By: Keith Rosenbach, MD, PhD, Jason Sniffen, DO, and Jeffrey P. Nadler, MD, FACP
If you visit American city,
You will find it very pretty.
Just two things of which you must beware:
Don't drink the water and don't breathe the air!
--- Tom Leher, Pollution
There are approximately 1 billion airline trips per year, and nearly 50 million involve travelers from industrialized countries to underdeveloped nations, according to Dr. Ed T. Ryan of the Tropical and Geographic Medicine Center, Massachusetts General Hospital and Harvard Medical School, Boston.[1,2] Approximately 20% to 70% of these travelers will develop illness, and 1% to 5% will seek medical attention. Death from illness acquired abroad is rare, and infectious diseases account for only 1% to 4% of travel deaths. The vast majority of travel deaths are due to trauma and cardiovascular illness.
Nevertheless, more than half of these travelers will suffer some kind of illness that will claim 3 of their average 14 days of travel.
Risk factors for travel-related infection include the traveler's underlying medical condition, activities, length of stay, and location. Major problems encountered include traveler's diarrhea, respiratory infections, arthropod-borne diseases, sexually transmitted diseases (STDs), animal bites, exposure to fresh and salt water, and blood-borne infections from IV drug abuse and transfusions. Travelers should carry a medical kit, including antibiotics. Other conditions the traveler may develop, related to the traveling itself, include jet lag, motion sickness, trauma, and deep vein thromboses. What to Do Before You Go: Immunize!
Considerations With Live Vaccines
Live viral vaccines should be avoided in pregnant women. If the female traveler is vaccinated with live vaccines, she should be advised to avoid pregnancy for 3 months. For the varicella vaccine, pregnancy should be avoided for 1 month. There are no contraindications to the live viral vaccines in women who are breastfeeding, including the measles-mumps-rubella (MMR) vaccine.
Live viral vaccines should also be avoided in immunosuppressed patients. The exception is the MMR vaccine, which is not contraindicated in HIV-infected patients. Also, there is concern about the live oral polio (OPV) and varicella vaccines in the household contacts of immunosuppressed patients.
For travelers currently on antibiotics, the oral typhoid vaccine is contraindicated. The antibiotic may kill the vaccine strain, rendering the vaccine ineffective. There are no contraindications to live viral vaccines for travelers with a history of seizures. Those who have developed vaccine-associated Guillain-Barré syndrome should avoid that specific vaccine.
Live viral vaccines, including yellow fever, MMR, influenza, and varicella vaccines, should not be given with blood products, especially intravenous immune globulin (IVIG). The antibodies in the blood products may interfere with the development of an active immune response to the vaccine virus. If possible, the vaccine should be given 2 weeks prior to blood product administration.
Egg Allergies and Vaccines
Travelers with an allergy to eggs will be concerned about specific vaccines. Influenza, yellow fever, and the purified chick embryo cell (PCEC) rabies vaccine viruses are produced in chicken eggs, whereas MMR and the other 2 rabies vaccines are not grown in chicken eggs. It is important to determine the nature of the egg allergy. If the traveler experienced gastrointestinal (GI) upset, this is unlikely to be a true allergy, and one can proceed with vaccination. If the allergic reaction is severe, such as anaphylaxis, the patient can be desensitized and then vaccinated.
Don't Miss a Vaccine Opportunity
An appointment at the travel clinic is a good opportunity to get the patient up-to-date on routine vaccinations, which are targeted at specific populations: MMR, diphtheria and tetanus toxoids and pertussis (DTP), HiB, varicella, hepatitis B virus (HBV), and oral poliomyelitis vaccine/inactivated poliomyelitis vaccine (OPV/IPV) in children, and pneumococcal and influenza vaccines in the elderly and in patients with chronic diseases. HBV vaccine should also be offered to sexually active adolescents and adults. Since polio has been eradicated in the Western Hemisphere, a polio vaccine booster should be offered to adults traveling to Asia and Africa. MMR vaccine should be given to any traveler born after 1957 unless there is documentation of 2 vaccinations with the live measles vaccine or the traveler has positive antibody titers. Adult tetanus vaccine (Td) should be updated every 10 years. To accommodate the child traveler, many of the vaccines can be given in an accelerated series. (For further information about immunizing children, see "Advice for Families Traveling With Young Children"
[http://www.medscape.com/SCP/IIM/1995/v12.n10/m1408.steele/m1408.steele.html] and "Management of Missionaries and Their Families"
[http://www.medscape.com/SCP/IIM/1999/v16.n10/m6472.stee/m6472.stee-01.html].)
