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Prevention of Infection in Travelers

Today we'll talk about prevention of infection in travelers. In our clinic, we call this travel health, but it is also known by the rather fancy name of emporiatrics. We will go over general precautions to give travelers when they are about the embark upon their trips; we'll talk about immunizations that are recommended for various areas of the world; we'll talk about malaria prophylaxis and also talk about diarrhea.

Many of the diseases that we try to prophylax are arthropod-borne diseases. The reason that this is important to know is that many of these things cannot be prevented by vaccine, so it is important to give people precautions as to how to prevent bites in the first place. Arthropod-borne diseases include malaria, yellow fever, Japanese bee encephalitis, African sleeping sickness, filariasis, Chagas' disease, rickettsial diseases and dengue.

Food and water-borne diseases, which we also caution travelers about, include traveler's diarrhea, which we have already discussed fairly extensively; typhoid fever, which we have discussed to some extent; cholera; hepatitis A; fluke diseases, such as schistosomiasis and tapeworms.

Among general precautions, I advise patients to remember to take an adequate supply of prescription medications, first-aid materials, extra glasses, sunscreen, mosquito repellent, and so forth. I should say that when we give travel advice, we have a tiny little yellow paper that fits into that yellow vaccine book that is distributed by the public health which you fill in with vaccines for people who are going on travel, all of which fits nicely into a passport. This little yellow thing that we have reminds people how to do this and gives them, line by line, the precautions that we are going to go through as well as a list of first-aid materials.

I think that it is important for people who have chronic illnesses which require certain medications and for which they could conceivably be hospitalized during travel, to wear some sort of medic-alert bracelet or something of that nature and to carry medication information with them, either in their passport or in their wallet. It is important in many areas of the world to avoid uncooked food. Here, we're talking about developing countries, not necessarily Western Europe, Australia, New Zealand, Japan and Canada. In developing countries where hygiene may be less optimal, it is important to avoid uncooked foods, including salads and things of that nature that may be washed in untreated water. I always tell people that it is okay to eat uncooked fruit.

Even then, you have to be a little bit cautious, because there are some areas of the world where unscrupulous street vendors will inject fruit with untreated water in order to increase the weight. If it is sold by weight, they often times inject it so as to increase the weight. Then, of course, whether you can peel of the rind doesn't really matter, because it's full of contaminated water. So there are all types of pitfalls to be aware of. Likewise, even in other settings, it is important to avoid untreated water. It is okay to drink beer, wine, anything that is canned or bottled. Boiled water, of course, is okay. If you have a choice between carbonated water and uncarbonated water, it's better to choose carbonated water, because the carbonation lowers the pH and is an added safety factor in preventing disease. You can take along tincture of iodine and add five to ten drops, or tetraglycine hydroperiodide tablets, which you can buy at camping good stores, but the caveat here is that those preparations may not kill protozoans; in other words, they may not get amoeba, giardia, etc., but they will get E. coli and other enterics that may be contaminating the water.

In many areas of the world, it is important not to swim in fresh water. Chlorinated water is okay and sea water is okay, but fresh water, such as occurs in lakes and streams, may be infested with parasites that can attack through the skin, such as certain forms of schistosomes and so forth, which can invade through intact skin. Likewise, bathing water should be heated to 122 degrees Fahrenheit. Actually, you can buy little water thermometers. In fact, I saw them last night at a fancy camping goods store that had little water thermometers that you can take with you if you want to be precise enough to actually heat your water to 122 degrees.

HIV infection is certainly reported worldwide at this point, so it is important for travelers to remember that just as they should do at home, they should avoid casual sexual contact and the potential need for injection should also be avoided, as should transfusion if medically justifiable. The latter two sound like rather crazy situations , but in the last few years, my policy regarding giving cholera vaccine has liberalized substantially.

Other general precautions to consider are prevention of motion sickness, and there are a number of preparations available, including meclizine, cyclizine, dimenhydrinate and so forth. There are also a number of sort of alternative therapies that some people feel work as well. Likewise, the scopolamine patch, which is not on there because it had been discontinued.

Altitude sickness is an important thing to consider in people who are traveling, for example, to the high altitudes in Peru or the Himalayas, Nepal, that kind of place. If you are going to be ascending rather suddenly as opposed to gradually, acetazolamide 250 mg q.8 to 10 hours for two to three days before the ascent is helpful in preventing that disease and is very well tolerated.

A polio one time single booster of either OPV or EIPV is recommended by some authorities for adults who are traveling abroad. The reason for this is sort of a lack of data. We don't really know how long vaccine-generated polio immunity lasts, so based on that lack of data, it is recommended that adults who are traveling to areas of the world where polio is still endemic.

