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PubMed1991

Air travel in patients with chronic obstructive pulmonary disease.

Air travel exposes patients with chronic obstructive pulmonary disease to the risk of severe hypoxemia. We sought to determine the frequency and outcome of airline travel in patients with chronic obstructive pulmonary disease. A cohort of 100 patients (76 men and 24 women; age 67 +/- 7 years [mean +/- SD]) with severe chronic pulmonary obstructive disease examined by means of spirometry (forced expiratory volume in the first second, 0.04 +/- 0.35 L), all military retirees, or their dependents, comprised the study population. Forty-four patients traveled by commercial air carrier over a 28-month interval, giving an annual frequency of 18.9% of these patients per year. The group that did not travel by air (n = 56) had a lower mean value for forced expiratory volume in the first second and greater prevalence of home oxygen use than did the group that did travel by air. Twelve of the travelers (27.3%) consulted a physician beforehand. Flights reached foreign destinations for 22.7% of patients. The median duration of the longest flight segment was 3 hours. A minority of patients (34.3%) occupied seats in the smoking sections of aircraft. A majority (56.8%) ambulated aboard the aircraft during flights. Eight patients (18.2%) reported transient symptoms during air travel. We conclude that patients with chronic obstructive pulmonary disease travel with appreciable frequency, often without medical consultation, and develop symptoms in some cases.

Aerospace Medicine↗
PubMed1991

Evaluation of the traveler. An introduction to emporiatrics for the emergency physician.

Travel medicine, or emporiatrics, presents an additional challenge to the practicing emergency physician. In this time of increased travel for business and pleasure, travel history should become a routine part of patient evaluation. While the emergency physician may not need to become facile with specific details concerning immunizations and prophylaxis, he or she should have a good working knowledge of these in order to provide the potential traveler with some basic information and to be able to adequately evaluate the returned traveler who becomes ill and seeks care. Air travel allows many travelers to arrive back in the United States before manifesting symptoms and signs of illness acquired abroad. Many of these illnesses are not usually found in the United States. Late diagnosis of certain illnesses, such as falciparum malaria, may increase the morbidity and mortality. As such, travel history should become a routine part of patient evaluation, and the physician should have a good working knowledge of illnesses that may be acquired abroad.

Diarrhea↗
PubMed1985

[Typhus epidemiology in Switzerland 1980-1983. Slight or lack of effectiveness of the live vaccine Vivotif in tropical travel].

214 cases of typhoid fever (TF) occurring in Switzerland between January 1980 and December 1984 were analyzed for travel history, vaccine status and nationality. A subgroup of Swiss tourists who acquired TF in India was compared to a sample of healthy Swiss tourists who travelled to India in 1983 to determine the factors predisposing to TF. Eighty cases of TF occurred in Swiss tourists to the Third World, of whom 26 had travelled in India. Among the latter, the length of stay was longer than in the control sample of 258 healthy tourists, and "trekking" (travelling off the usual tourist routes with backpacking) was more frequent. 20 of the 80 patients had been vaccinated with the live oral typhoid vaccine Vivotif (strain S. typhi Ty 21a, contained in gelatine capsules, to be taken with bicarbonate capsules), marketed in Switzerland in 1981-1984. Comparison of the vaccination rates in case and control groups indicated that the vaccine efficacy was not significantly different from 0% during the time of observation. This lack of efficacy may be related to inadequate dosage and to the lack of stability of the vaccine. Forty cases of TF occurred in Swiss who had travelled in European countries, of whom 8 had not travelled outside Switzerland. The remaining 94 cases occurred in non-Swiss travellers, a majority of whom were from Mediterranean countries. TF in Switzerland was associated with a history of travel in 96% of cases. The live oral typhoid vaccine Vivotif was ineffective between 1981 and 1983.(ABSTRACT TRUNCATED AT 250 WORDS)

Carrier State↗
PubMed1994

Epidemiology and prevention of hepatitis A in travelers.