Specific Vaccine Indications
Yellow fever is present in Africa, Asia, and South America. Thus, any traveler to a developing country will require the yellow fever vaccine. The vaccine contains a live attenuated virus. It is administered 10 days prior to travel, requires only 1 dose and a booster after 10 years, and can be given to children older than 9 months. The vaccine is contraindicated in pregnant women, immunosuppressed patients, and travelers younger than 9 months.
The meningococcal vaccine that is available in the United States is a quadrivalent vaccine covering types A, C, Y, and W-135. The vaccine is required in travelers to Africa in the dry winter months. It is administered as a single dose, with a booster every 3-5 years, and can be given to travelers older than 2 years.
Travelers are at risk for hepatitis A viral (HAV) infection in Africa, Alaska, Asia, Greenland, South America, and the western half of the United States. The risk is 1:750 travelers per week. The HAV vaccine contains inactivated virus. The vaccine is more than 95% effective and is given in 2 doses: at 0 and at 6-18 months. A booster is recommended after 10 years. Travelers can be vaccinated starting at the age of 2 years. If the traveler will be in an endemic region prior to completing the series, then administration of HAV immunoglobulin is recommended.
Typhoid fever occurs in 1:3000 to 1:30,000 travelers per month. Risk is associated with travel to Asia, length of travel longer than 3 weeks, rural locations, and backpacking activities. The older vaccine, which is derived from an attenuated Salmonella typhi strain, is no longer recommended for use because it has only 50% to 80% effectiveness and is poorly tolerated. A newer oral vaccine uses the live attenuated S typhimurium strain Ty21a. This series is given in 4 doses, with a booster after 5 years. The vaccine is approved for travelers older than 6 years. An alternative typhoid vaccine is the parenteral Vi polysaccharide capsular subunit vaccine, which is convenient to administer and better tolerated than the older parenteral vaccine.
The risk of cholera is very low in travelers, occurring in approximately 2:1,000,000 travelers per month. The cholera vaccine is also poorly effective. Thus, the cholera vaccine is rarely recommended. In the United States, a parenteral, killed vaccine is available. The effectiveness ranges from 30% to 50% for 1-6 months. The series includes 2 doses, given 1-4 weeks apart, with a booster after 6 months. It has been approved for travelers older than 6 months. The vaccine is poorly tolerated.
Rabies is a serious concern for travelers. There is a 1% to 2% risk of rabies per animal bite per year in developing countries. Also, optimal postexposure prophylaxis is usually not available. Three vaccines are available for the traveler at high risk: human diploid cell vaccine (HDCV), the rabies vaccine absorbed (RVA), and the purified chick embryo cultured cell (PCEC) rabies vaccine. The vaccines are approved for all ages, and the series is given in 3 doses: 0, 7, and 21 or 28 days, with a booster after 6-36 months. Japanese encephalitis is a mosquito-borne viral infection occurring in Asia, associated with a 30% mortality rate. The disease is rare in travelers, affecting 1:1,000,000 travelers per month. Risk is associated with long rural exposure, especially in the peak transmission season. The vaccine is produced in mouse brain. The series includes 3 doses given at 0, 7, and 14 or 30 days, with a booster after 3 years. The vaccine is approved for travelers older than 1 year. Patients will require medical follow-up during vaccine administration because 0.6% develop a serious hypersensitivity reaction up to 10 days after vaccination.
In summary, travelers to underdeveloped countries should be up-to-date on their routine vaccines, will require HAV and yellow fever vaccines, and may require the meningococcal, typhoid, and/or rabies vaccines. The cholera and bacille Calmette-Guérin (BCG) vaccines are not recommended.
Malaria: A Surprise for the Return Trip
Malaria is the major life-threatening infection in travelers, stated Dr. Kevin Kain of Toronto Hospital, Ontario, Canada.[3] The worldwide incidence of malaria is on the rise, and there has been an increase in chloroquine-resistant malaria. There are approximately 70 million travelers at risk each year, with about 30,000 cases among travelers per year. The mortality rate is up to 15% to 30% with falciparum malaria. Most travelers develop malaria after they return home. Although chemoprophylaxis is not 100% effective, almost all cases are due to either failure to take prophylatic antibiotics or inadequate prophylaxis prescribed by the primary care provider. Prevention also involves avoiding mosquito bites with the use of DEET spray and permethrin-impregnated bed netting.
