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Last summer I was bit by a tick while hiking the northern section of the Appalachian trail. I took the preventive dose of antibiotics. So far, nothing has happened. Is the danger of Lyme disease over now?

It depends on the type of tick that bit you. Not all ticks pass diseases to humans. The deer tick (I scapularis) is the one that transmits Lyme disease. The specific bacteria they carry is called Borrelia burgdorferi.

Not all deer ticks carry the bacteria. It is estimated that about 20 per cent of the tick population are infectious. And not all people who are bitten get Lyme disease. Scientists aren't sure why this happens to some, but not all, people.

Older adults or anyone with a weakened immune system may be at increased risk. Studies also show that the tick can't pass the bacteria to you (the host) until it has been attached to your skin for 36 to 48 hours. If the tick is just crawling on the skin or clothing, you are still safe from the disease.

Likewise, if the tick was attached but not engorged, your risk of disease is less. You should remain alert to any symptoms of later-stage Lyme disease. This can include severe headaches, painful joint swelling, or numbness and tingling of the fingers and toes.

Symptoms can appear for the first time years after a tick bite. It's a good idea to see your physician at least once a year for a check-up. Late-stage Lyme disease can also present with unknown cardiac (heart) problems.

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