OBJECTIVE: To assess the risk of hepatitis A in international travelers and to recommend preventive measures. DATA SOURCES: Index Medicus, 1974 through 1983; MEDLINE, 1984 through 1993; and unpublished data of the Centers for Disease Control and Prevention. STUDY SELECTION: Review of all retrospective and cohort studies on hepatitis A and other vaccine-preventable diseases in travelers, of seroepidemiologic surveys of hepatitis A virus (HAV) antibodies in travelers, of data on the various hepatitis A vaccines, of economic analyses, and of recommendations of recognized organizations. DATA EXTRACTION: Independent analysis by multiple observers. DATA SYNTHESIS: The incidence rate for unprotected travelers, including those staying in luxury hotels, is estimated to be three per 1000 travelers per month of stay in a developing country. Persons eating and drinking under poor hygienic conditions have a rate of 20/1000 per month. This makes hepatitis A the most frequent infection in travelers that may be prevented by immunization. In many industrialized countries persons born after 1945 have an HAV antibody seroprevalence (immunity) of less than 20%. New inactivated HAV vaccines induce protective antibodies in more than 95% of recipients and offer protection estimated to last for 10 years or more, whereas protection by immune globulin lasts only 3 to 5 months. CONCLUSIONS: Hepatitis A vaccine, or immune globulin where HAV vaccine is not available, is recommended for all nonimmune travelers visiting developing countries. Prescreening for antibodies to HAV in travelers living in countries with low prevalence is usually not necessary in persons born after 1945.

Cost-Benefit Analysis↗
PubMed1995

Stand-by treatment of suspected malaria in travellers.

Travellers to malarious areas are increasingly advised to carry an emergency medication for self-treatment of suspected malaria in absence of medical attention. However, no data are available so far how travellers cope with self-diagnosis and stand by treatment (SBT). We therefore investigated the frequency, circumstances and outcome of emergency self-treatment for suspected malaria in German travellers. 3434 travellers were recruited for an open prospective study by 28 different travel clinics in Germany. 2867 travellers (90.1%) who returned questionnaires after their journey were analyzed. 40 travellers (1.4%) reported about SBT during their journey. Significant Plasmodium falciparum antibody levels could be demonstrated in only 4 of 37 SBT users (10.4%). In another 127 travellers with febrile episodes but without SBT use, no malaria was indicated by follow-up and/or serology.

Adult↗
PubMed1997

Guidelines for the prevention of malaria in travellers from the United Kingdom. PHLS Malaria Reference Laboratory, London School of Hygiene and Tropical Medicine.

These guidelines on malaria prevention are an aid to health care workers who advise travellers, particularly those who will be overseas for less than a year. They represent a virtual consensus of the views of 44 doctors, nurses, and pharmacists with special expertise in malariology or travel medicine who met to develop them in 1996 (see list on R152). The guidelines are in three parts. The first part is a summary that emphasises modifications to the advice given in the last set of guidelines, published in 1995. The second part discusses the issues addressed in formulating the guidelines. Doctors, practice nurses, and pharmacists are asked to read this section to avoid doing harm by giving chemoprophylaxis without due attention to the traveller's history or destination and by using oversimplified lists of recommendations by country. The second part also addresses the health care worker's consultation with prospective travellers. The third part gives specific recommendations for travellers to specific destinations and some details of individual drugs. Fuller information on some points was given in earlier versions of the guidelines, which should not be discarded. Meetings of the sort described above have been held since 1980 and the group's membership has included people with varied views and experience. The views expressed in these guidelines reflect experienced professional opinion, since data are inadequate for unequivocal views to be given on several issues. There is often a range of acceptable options, but to meet the requests of general practitioners the guidelines try to give one recommended option and state alternatives, suggesting when and how different regimens can be used to good effect. Decisions on the terms under which different drugs are licensed for use are the responsibility of the Licensing Authority, advised by the Committee on Safety of Medicines (not of these guidelines). The guidelines should be read as a supplement to and not as a substitute for the relevant data sheets. Chemoprophylaxis lies somewhere between vaccination (for which people expect governments to lay down schedules) and treatment of ill people (for which each physician does what seems most appropriate) in concept and practice. The risks of malaria need to be balanced against the risks of the preventive measures, on the basis of the data available. Travellers may ask for an explanation of these risks and doctors and practice nurses need to be well informed and able to present their knowledge to travellers. The second part of these guidelines may be of use to prospective travellers who wish to read about the options themselves. All readers are recommended to read part two in its entirety to get a balanced picture.