Drug Choices
The drug of choice for chemoprophylaxis is mefloquine (Lariam) because of its greater than 90% effectiveness against chloroquine-resistant falciparum malaria, which is highly prevalent. Mefloquine is more than 90% effective against chloroquine-resistant falciparum malaria. The only region mefloquine may not be effective is some border areas in Southeast Asia (Myanmar [Burma], Thailand, and Cambodia).
Contrary to popular perception, mefloquine is actually a well-tolerated medication. It has developed a reputation of having a high incidence of serious neurologic side effects, but the incidence of severe neurologic side effects is only 1:10,000, although 3% to 5% of patients may manifest some mild neuropsychiatric symptoms. Mefloquine is contraindicated in patients with a history of seizures or psychosis. It can be given to pregnant women and to infants traveling to high-risk areas who cannot postpone their trip. Mefloquine has the advantage of weekly dosing but has no "causal" therapeutic value in treating the liver stages seen with P vivax and P ovale. Thus, it must be taken for 4 weeks after returning from the trip.
One alternative is doxycycline, which is also more than 90% effective. However, it requires a daily dose of 100 mg, and it does not provide causal prophylaxis against the liver stage, thus requiring 4 weeks of post-travel administration. The drug is contraindicated in pregnant women and in children, and it may be associated with photosensitivity reactions or Candida overgrowth. Doxycycline is used primarily in Southeast Asia, where mefloquine has decreased effectiveness.
Chloroquine is effective prophylaxis in the few areas with chloroquine-sensitive malaria: the Caribbean basin, Central America, and parts of South America. Unfortunately, chloroquine-sensitive areas are quickly disappearing. One strategy to overcome chloroquine resistance is to combine this drug with proguanil. However, the combined therapy is only 50% to 70% effective against chloroquine-resistant malaria. Also, chloroquine is given weekly, and proguanil is given daily, which may be confusing to the traveler, resulting in increased risk of cardiotoxicity if the chloroquine is inadvertently taken daily.
Primaquine, originally used as a causal agent to treat malarial liver stages, can also be utilized as prophylaxis. Primaquine is 85% to 95% effective, but it must be given as a 30-mg daily dose. Also, travelers/patients need to be evaluated for G6PD deficiency. Since primaquine is a causal agent, it can be discontinued 5 days post-travel as opposed to the 4-week post-travel course required with mefloquine, chloroquine, and doxycycline. Tafenoquine is similar to primaquine, but is more effective, has fewer side effects, and is given weekly. G6PD deficiency will still need to be evaluated before use.
Malarone, a combination of atovaquone and proguanil, is another alternative for chemoprophylaxis. Like mefloquine, it has greater than 95% effectiveness, but malarone has a lower side-effect profile. It also has causal activity against liver stages of malaria. However, it needs to be given daily.
Azithromycin has the safest adverse-event profile in pregnant women and in children, but its effectiveness of 69% to 83% renders it unreliable as a prophylactic agent. Also, it must be taken daily, and it has no causal activity against the liver phases of malaria. In summary, mefloquine is the drug of choice for malaria prophylaxis due to its effectiveness against chloroquine-resistant falciparum malaria, its weekly administration, and its safety in pregnant women and in small children. (For further information, see "Prescription Drugs for Preventing Malaria," from the CDC [http://www.cdc.gov/ncidod/dpd/parasites/malaria/hcp_malaria_drugs.htm].)
It's Not All Piña Coladas and Umbrellas: Diarrheal Diseases in Travelers
Over 500 million international travelers are crossing national borders each year. At least 50 million of those are going from industrialized regions to Africa, Asia, Latin America, the Pacific Islands, or remote areas of Eastern Europe. At the top of the list are diarrheal illnesses.
