The two main health risks travellers to the Czech Republic face are Lyme disease and encephalitis; before travelling, it’s best to consult your doctor and check whether you need to get a vaccination or not.
The Czech Republic has a fairly comprehensive medical system, and Prague has a number of clinics that cater to English-speaking clients (you could try the American Medical Centre, Tel: 807756, or the Canadian Medical Centre, Tel: 3165519). It’s a good idea to get medical insurance done before you set off on your trip- it can make things easier if you should fall ill.
Although violent crime towards foreign tourists isn’t a problem in the Czech Republic, petty theft is- especially in Prague, where pickpockets can be a real menace. Always keep your hotel door and your suitcase locked, and keep an eye on your valuables. Don’t show off your wealth, and if you’re moving through a crowded area, keep a firm grip on your wallet. Other than that, it’s wise to make a note of the telephone numbers of the local police station and your embassy.