Disease Transmission, Infectious↗
PubMed1998

Immunizations for international travelers.

Each year more than 45 million Americans travel abroad for work or pleasure, and over 20 million of these travel to rural areas or developing countries. While the major medical risks of international travel are often exaggerated, the incidence of minor illness is not. Persons going to Asia, Africa, or Latin America for one month run a 65% to 75% chance of becoming ill, although only 1% will require hospitalization. The two most common illnesses that affect travelers, which do have immunizations and are often overlooked by physicians, are influenza and hepatitis A. The risk of illness to the traveler varies by health and age status, by the region to be visited, by the time of year, and by the length of the journey. Immunization advice for the traveler, therefore, is complicated and is best approached in a systematic manner. This article outlines six steps to sound immunization advice. These steps include ascertaining the traveler's special individual needs, routine immunization status, and routine travel immunization status, as well as the entry requirements for the country to be visited, geographically indicated vaccines, and immunizations as indicated for extended stays abroad.

Adult↗
PubMed1998

[Outbreak of schistosomiasis in a group a travellers returning from Burkina Faso].

BACKGROUND: Schistosomiasis in Spain is always an imported disease mainly presented in travellers from endemic areas with a history of having bathed in fresh water and in immigrants from these areas. A group of travellers presenting infection by schistosomes following an 8-day journey to Burkina Faso. PATIENTS AND METHODS: The travellers, residents of Gran Canaria (Spain), who had bathed in fresh water were studied by schistosomiasis serology and parasitologic examination in stools and urine. RESULTS: A total of 29 travellers were studied, 20 (69%) of whom were considered to be infected, on presenting positive serology and/or coproparasitologic examination. Fourteen of the infected patients presented clinical symptomatology compatible with the Katayama syndrome, while 6 were asymptomatic. The mean time to appearance of the symptoms was 27 days and these were most frequently fever, headache, neck pain, diarrhea and arthromyalgia together with eosinophilia achieving a mean value of 3,513 eosinophils/microliter. All the infected travellers presented positive serology and in 5 eggs of a Schistosoma mansoni were observed in stools. All the infected patients were treated with praziquantel. CONCLUSIONS: Limited exposure by bathing in fresh water in this group of travellers led to a high rate of infection. The diagnosis of schistosomiasis should be considered in any traveller from an endemic area with a history of having bathed in fresh water. In the case of an outbreak, investigation of all the travellers who had bathed is recommendable given that the infection may be asymptomatic.

Adult↗
PubMed1999

Travel distance and mass gain in wintering blackbirds.

Birds that range over a large area will have a greater mass-dependent risk of predation than more sedentary birds. Birds that travel more may then reduce winter mass gain to compensate for the increased predation risk that greater travelling entails. I tested whether European blackbirds, Turdus merula, that travelled more in winter had a lower mass than more sedentary birds, independently of any confounding effects of food supply on both ranging behaviour and mass gain. I measured change in winter mass and amount of food eaten in conjunction with the distance that blackbirds travelled to a randomly sited mobile feeder. Blackbirds that travelled shorter distances (per trip and in total) and less often to the feeder had the highest mass midwinter relative to their spring mass. Blackbirds with a higher mean mass midwinter also travelled, on average, shorter distances to the feeder. The distance an individual blackbird travelled to the feeder at any one time was probably independent of the state of its daily energy reserves (how much of its daily total mass gain it had achieved at that point). The relationship between distance travelled and mass was probably independent of food supply because distances actually increased at the end of the winter and the amount of food eaten per individual changed little. More mobile blackbirds were therefore likely to have compensated for any increases in predation risk associated with their greater ranges by decreasing winter mass gain, but will have had an increased risk of starvation because of their lower mass. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2007

Travel distance estimation from visual motion by leaky path integration.