Typhoid vaccine is recommended for travel to areas of the world where typhoid is endemic, which generally means Asia, some areas of Africa, some areas of South America, and this vaccine is generally recommended only when exposure to potentially contaminated food or water cannot be avoided.

I want to call to your attention that this is an injectable vaccine, but it is a new vaccine. The old typhoid vaccine, which I think is no longer in production, was a horrible vaccine which gave lots of people febrile illness for a couple of days and a whopping sore arm and so forth. This is the one that a lot of people got in the military years ago that made them very sick. The old vaccine is the one that made people very sick. This is a brand new vaccine that is five or seven years old and is very well tolerated.

Other commonly recommended vaccines, under some circumstances, are yellow fever vaccine. You have a map in your syllabus and I'll show a map in a few minutes of areas in the world where yellow fever is endemic. Yellow fever vaccine is a live virus vaccine, so again you have to be a little bit cautious about the timing if you are giving a series of vaccines. It is recommended for travel to countries that require the vaccine or rural areas in some parts of Africa and Central and South America.

Concomitant cholera vaccine reduces response. This is one situation where you do have to be a little cautious about the timing of vaccine, even though the cholera vaccine is a killed vaccine. So for yellow fever and cholera, think about giving those together. All other vaccines can be given at the same time.

Hepatitis A vaccine we have already discussed extensively. Hepatitis A is endemic throughout Asia, South America and Africa, so vaccine should be considered for those who are traveling there. As we discussed the other day, a single dose will be effective for somebody who is traveling within the next six months or so, but you can consolidate the immunity.

There are a number of vaccines that are occasionally recommended under some circumstances, depending on the traveler's itinerary and what they are going to be doing during the course of travel. Cholera vaccine, as I have already alluded to, is sometimes required, and although the cholera vaccine is ideally given as a series of two doses.

Meningococcal disease is endemic in some areas of the world, such as sub-Saharan Africa from December through June. It is also epidemic in certain areas of India and Nepal. It tends to occur in Saudi, Arabia during the time of their annual pilgrimage to Mecca. I believe Saudi officials require meningococcal vaccine for people who are going on the pilgrimage. It is recommended for travel to New Delhi, Nepal and certainly Saudi, Arabia. Some people recommend it also for travel to sub-Saharan Africa from December through June. Those recommendations have loosened up a bit in the last few years.

Other occasionally recommend vaccinations include hepatitis B vaccine. In general, remember that hepatitis B is spread either parenterally or sexually, so we don't usually recommend this vaccine. There are certain high-risk travelers who would certainly benefit from it, for example, health care workers who are going to be practicing in areas where this disease is endemic should have hepatitis B vaccine. It is also felt that long-term travelers, particularly small children who are going to be spending years in other areas, for example, people in the diplomatic service and so forth, should consider getting the vaccine.

Rabies vaccine is one that we don't usually recommend for most travelers, but once again, there are certain high-risk travelers in whom rabies vaccine should be considered and would be justifiable. For example, this group would include veterinarians, animal handlers, people who explore caves, because of the bat infestation of caves and the fact that bats frequently carry rabies. The areas of high indemnicity for rabies are parts of Central and South America, Asia and Africa.

Plague vaccine is occasionally recommended for high-risk travelers to rural areas, usually to Vietnam, where both epizootic and enzootic disease occur and again, for certain high-risk people who are going to be camping in areas where plague is endemic. The difficulty here, however, is that the vaccine is very difficult to get.

Japanese bee encephalitis is a disease that gained attention in the United States about 15 years ago when the son of a senator, I believe, was traveling in Central Asia and acquired this disease. Unfortunately, I believe he actually died of the disease. It is a form of mosquito-borne encephalitis that is very common in Asia, particularly in the southern parts of Asia, Malaysia and so forth. Like many forms of encephalitis, it is actually acquired by large portions of the population and discovered in studies to be very prevalent and therefore, usually in most people is subclinical, but occasionally it causes clinical disease.

On the topic of malaria prophylaxis, as I alluded to earlier, there are some general protective measures that people should take, because this is a mosquito-borne illness. Malaria prophylaxis, like many things in this world, is not one-hundred percent effective. Apart from that, we saw that there are a whole bunch of other mosquito-borne illnesses, arthropod-borne illnesses - for which we have no preventive measures except to prevent the bite. So it is important to eduate travelers about what the high-risk exposures are - rural areas and night-time exposure.

If you put on one-hundred percent DEET, you may not have to reapply for 24 hours, but on the other hand, the concentration is so high that toxicity has been associated with it, particularly in small children, in the form of neurotoxicity. If you use thirty percent DEET, that is very effective and not toxic. You have to apply it three or four times a day, but I think it is a good intermediate strength with efficacy and low toxicity.