Getting the right immunizations before traveling is perhaps the most important part of trip preperation. Not taking basic precautions and not getting the corrent immunizations can result in sever illness, having to terminate your trip, and often fatalities. I'll discuss what diseases are common around world, which ones apply to you, and what you should do to avoid them.

Diseases like Hepatitis, Malaria and Typhoid are common in many countries around the world. These, and many other diseases, are common in the major travel hotspots, such as south east Asia and south America. If traveling to these countries you must get proper vaccines before you leave home. Many vaccines require a course, often lasting 4 weeks, so get a proper medical consultation at least 2 months before you plan to leave.

Vaccines required by region

Diseases

Hepatits B

Hepatitis B is a DNA virus that causes liver cell destruction. It is spread through 'blood to blood' contact, including sexual intercourse, mother to new born baby, injuries, blood tranfusions, medical instruments, dental, acupuncture and other body piercing procedures, sharing intra-venous needles and reusing of razors.

Hepatits B is high infectious. It is highly epidemic in Southeast Asia, Pacific regions and West Africa. It is also common in South and Central America, the Indian subcontinent and the Middle East. It is also present, but rare in Europe, Australia and North Amercia, although generaly only amongst indigenous populations.

There is no cure for Hepatitus B. Those infected generally die of liver failure. Prevention is typically by a course of injections, lasting 4 weeks.

Japanese B encephalitis

Japanese B encephalitis is a flavivirus infection. There are many symptoms, the worst being cranial nerve paralysis. Sufferes are often left with disabilities. It is transmitted to humans by the bite of an infected Culcine mosquito that normally breeds in rice paddies. Pigs, birds and ther animals often carry the infection.

Risk is highest after rains and floods and occurs in central and Southeas Asia.

This is no cure for Japanese B encephalitis. Prevention is typically bu a course of injections, last 4 weeks. Most courses require you to not travel 10 days after the course has finsihed, as some people become unwell and required immediate medical attention.

Rabies

Rabies is a virus and is almost always fatal. Rabies is a diseas of domestic and wild animals, found mainly in, but not just dogs. It is transmitted by being bitten by a infected animal.

Rabies is found everywhere, although some islands (e.g. GB) have strict policies resulting in zero cases.

The Rabies vacination offers a short period of time (0 - 24 hours) in which, after a bite, medical help can be sought to prevent the virus taking affect.   If you are bitten by an animal saliva should be thoroughly washed off with soap and water and the wound irrigated with iodine solution or alcohol. This is very effective in removing the virus from the bitten area, providing the treatment is prompt and thorough.

Once someone has been infected with Rabies, there is no treatment.  Most suffers spend their lives in intensive care.

Pre-trip immunization is essential when traveling. 
Here is a guide to which jabs you need, and how much they cost.