Visual motion can be a cue to travel distance when the motion signals are integrated. Distance estimates from visually simulated self-motion are imprecise, however. Previous work in our labs has given conflicting results on the imprecision: experiments by Frenz and Lappe had suggested a general underestimation of travel distance, while results from Redlick, Jenkin and Harris had shown an overestimation of travel distance. Here we describe a collaborative study that resolves the conflict by tracing it to differences in the tasks given to the subjects. With an identical set of subjects and identical visual motion simulation we show that underestimation of travel distance occurs when the task involves a judgment of distance from the starting position, and that overestimation of travel distance occurs when the task requires a judgment of the remaining distance to a particular target position. We present a leaky integrator model that explains both effects with a single mechanism. In this leaky integrator model we introduce the idea that, depending on the task, either the distance from start, or the distance to target is used as a state variable. The state variable is updated during the movement by integration over the space covered by the movement, rather than over time. In this model, travel distance mis-estimation occurs because the integration leaks and because the transformation of visual motion to travel distance involves a gain factor. Mis-estimates in both tasks can be explained with the same leak rate and gain in both conditions. Our results thus suggest that observers do not simply integrate traveled distance and then relate it to the task. Instead, the internally represented variable is either distance from the origin or distance to the goal, whichever is relevant.

Adult↗
PubMed2002

Sensitivity of ray travel times.

Ray in a waveguide can be considered as a trajectory of the corresponding Hamiltonian system, which appears to be chaotic in a nonuniform environment. From the experimental and practical viewpoints, the ray travel time is an important characteristic that, in some way, involves an information about the waveguide condition. It is shown that the ray travel time as a function of the initial momentum and propagation range in the unperturbed waveguide displays a scaling law. Some properties of the ray travel time predicted by this law still persist in periodically nonuniform waveguides with chaotic ray trajectories. As examples we consider few models with special attention to the underwater acoustic waveguide. It is demonstrated for a deep ocean propagation model that even under conditions of ray chaos the ray travel time is determined, to a considerable extent, by the coordinates of the ray endpoints and the number of turning points, i.e., by a topology of the ray path. We show how the closeness of travel times for rays with equal numbers of turning points reveals itself in ray travel time dependencies on the starting momentum and on the depth of the observation point. It has been shown that the same effect is associated with the appearance of the gap between travel times of chaotic and regular rays. The manifestation of the stickiness (the presence of such parts in a chaotic trajectory where the latter exhibits an almost regular behavior) in ray travel times is discussed. (c) 2002 American Institute of Physics.

Journal Article↗
PubMed1998

Age and the human cochlear traveling wave delay.

