Summer Travel: News Clinicians (and Their Patients) Can Use

By Philip R. Fischer, MD, DTM&H

Professor of Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN

The pandemic has waned. Summer vacation has arrived. Airports are crowded. Planes are full. New science can guide us as we and our patients travel this season. Now, Infectious Disease Alert briefly reviews 13 new and in-press papers from the two main travel medicine journals.

What to Pack

SOURCE: Benz U, Traore MM, Revay EE, et al. Effect of textile colour on vector mosquito host selection: A simulated field study in Mali, West Africa. J Travel Med 2024;31:taae049.

Investigators in Mali lured mosquitoes to traps that released material that simulated human breath. The traps were covered with black, white, or black-and-white striped cloths. A total of 21,940 mosquitoes were trapped — 70% Culex, 18% Aedes, and 12% Anopheles. Aedes mosquitoes were most trapped by (and, thus, attracted to) striped cloth-covered traps, Culex to either black or striped cloths, and Anopheles to black cloths. Thus, travelers wanting to avoid both day-biting and night-biting mosquitoes should pack (and wear) light-colored or white clothing (in addition to using other mosquito bite avoidance strategies).

Something to Swallow

SOURCE: Alharbi BF, Alateek AA. Investigating the influence of probiotics in preventing traveler’s diarrhea: Meta-analysis based systematic review. Travel Med Infect Dis 2024;59:102703.

Pre-travel education about hand hygiene and selection of foods and beverages during travel is incompletely protective against developing diarrhea during travel, and tens of millions of international travelers suffer from travelers’ diarrhea each year. Scientists in Saudi Arabia performed a meta-analysis and systematic review of 10 randomized controlled trials using probiotics for the prevention of travelers’ diarrhea. Some lactobacilli (but not L. acidophilus), Saccharomyces cerevisiae, and Saccharomyces boulardii seemed to possibly have a mildly protective effect (of borderline statistical significance), but study traveler and destination variations made it difficult to generalize results. Is it worth packing and using a probiotic to prevent travelers’ diarrhea? Maybe a little bit.

What to Plan Not to Do

SOURCE: Plaza PI, Gamarra-Toledo V, Rodríguez Euguí J, et al. Pacific and Atlantic sea lion mortality caused by highly pathogenic Avian Influenza A(H5N1) in South America. Travel Med Infect Dis 2024;59:102712.

Those wanting to travel to either the Atlantic or Pacific coasts of South America to see sea lions might want to reconsider. During the first 10 months of 2023, more than 24,000 sea lions died from pneumonia and encephalitis due to highly pathogenic avian influenza A (H5N1) along the coasts of Peru, Chile, Argentina, Uruguay, and Brazil. (Otter, dolphins, and porpoises also were affected.) During 2023, the fatal outbreak seemed to spread southward along the Pacific Coast of South America and then northward up the Atlantic Coast. It is presumed that the sea lions were infected by eating infected birds, but spread between sea lions has not been ruled out. Whether humans in close proximity to infected marine mammals can become ill remains to be seen.

Substance Use and International Travel

SOURCE: Charoensakulchai S, Onwan M, Kanchanasurakit S, et al. Recreational substance use among international travellers. J Travel Med 2024;31:taae012.

A group from Thailand and Malaysia reviewed 58 articles about recreational substance abuse in international travelers. Prevalence rates varied between studies, but up to one-third used cannabis, up to one-third became intoxicated with alcohol, and a similar number used ecstasy (3,4-methylenedioxymethamphetamine or MDMA). (These rates are more than twice as high as among non-travelers.) Fewer travelers used cocaine, psychedelics, and methamphetamine. The consequences of substance use during travel included neuropsychiatric disorders, accidents and injuries, risky sexual behaviors, and blood-borne infections. In fact, 22% had neuropsychiatric symptoms related to drug use — panic, anxiety, depression, and/or psychosis. Males were more likely than females to abuse substances, and the highest rate of activity was found in those aged 16-35 years. Several of the studies showed that those who used substances at home tended to increase their use of substances when traveling, sometimes with adverse health and legal consequences.

Travel and Sexually Transmitted Infections

SOURCES: Caumes E. Travel and sex: Addressing the spread of sexually transmitted infections. J Travel Med 2024;31:taae066.

Shiferaw W, Martin BM, Dean JA, et al. A systematic review and meta-analysis of sexually transmitted infections and blood-borne viruses in travellers. J Travel Med 2024;31:taae038.

Santaolaya C, Malhotra J, Fowler JA, et al. Integrating sexual and reproductive health into pre-travel consultations. J Travel Med 2024;31:taae024.

