The incidence of new cases of Lyme disease has doubled in the US since 1991, according to the US Centers for Disease Control (CDC) - from just over 9000 cases in 1991 to nearly 18,000 new cases in 2000. Children aged 5-9 years and adults aged 50-59 years are most at risk.

The incidence of Lyme is highest in the northeastern, mid-Atlantic and north-central parts of the US, with about 95 per cent of the new cases in just 12 states, including New York, New Jersey, Connecticut, Rhode Island and Delaware. The national incidence of Lyme disease is 6.3 per 100,000 but, in Connecticut, which had the highest number of new cases, it is 110.8 per 100,000.

While vaccination has been recommended for those living in high-risk areas, the CDC finds that GlaxoSmith-Kline’s vaccine LYMErix has only a 75 per cent rate of effectiveness at the three recommended doses. Booster doses may be required, but the optimal schedule for this has not yet been determined (MMWR, 2002; 51: 29-31).

* Other new data conclude that there is still no single reliable test for Lyme disease.
Although recent refinements in laboratory tests like skin biopsy and blood tests have made it easier to detect Borrelia burgdorferi in patients with erythema migrans, the characteristic bull’s-eye rash, the detection rate is low - between 40 and 80 per cent.

To be sure of a diagnosis, a combination of a skilled physician and more than one test may be necessary (Clin Infect Dis, 2001; 33: 2023-7).

Also, only 40-60 per cent of fair-skinned subjects with Lyme develop the typical rash, and it may not even show up on darker-skinned individuals or may appear
as a bruise. These cases may be overlooked by physicians, no matter how skilled.