OBJECTIVE: Cochlear physiologic changes that occur with aging also may affect the mechanics and filtering properties of the cochlea. In studying aging effects, it is also necessary to consider the effects of hearing threshold losses because thresholds generally increase with age, and threshold losses also affect the filtering properties of the cochlea. A distortion product emission (DPE)-based measurement of human cochlear traveling wave delays allows an indirect assessment of the mechanics of the traveling wave and how it might change with age. DESIGN: The cochlear traveling wave delay has been derived from DPE phase measurements using an f1 sweep paradigm (Kimberley, Brown, & Eggermont, 1993). In the present study, traveling wave delay was estimated from DPE phase measurements taken from the left ears of 91 subjects (22 to 78 yr) with auditory thresholds ranging from normal hearing (< or = 25 dB SPL, ANSI 1969) to mild cochlear hearing damage. No one under the age of 65 had hearing losses exceeding 40 dB SPL to 8 kHz. Pure-tone thresholds were determined at eight frequencies through a 4-interval, forced-choice, adaptive-level psychophysical test. DPE phase and amplitude measurements were made at these eight frequencies using CUBeDIS-related software (AT&T Bell Labs). Round-trip traveling wave estimates were calculated from the DPE phase measurements for each of the eight f2 frequencies (places). RESULTS: Traveling wave delays estimated using DPE phase were not significantly affected by mild hearing losses. Traveling wave delay, however, does increase slightly with age. Optimal f2/f1 ratio and associated DPE amplitude also were tested for age or threshold effects. The optimal f2/f1 ratio remained unaffected by age or hearing loss but decreased with increasing frequency. The maximum DPE amplitude decreased with both advancing age and increasing pure-tone threshold, so it was impossible to isolate the contribution of each individual factor. CONCLUSIONS: Mild hearing losses do not affect the round-trip traveling wave delay. There is a slight age dependence, however. This may suggest that there are age-related but threshold-independent factors that may alter such properties as basilar membrane stiffness or cochlear fluid composition. The relationship between maximum DPE amplitude and threshold, at the frequencies tested, is a better predictor of hearing thresholds than the DPE amplitude as obtained from a fixed ratio DPE amplitude measurement.

Adult↗
PubMed1996

A Survey of Travel Clinics Throughout the World.

Background: The growth of travel medicine as a specialty has been marked by a dramatic increase in the number of travel clinics worldwide. A survey was conducted of travel clinics to assess the current practice of travel medicine. Methods: A questionnaire was sent to members of the International Society of Travel Medicine, asking questions about clinic demographics, categories of advice given and immunizations available, and educational training of clinic personnel. Results: Responses from 341 clinics were analyzed; 57% were located in the United States; 21% in Europe; 6% in the United Kingdom or Ireland; 6% in Canada; and 11% from other areas of the world. Most clinics were private (41%); however, many other affiliations were represented, including schools of medicine (20%), hospitals (10%), and occupational medicine and student health practices (10%). The median number of patients seen per year was 750; however, the range was 6 to 50,000. Each clinic offered many vaccines, and advice for the prevention of malaria, diarrhea, and insect avoidance was given over 95% of the time. Providers of advice were nurses (57% of the time) and physicians (83%); however, in the United States nurses gave advice independently more frequently (22% vs. 8%, p <.001) than in other parts of the world. Clinics also frequently gave telephone advice (15% charged for this service) and evaluated ill returned travelers. Over 60% of physicians had trained in infectious diseases and/or tropical medicine, although there were training differences between regions of the world. Conclusions: Travel clinics throughout the world demonstrate similarities as well as differences in practice. Defining these will help in determining practice needs in the growing field of travel medicine.

Journal Article↗
PubMed1996

Risk Factors for Typhoid Fever in Travelers.

Background: The incidence of typhoid fever in the developing world remains high and has been estimated at 540 cases per 100,000 of the population per year. International travelers to such areas are at risk of infection, especially if they travel under low hygienic standards. Methods: In order to identify the risk factors leading to infection in travelers and expatriates, travel histories, anamnestic and clinical features of 31 patients with typhoid fever, who presented to a German travel clinic, were investigated. Results: Compared to the total patient population of the outpatient clinic during the period of investigation (n = 17,029 patients), patients who presented with typhoid fever were older (39 years versus 31 years, p <.001) and traveled longer (58 days versus 19 days, p <.001). While only 19.2% of the total patient population had traveled to the Indian subcontinent prior to referral, 35.4% of the patients with typhoid fever had acquired the infection there (p <.001). Similar results were obtained for South East Asia and Indonesia: twenty percent of the total patient population traveled there in contrast with 32.2% of patients with typhoid fever (p <.001). Latin America was visited by 16.3% of all patients, but only 6.4% of patients with typhoid (p <.001).

