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If you have traveled recently to a foreign destination, particularly a tropical one, and have fever, there are numerous possible causes that should be considered. The summaries below are intended to put the problem of post-travel fever into perspective and highlight those causes that require immediate attention. Please note that there are dozens of "tropical" or geographically-localized infections that are not mentioned below, but which might be considered as potential causes of fever in a returning traveler, depending on their itinerary and activities.
Most fevers (at least half) that occur in returning travelers are due to infections that might occur anywhere (e.g., respiratory viral and bacterial infection, urinary tract infection, skin infection, mononucleosis and other "viral" syndromes, toxoplasmosis, sexually-transmitted infections). These problems are the same as those that can be acquired at home, but may be more prevalent in travelers because of the invariable increased contact with others during travel. For example, the incidence of upper respiratory infections is increased after air travel.
Among the "tropical" infections in travelers, malaria is among the most common. At many destinations, bites by mosquitoes that transmit the infection are difficult to avoid, even with bednets and repellants. Most cases occur in travelers who were born overseas and travel back to visit friends and family. Because of their origin, these travelers are sometimes under the misapprehension that they are not susceptible to malaria. However, the immunity against malaria that is acquired by continuous exposure in childhood is lost after a few years living in the U.S. where there is no exposure to malaria parasites. The other group of travelers who risk developing malaria are those who do not take antimalarials preventively in a malarious area or those who are unable to complete the preventive treatment because of intolerance to the medication. Currently, there is no effective vaccine to prevent malaria. The most virulent strains of malaria found in Subsaharan Africa can be deadly to both adults and children if unrecognized and untreated. That is why it is always a good idea to evaluate a fever in a returning traveler who was exposed with a physician who is familiar with this disease.
Malaria usually begins abruptly with repeated bouts of chills, fever, and then sweats. Between episodes of fever, the infected individual may feel relatively well but exhausted. Headache and diarrhea may also be present in some individuals. Symptoms may begin up to a month after travel for the more virulent types of malaria, or up to a year in the less virulent forms of the disease. The best way to diagnose malaria is by examining blood smears, a procedure that requires some experience and proficiency. So, diagnosis at a medical center that sees malaria cases from time to time, or through a full-service travel clinic, usually results in more prompt diagnosis and treatment.
DENGUE FEVER and OTHER MOSQUITO-BORNE VIRUSES
Dengue fever is a common viral infection that is transmitted by mosquito bites. Travelers are more likely to acquire dengue in Central America, the Caribbean, or Southern Asia than in Africa or South America. Dengue infection features fever, malaise, and severe muscle and joint pains. The illness lasts for approximately one week, and most patients survive. Reinfections with dengue viruses of different types can be very severe and feature hemorrhages or shock. This form of the disease is very rare in travelers. There is a vaccine against dengue on the horizon, but it is not yet fully studied and is not available at this time. The best prevention is avoidance of mosquito bites.
Recently, other mosquito-borne viruses have emerged and could present a problem for travelers. these include Chikungunya in the Indian Ocean countries and Rift Valley fever in Eastern Africa.
Typhoid is very uncommon in most tourists but can occur in long-term resident of countries with poor sanitation or in adventure travelers. It is usually acquired in food contaminated by a food-handler who is a carrier or from untreated water that has been contaminated with human waste. The onset of fever is more insidious than malaria and affected individuals may also have abdominal pain, constipation, diarrhea, cough or rash. The untreated infection usually lasts for about 3 weeks and can be severely debilitating or result in serious complications.
The typhoid vaccines work as a preventive, but it is not 100% effective. So, consuming a heavily contaminated food or drink can overcome the protective effect of the vaccine. Typhoid fever may be difficult to diagnose, even for physicians familiar with the disease. Certain antibiotics are effective in eliminating the germ that causes the disease and preventing complications.
Viral hepatitis A & B are extremely rare in individuals who have completed the vaccine series to prevent these infections. Prior to the development of the hepatitis A vaccine, this form of viral hepatitis was by far the most common acquired by travelers, almost always in contaminated food or water. A single dose of hepatitis A vaccine is protective for relatively short trips, but a second, booster injection is required to assure life-long immunity against this infection. Solid immunity to hepatitis B, which is usually acquired as a bloodborne or sexually-transmitted disease, requires a series of 3 injections. In our travel clinic, we uniformly advise both immunizations (or a combined vaccine) to protect against acquisition of hepatitis A from contaminated foods or hepatitis B from emergency medical care. There are other forms of hepatitis for which we do not have vaccines -- like hepatitis A, hepatitis E is also foodborne. Hepatitis C, like hepatitis B, is also bloodborne.
Viral hepatitis is usually associated with malaise and a loss of appetite. Symptoms may also include fever, abdominal discomfort under the right lower ribs, dark urine, or jaundice (yellowing of the whites of the eyes).
These infections are acquired by bites of ticks, chiggers, or other insects. Therefore they occur primarily in hikers, campers, hunters, or other adventure travelers. Rickettsial infections that occur in these travelers include African tick fever (from Southern Africa) and scrub typhus (from Southeast Asia). They are not fatal infections and can be treated with certain antibiotics.
EBOLA and OTHER HEMORRHAGIC VIRUS INFECTIONS
Infections that make the international news, such as Ebola, Marburg, Lassa fever and others, are rare even in the countries in which they episodically occur. Although we have no vaccines or other preventive measures to apply against these viruses, these infections have been exceedingly rare among U.S. travelers or tourists in the past. Outbreaks are rare even in the countries that harbor these diseases. If an outbreak occurs in a country in which you are traveling, it would be wise to obtain as much information on the location of cases and to avoid the epidemic area. Our clinic would be happy to help with specific advice on this matter should the need arise.