The link between international travel and sexually transmitted infections has been obvious for centuries. The spread of syphilis with sailors returning to Europe with Columbus, the spread of human immunodeficiency virus (HIV) from Africa to the world in the last century, and the recent spread of mpox beyond its usual “homes” in Africa to the rest of the world during the 2020s highlight the risks of unsafe sex during travel. New infections with Gonococcus and Chlamydia, as well as other pathogens, are seen in travelers returning to Europe. Those at most risk of sexually transmitted infections during international travel are young adult males who do not seek pre-travel consultation, especially males who have sex with males. Since travel is such a frequent opportunity, preventive educational discussions about avoiding unsafe sexual contact should be held during pre-travel consultations and can be appropriate when seeing such patients even outside of pre-travel consultations.

What Not to Bring Home

SOURCES: Norman FF, Chen LH. Imported Buruli ulcer — is there risk for travellers? J Travel Med 2024;Apr 9:taae057. doi: 10.1093/jtm/taae057.

Bohelay G, Guyot A, Billard-Pomares T, et al. Extensive buruli ulcer in a patient returning from Mali and Senegal. Travel Med Infect Dis 2024;60:102725.

Remember Buruli ulcer, the skin nodules that ulcerate with destructive ulcers undermining the skin? The cause is Mycobacterium ulcerans, but the mode of transmission is unknown. Sixteen cases in travelers were reviewed by Norman and Chen, including patients of both sexes and of both pediatric and adult ages. Many but not all cases arise in Africa. The diagnosis often is delayed. Ulcers may be extensive, as illustrated by Bohelay and colleagues. Fortunately, effective treatment is possible, although debridement and skin grafting sometimes are necessary.

We Had a Gas

SOURCE: Weitzel T, Brown A, Libman M, et al. Intestinal protozoa in returning travellers: A GeoSentinel analysis from 2007 to 2019. J Travel Med 2024;31:taae010.

Approximately 40% of travelers from high-income countries visiting low-resourced countries develop gastrointestinal symptoms, usually self-limited diarrhea. However, sometimes diarrhea persists and is due to intestinal protozoa. A network of travel and tropical medicine clinics reported on 2,517 cases of intestinal protozoal disease in international travelers. Giardiasis was most common (83% of the cases), but cryptosporidiosis, cyclosporiasis, and rare cystoisosporiasis also were seen. Giardiasis and cryptosporidiosis were identified most frequently after travel in south-central Asia and sub-Saharan Africa. Cyclosporiasis was associated with travel in southeast Asia and Central America. The diagnosis of protozoal disease often is delayed, and clinicians should readily consider protozoal infections when post-travel diarrhea persists, especially with bloating and increased gas production.

Oh, My Aching Joints

SOURCE: de la Calle-Prieto F, Barriga JJ, Arsuaga M, et al. Clinical profile and management of a Spanish single-center retrospective cohort of patients with post-chikungunya associated complications. Travel Med Infect Dis 2024;60:102726.

A team from a single center in Spain reviewed 119 patients with chronic complications of chikungunya virus infection. Two-thirds were male, with median age 40 years (with teens through elderly individuals included), and 87% following travel in Central or South America. Acutely, most patients had fever, adenopathy, and arthralgia of multiple joints (most commonly wrists, knees, and ankles). Those same joints were most involved chronically, and more joints were involved concurrently with the chronic phase than with the acute infectious phase of the illness. The chronic arthralgia sometimes resolved but then recurred; 61% of patients needed to alter their daily activities because of the joint pain. Acetaminophen and non-steroidal anti-inflammatory agents were commonly used. Methotrexate and steroids were rarely used. Mosquito bite avoidance measures could presumably have prevented the acute infection and the chronic pain.

Imported Gestational Malaria

SOURCE: Imbert P, Nizard J, Werkoff G, et al. Pregnancy outcomes in women with imported malaria in mainland France: A retrospective study from 2004 to 2014. Travel Med Infect Dis 2024;60:102727.

Researchers in mainland France retrospectively reviewed outcomes of 55 women treated for imported gestational malaria (95% due to Plasmodium falciparum) during a 10-year period. Twenty percent were primigravidae. Sixteen percent of the pregnancies ended with miscarriage, and one with stillbirth. Most surviving babies were born healthy at term, but 17% were born pre-term, and 21% were of low birthweight. Placental, but not congenital, malaria was identified. Overall, the authors identified significant complications in 48% of offspring despite good treatment of maternal malaria; they suggest enhanced efforts to prevent malaria during pregnancy.

Procalcitonin Level and Malaria Prediction

SOURCE: Tielli A, Ouorou R, Pull L, et al. Might procalcitonin help predict imported falciparum malaria in children? Travel Med Infect Dis 2024;60:102731.

What about when a child presents to an emergency department with fever after travel in a malaria-endemic area? Besides clinical exam (with attention to hematologic and neurologic statuses) and parasitological testing (for percent of red cells harboring parasites), can any other test distinguish non-malaria from uncomplicated malaria and from severe malaria? A retrospective case-control study of febrile returned travelers in France determined that if the procalcitonin level is less than 0.65 ng/mL, there was less than a 2% chance that the child had malaria. If the procalcitonin level was greater than 6.17 ng/mL, it was likely that the child had complicated/severe malaria.