Journal Article↗
PubMed1996

Prevention and Management of Cardiovascular Events during Travel.

Traveling has been associated with an increased incidence of cardiovascular events among adult travelers who have existing cardiopulmonary diseases.1-6 Assessment of the patient's cardiovascular status and risk prior to travel represents the first step in the evaluation process and was discussed thoroughly in a paper by the same authors published in the previous issue of Journal of Travel Medicine. Therefore, prevention and management of cardiovascular events during travel are very important for the physicians who are involved in treating patients with heart disease who intend to travel. The current data regarding this crucial issue are limited. After careful assessment, the physician specializing in travel medicine needs to provide patients with existing cardiopulmonary disease with specific instructions to prevent adverse cardiovascular events during travel, as well as measures that they should undertake if such an event occurs.

Journal Article↗
PubMed1997

Impact of Travel-Related Health Impairments.

Background: Few recent data exist on the impact of travel-related health problems. Methods: A cohort study was conducted with follow-up by questionnaire of 2567 persons who had consulted the Zurich University Travel Clinic for travel health advice prior to visiting a developing country or eastern Europe. Of those questioned, 2109 (82.2%) could be evaluated. Results: More than one-third (800; 37.9%) had a health impairment, mainly illness leading to medical consultations in 224 (10.6%) individuals. Incapacitation was reported by 303 (14.4%) travelers, accounting for 2% of the total time abroad. The most frequent reasons for incapacitation were diarrhea and the common cold, particularly when accompanied by fever. Some 57 (7.1%) travelers consulted a doctor while abroad, and more than twice as many did so after returning home. Conclusions: This survey illustrates that despite efforts of travel medicine, the attack rate of health impairments remains virtually unchanged compared to 20 years ago. It provides one of the first overviews of incapacitation in travelers. To reduce the duration of incapacitation, one may wish to consider a travel kit which allows the patient self therapy for frequent and uncomplicated ailments.

Journal Article↗
PubMed1981

Traveler's diarrhea associated with rotavirus infection: analysis of virus-specific immunoglobulin classes.

An enzyme-linked immunosorbent assay for the detection of rotavirus-specific immunoglobulin G (IgG), IgM, and IgA antibodies was used in a serological study of Traveler's diarrhea. The antigenically related simian rotavirus (SA-11) was used as antigen in this study. Serum was obtained from two groups of volunteers before travel (pre-travel) and at various times after arrival at their destination (post-travel). One group consisted of 47 American Peace Corps volunteers who traveled to Honduras, and the second group consisted of 66 Panamanian travelers who visited Mexico. An association between rotavirus and Traveler's diarrhea was found in each group with 36% of American Peace Corps volunteers and 30% of Panamanians with diarrhea demonstrating a greater than or equal to 4-fold increase in rotavirus antibody titers in the post- as compared to the pre-travel specimens. While no rotavirus-specific IgM antibody was detected in any serum tested, increases in specific antibody were found in both the IgG and IgA immunoglobulin classes.

Adult↗
PubMed2000

The framing of drivers' route choices when travel time information is provided under varying degrees of cognitive load.

In two experiments, participants chose between staying on a main route with a certain travel time and diverting to an alternative route that could take a range of travel times. In the first experiment, travel time information was displayed on a sheet of paper to participants seated at a desk. In the second experiment, the same information was displayed in a virtual environment through which participants drove. Overall, participants were risk-averse when the average travel time along the alternative route was shorter than the certain travel time of the main route but risk-seeking when the average travel time of the alternative route was longer than the certain travel time along the main route. In the second experiment, in which cognitive load was higher, participants simplified their decision-making strategies. A simple probabilistic model describes the risk-taking behavior and the load effects. Actual or potential applications of this research include the development of efficient travel time information systems for drivers.

Adult↗