According to Dr. Richard Guerrant of the University of Virginia School of Medicine, Charlottesville,[4,5] physicians should remember the "rule of 3's" pertaining to preventable illnesses in travelers: diarrhea (30%), malaria (3%), hepatitis A (0.3%), and typhoid (0.03%). The most common cause of travel-related diarrhea worldwide is enterotoxigenic Escherichia coli. However, there are some important regional differences. For example, fluoroquinolone-resistant Campylobacter jejuni diarrhea is an important issue in Southeast Asia, Vibrio parahaemolyticus accounts for a significant portion of infectious diarrhea in Japan, and Giardia and Cryptosporidium are common in Leningrad. Typical bacterial pathogens causing travel-related diarrhea require a large number of organisms to produce infections in a normal host. Fewer organisms may be required in individuals who are immunocompromised or on acid-suppression therapy. The exceptions to this are cysts of parasites, where as few as 1-10 organisms are required to produce infection, and of course Shigella infections. Cryptosporidium can be a particularly difficult pathogen to avoid. Most water filters have an inadequate pore size to eliminate this organism, and it tends to persist after chlorination. Boiling water is effective. Persistent diarrheal illnesses occur in 1% to 3% of travelers with diarrhea. Among the more common infectious etiologies are Clostridium difficile, cyclosporiasis, and cryptosporidiosis. Noninfectious diarrheal illnesses are often functional disorders or inflammatory bowel disease. Travelers' diarrhea in AIDS patients includes typical pathogens as well as Isospera, Microsporidium, Cryptosporidium, and mycobacteria. Travelers' diarrhea can be prevented with bismuth subsalicylate 2 tablets by mouth 4 times a day, according to Dr. Kain. However, the effectiveness of this agent is only 65%. Antibiotics such as fluoroquinolones or azithromycin are more than 90% effective. However, resistance to these drugs is increasing, such as in Campylobacter strains in Thailand. Treatment for mild cases of 1-2 bowel movements (BM) per day entails rehydration, electrolyte replacement, and loperamide (Imodium). Moderate cases (3-6 BM per day) include treatment with a fluoroquinolone for 1-3 days. Severe cases (> 6 BM per day) may require antibiotic treatment of longer duration. Resistance to trimethoprim/sulfamethoxazole is also becoming more widespread, noted Dr. Guerrant. He stressed the importance of hygiene as an effective preventive strategy for travel-related diarrheal illness. The "boil it, peel it, cook it, or forget it" philosophy is very effective.
Climb Every Mountain
Altitude sickness is classified into 3 syndromes: (1) acute mountain sickness (AMS), which is characterized by symptoms of headache, nausea, vomiting, and insomnia; (2) high-altitude pulmonary edema (HAPE), which includes dyspnea in addition to the symptoms of AMS; and (3) high-altitude cerebral edema (HACE), which is characterized by the same symptoms as AMS, with the addition of ataxia and mental status changes. The risk of altitude sickness is 30% at an altitude greater than 3000 m (9800 ft) and 75% at an altitude greater than 4500 m (14,800 ft). A prevention tactic is slow, gradual ascent of 500 m per day; acetazolamide (Diamox) 125-250 mg by mouth twice a day may be helpful. The primary mode of treatment is descent to lower altitudes.
Disease is Only Skin Deep: Tropical Dermatology
According to Dr. Jay Keystone of Toronto Hospital, Ontario, Canada,[6,7] tropical dermatology is not difficult to diagnose. However, accumulating vital information during history taking is essential. Specific points include travel region, duration of travel, and urban vs rural settings. Exposure history becomes particularly important. Swimming or exposure to animals or insects is helpful. Other questions to ask include: Did the dermatitis occur on exposed or unexposed skin? Was it linear or in clusters? What were the associated signs and symptoms? Dr. Keystone suggests categorizing these dermatologic diseases in groups -- maculopapular, nodular, linear, cellulitic, or ulcerative -- to help focus the differential diagnosis.
What follows is a list of diseases to consider when observing specific dermatologic findings:
Papular urticaria typically presents as a pruritic rash, often persisting for weeks to months. It is not indicative of persistent infestation, but rather is a characteristic allergic reaction. Jellyfish and related stings are best treated with vinegar or urea, not water or rubbing, which will worsen the situation.
A pustular papular rash is indicative of scabies. Ivermectin -- typically, 150 mcg/kg in a single dose -- may be a reasonable alternative to topical agents for treatment of scabies. Efficacy ranges from 70% to 100%. Ivermectin is not available in Canada, but it is in the United States.
An example of a nodular lesion is tungiasis, in which a female sandflea, Tunga penetrans, invades the skin of humans. This disorder may resemble myiasis, which can also cause a painful nodule, often boil-like. These infestations are dealt with quite differently. In tungiasis, the treatment is mainly surgical, whereas myiasis usually resolves with suffocation of the maggot larvae by covering the punctum with Vaseline, Krazy Glue, or bacon fat. Another way to remove the maggot in myiasis is with a snake venom extractor kit.
