Most really dangerous diseases have been all but eliminated in developed countries. But when you travel in some third world countries, exposure to these diseases is a real threat. If you will be traveling in underdeveloped countries, it is a good idea to look into the assortment of shots that you may need for immunizations. Hepatitis A, hepatitis B, cholera, typhoid, malaria and rabies are just some of the 'nasties' that you will want to be protected from.

The principle behind a vaccine or immunization is to expose your body's system to the disease after it has been rendered harmless. By doing so, the body can build up its own natural protection so that if it encounters the virus, the body will be "immune" to its effects. This immunization effect takes time, so it is a good idea to give your body at least a month head start to condition itself before getting on the plane or boat. Another reason to begin your immunization program early is that many of the programs require a series of shots over several weeks or months. As well, some vaccinations cannot be administered at the same time. Ask your physician about your immunization requirements.

Along with your passport and visa, some countries require that you have your immunization cards with you before allowing you to enter a country (if immunizations are necessary).

Immunization From What?
You may need immunization or a vaccination for the following:

  • Cholera - is spread through water. The vibrio cholera bacterium invades the intestine and releases a toxin that causes massive fluid loss through diarrhea. Patients die from dehydration. A vaccination is available but is relatively ineffective against modern strains of cholera. The disease can be treated with anti-biotics and requires hospitalisation. Basically, avoid areas with reported cholera outbreaks. In some situations it may be wise to have the cholera vaccine (ie. for the trans-Africa traveler), as travelers may be asked by immigration officials to present a certificate, even though all countries and the World Health Organization have dropped a cholera immunisation as a health requirement. You might be able to get a certificate without having the injection from a doctor or health center sympathetic to the difficulties of travel in Africa. Check out this list of Cholera-infected countries.
  • Dengue -  a mosquito born virus that has no treatment or vaccination. Basically it causes very painfull muscle spasms and cramps.
  • Diphtheria - caused by a bacillus bacteria that invades tissues in the upper respiratory tract and releases toxins that are potentially fatal. Diphtheria may be treated or vaccinated against. After an initial course of three injections, boosters are necessary every 10 years.
  • Encephalitis - an infection of the brain, often caused by viruses transmitted by ticks or mosquitoes. Vaccines are available for Japanese encephalitis and the tick-born encephalitis found in Asia. Encephalitus is not of great risk to travelers. Consider the vaccination if spending a month or longer in a high risk area, making repeated trips to a risk area or visiting during an epidemic. It involves three injections over 30 days. The vaccine is expensive and has been associated with serious allergic reactions so the decision to have it should be balanced against the risk of contracting the illness.
  • Hepatitis A - the most common travel-acquired illness after diarrhea which can put you out of action for weeks. Hepatitis A is not life threatening, but unpleasant, and is transmissible by food and water. Havrix is a vaccination which provides long term immunity (possibly more than 10 years) after an initial injection and a booster at six to 12 months. Gamma globulin is not a vaccination but is ready-made antibody collected from blood donations. It should be given close to departure because, depending on the dose, it only protects for two to six months.
  • Hepatitis B - transmissible by contact with body fluids (such as blood and through sexual contact). Hepatitis B is said to be 100 times more transmissible than HIV/AIDS. Hepatitis B and C will eventually kill you. Travelers who should consider a hepatitis B vaccination include those visiting countries where there are known to be many carriers, where blood transfusions may not be adequately screened or where sexual contact is a possibility. It involves three injections, the quickest course being over three weeks with a booster at 12 months.
  • Meninogococcal Meningitis - an infection of the lining of the brain and may be fatal (you can die from it within a few hours). It is spread by inhaling droplets of sputum that some one may cough or sneeze up. Even healthy people carry this disease. Vaccinations are available for some forms of meningitis.There are many carriers and vaccination is recommended for travelers to certain parts of Asia, India, Africa and South America. A single injection will give good protection for three years. The vaccine is not recommended for children under two years because they do not develop satisfactory immunity from it.
  • Polio - an infection of the central nervous system that results in paralysis. It is untreatable but a vaccine is available Polio is a serious, easily transmitted disease, still prevalent in many developing countries. A booster every 10 years maintains immunity.
  • Rabies - Vaccination should be considered by those who will spend a month or longer in a country where rabies is common, especially if they are cycling, handling animals, caving, travelling to remote areas. The rabies vaccination involves three injections over 21 to 28 days. If someone who has been vaccinated is bitten or scratched by an animal they will require two booster injections of vaccine (those not vaccinated require more).
  • Tetanus - a potentially fatal disease caused by a clostridium bacteria that enters the body through a wound, causing muscle spasms, etc. Tetanus is difficult to treat and can be fatal but a vaccine is available. Everyone should have this vaccination. After an initial course of three injections, boosters are necessary every 10 years.
  • Tuberculosis - a bacillus bacteria that is on the rise across the world although the risk to travelers is usually very low. It is difficult to treat, and may require patient isolation, and can be particularly dangerous when it infects the respiratory system. For those who will be living with or closely associated with local people in high risk areas such as Asia, Africa and some parts of the Americas and Pacific, there may be some risk. As most healthy adults do not develop symptoms, a skin test before and after travel to determine whether exposure has occurred may be considered.
  • Typhoid - an infection caused by a Salmonella bacterium that may spread through food or water (this is an important vaccination to have where hygiene is a problem). Typhoid causes severe fevers, etc. but infections may be treated and vaccines are available (either as an injection or oral capsules).
  • Yellow Fever - now the only vaccine which is a legal requirement for entry into many countries, usually only enforced when coming from an infected area. Protection is recommended where the disease is endemic (ie. Africa and South America). You usually have to go to a special yellow fever vaccination center. This vaccine lasts 10 years. Check out this list of Yellow Fever-infected countries.