993 to 2002). In Lithuania, 11 per cent of adults and 1 per cent of nymphal _I. ricinus_ ticks are infected with Borrelia (1988 to 1991).