Caliber swelling is typical of loiasis; gnathostomiasis can produce a similar subcutaneous swelling, which is more likely in Africa, South America, or Southeast Asia. Linear lesions can be caused by cutaneous larvae migrans. The treatment is ivermectin or albendazole. A commonly seen phenomenon that is sometimes confused with cutaneous larvae migrans is phytophotodermatitis, a photosensitivity reaction to lime juice often linearly streaked by fingers on the skin. Portuguese-man-o'-war stings typically are linear lesions and are treated like other marine larval reactions.
Cellulitis secondary to bites is common and usually caused by streptococci. Some water-associated stings can result in cellulitis, such as stingray cellulitis, and must be treated with appropriate gram-negative rod coverage for Aeromonas, Vibrio, and Plesiomonas infections. Fluoroquinolones are a good choice for treatment.
Cutaneous leishmaniasis causes raised ulcers on the skin but can have a variety of appearances. Ulcers with a deep undermined edge in travelers to Africa or South America may be due to Mycobacterium ulcerans (Buruli's ulcer). Cutaneous amoebiasis can uncommonly cause perianal herpetic-appearing lesions. Ulcer in travelers from Southern Africa with a fever and a black eschar is commonly due to tick typhus, caused by Rickettsia species. Cutaneous anthrax is typically characterized by a black eschar with edema around the margins of the ulcer.
That All-important Travel History for the Returned Traveler
After a long trip, the returning traveler can present with fever, skin complaints, and eosinophilia, according to Dr. Mary Wilson of Mount Auburn Hospital, Cambridge, Massachusetts.[8,9] Fever has a large differential diagnosis in these patients, including several exotic and unfamiliar etiologies. The history is important in revealing factors such as incubation time (dengue and rickettsial diseases present within 2-20 days, typhoid within weeks, amoebic liver abscess within 6 months, and malaria from 1 week to several months), geographic location, season, urban or rural exposure, activities (such as exposure to animals, fresh water, salt water), underlying host conditions such as immune status, and prophylaxis (including vaccines and antimalarial medications). One must consider that the infection may have been acquired on return to the United States, or from other travel that was not mentioned. And one needs to consider noninfectious causes of fever, including deep vein thromboses and drug reactions.
The goals of the examination include identifying treatable causes of infection, controlling transmission, and avoiding serious sequelae. Lab tests should be directed by the differential diagnosis, including attention to noninfectious and non-travel-related infectious etiologies.
Eosinophilia in the Returned Traveler: It's Not Just Helminths
Although the most common cause of eosinophilia varies depending on the population under study, helminth infection is the biggest problem worldwide, according to Dr. Amy Klion of the National Institutes of Health.[10] Nevertheless, the initial evaluation of a traveler with eosinophilia should always consider noninfectious causes in order to avoid unnecessary workups.
Drug reactions are among the most common noninfectious causes. Interestingly, many of the drugs used for prophylaxis in travelers have been implicated, such as quinine and the fluoroquinolones, the latter of which typically cause an asymptomatic eosinophilia. Sulfa drugs can cause eosinophilia with associated pulmonary infiltrates, and tetracyclines may be associated with an eosinophilic hepatitis.
Disorders causing eosinophilia include allergy, asthma, drug hypersensitivity, parasitic infections, collagen vascular disease, neoplasia, and HIV. Less commonly, idiopathic hypereosinophilia and hyperadrenalism with eosinophilia may be seen.
Eosinophilia should be confirmed by calculating the absolute eosinophil count. Five percent to 10% of travelers and a higher percentage of immigrants to the United States are found to have eosinophilia in most series. Eosinophilia is variable, and it may be suppressed by some bacterial and viral infections or by corticosteroids. Diurnal variation in eosinophil counts leads to the highest levels in the early morning and the nadir in the evening.
Most nonparasitic infections result in eosinopenia, but there are notable exceptions, including resolving scarlet fever and fungal syndromes such as coccidioidomycosis and allergic bronchopulmonary aspergillosis. HIV is the most notable viral cause of eosinophilia, and it can have a variety of etiologies, including drug reactions, hypoadrenalism secondary to tubercular or cytomegaloviral infections of the adrenals, eosinophilic folliculitis, or HIV-associated immune dysregulation.
Protozoal infections typically do not cause eosinophilia. Exceptions may include Isospora belli or Sarcocystis infection. In general, finding a protozoal infection in a patient with eosinophilia should prompt a search for an alternative cause.
Ectoparasites causing eosinophilia include scabies and myiasis. With scabies, this reaction is secondary to sensitization to the mites and their eggs.
Eosinophilia can result from a variety of helminth infections. The degree of eosinophilia is one clue to the etiology. Intermittent eosinophilia is often seen with cysticercosis and echinococcal infections, related to leakage of the cysts. Marked eosinophilia, greater than 3000 cells/mL of blood, usually occurs early in infection, while the parasites are migrating through the tissues. For example, Ascaris causes profound eosinophilia while in the lungs. This occurs at a time when diagnosis may be difficult due to the fact that the patient may not yet be passing cysts in the stool.
Duration of eosinophilia also may assist in the diagnosis. Some organisms classically cause an eosinophilia that may last for years. Examples of long-term eosinophilia include eosinophilia associated with cysticercosis, echinococcosis (which may be intermittent), filariasis, and many fluke infestations. Hookworm infection typically causes a long-term, low-level eosinophilia. Strongyloidiasis can result in decades of elevated eosinophil counts.
Nevertheless, Dr. Klion concedes that a specific etiologic diagnosis is not made in up to 50% of patients with eosinophilia. However, empiric treatment remains controversial. GeoSentinel, An International Emerging Infectious Disease Network GeoSentinel, a global surveillance network for travel-related medicine, was created 5 years ago as a cooperative agreement between the International Society of Travel Medicine and the CDC's Division of Global Migration and Quarantine, according to Dr. David O. Freedman of the University of Alabama at Birmingham.[11,12] (The GeoSentinel Web site is under construction at the ISTM site [http://www.istm.org/].) This program has created a worldwide communications and data network of tropical and travel medicine clinics around the world for tracking infectious diseases as they circle the globe with our internationally mobile population. The goals of the GeoSentinel are to monitor global trends in travel-related morbidity while identifying risk factors for these travelers and to help in response to urgent health queries by the public at large. In addition, the network aims to develop educational programs and to enable travel medicine providers to have rapid responses to critical situations during the data collection period.
The surveillance instrument is a 1-page data form filled out by both patient and physician. Information obtained includes travel history, purpose of trip, chief complaint, and final diagnosis. The form is straightforward and brief so as to improve reporting, since most participating clinicians do so on a voluntary basis. Some clinics are using an electronic data collection system.
The essence of the network is 26 core surveillance sites, with the capability of responding to queries from some 1800 ISTM members in 55 countries around the world, emphasizing the concept of a network of networks. As of June 2000, the network has accumulated data on over 11,000 patients to and from over 13,000 destinations, spanning essentially every country in the world. Many patients have multicountry itineraries and present with more than 1 diagnosis.
Based on a recent analysis of data, diarrhea was the most frequent diagnosis for the nonimmigrant traveler. Dermatologic pathology accounted for up to 25% of complaints at many travel clinics, making expertise in this area a prerequisite for care providers. Other frequent diseases encountered in returning travelers included malaria and various acute respiratory tract infections. About 10% of patients who presented with a travel-related complaint remain without a diagnosis. Interestingly, neuropsychiatric disease accounted for a significant portion of complaints. It is currently unclear whether some of these patients may be suffering from yet undiagnosed infectious syndromes.
Similar analyses for immigrants are available, with diarrhea, positive tuberculin skin tests, and dental caries being the most common issues. On screening exams, Blastocystis hominis is commonly identified in the stools of immigrants. However, it is unclear whether this organism actually causes disease in this population or is merely a commensal.
Additional analyses looked at relative risk according to purpose of travel. Although frequently thought of as lower risk, business travelers had 2 times the relative risk of contracting a travel-related disease than general tourist travelers. Recent immigrants who returned to their native country to visit friends and relatives were shown to be at up to 8 times the risk, since they typically do not seek pretravel care.
A recent report highlighted GeoSentinel's response capabilities. The network identified a cluster of dengue fever in travelers returning from Bangladesh. Combined with case finding from the CDC, this resulted in communication to travel clinics globally and was rapidly posted on the CDC Web page. Clearly, this surveillance system is useful to those practicing travel medicine.
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