A man in his early 30s presented with fever, widespread pruritic rash and deranged liver function tests shortly after returning from a religious pilgrimage. Initial assessment focused on infectious and travel-related causes given recent international travel. Investigations revealed marked eosinophilia, lymphocytosis and a mixed hepatocellular-cholestatic liver injury. Extensive viral, parasitic and autoimmune testing was negative. Despite partial symptomatic improvement following cessation of recently initiated allopurinol, the patient developed progressive eosinophilia and new lymphadenopathy. Multidisciplinary review supported a diagnosis of drug reaction with eosinophilia and systemic symptoms (DRESS), with allopurinol identified as the most likely culprit. Oral corticosteroid therapy led to rapid clinical and biochemical improvement, with normalisation of eosinophil count and liver function prior to discharge. This case highlights the diagnostic challenge of drug hypersensitivity reactions in the context of recent travel and emphasises the importance of early medication review in patients presenting with fever, rash and organ dysfunction.

Fever in the returning international traveler presents a diagnostic challenge in the emergency department due to the wide range of potential infectious diseases that may be encountered abroad, many of which may manifest with nonspecific presentations. Malaria remains the most common and life-threatening tropical cause of fever and must be ruled out in all febrile patients returning from malaria-endemic regions. Other key infections to consider in returning travelers include dengue, enteric fever, and leptospirosis. Early recognition and treatment of these diseases can reduce morbidity and mortality and may help contain disease outbreaks. This review presents a structured, systematic approach to the timely evaluation of fever in returning international travelers, including evidence-based recommendations for the diagnosis and treatment of malaria, dengue, enteric fever, and leptospirosis.

Coccidioidomycosis is endemic to the Western Hemisphere and is rarely encountered in Asia, including Thailand. A detailed history, particularly of prior travel to endemic areas, is critical in refining the differential diagnosis and considering coccidioidomycosis.Here, we report an early adolescent male who presented with fever, non-productive cough and pleuritic chest pain of 1 month's duration. Radiologic findings were suggestive of pulmonary tuberculosis. Antituberculosis therapy was started, but there was no clinical improvement. However, on specific questioning, we learned that he had recently returned from Los Angeles, USA, before the onset of the illness. Hence, pulmonary coccidioidomycosis was suspected based on his travel history to an endemic region and the recognition that its clinical presentation can closely mimic tuberculosis. The diagnosis was confirmed by the results of pathology, cultures and molecular methods of transbronchial lung biopsy specimens. The patient gradually improved after fluconazole treatment.

Leptospirosis is difficult to diagnose because of protean nonspecific clinical manifestations and the lack of rapid, actionable laboratory testing. A previously healthy woman who presented with nausea is described in the present study. She had modestly elevated liver function tests, an unusual pretibial rash, and no fever. She had recently swum in a waterfall in Costa Rica. After the clinicians proposed a leptospirosis diagnosis to the patient, an artificial intelligence program was selected for use by the clinicians to enhance confidence in proposing a rare and unknown diagnosis. The program independently produced a differential diagnosis that led with leptospirosis. Presumptive doxycycline administration led to symptom resolution. Blood (but not urine) Polymerase chain reaction (PCR) test for the LipL32 gene and a novel antibody detection test confirmed leptospirosis. This case represents an unusual clinical presentation of leptospirosis, including the absence of fever, the presence of a pretibial rash, and isolated, mildly elevated bilirubin and transaminases as sole laboratory abnormalities, and highlights difficulties associated with making a rapid, actionable diagnosis.

Relapsing fever is caused by various species of Borrelia bacteria and is traditionally categorized into louse-borne relapsing fever (LBRF) and tick-borne relapsing fever (TBRF). The epidemiological patterns differ according to the vector: LBRF is typically linked to epidemic outbreaks, while TBRF usually presents with an endemic distribution. Even though TBRF is endemic also in the Mediterranean Basin, diagnosis is mainly incidental in migrants or visiting friends and relatives travelling from sub-Saharan Africa. We report a case of TBRF with aseptic meningitis caused by Borrelia crocidurae/duttonii/hispanica in a 46-year-old Senegalese man, diagnosed through blood smear examination performed during the diagnostic workup for malaria. Diagnosis of TBRF is still primarily based on the direct detection of spirochetes in blood smear, although novel molecular methods (PCR) have recently been developed. Awareness, especially in non-endemic areas, and a One Health approach are crucial. Such an approach should aim to monitor the spread of Borrelia species, their vectors, and animal reservoirs, as well as to study their interactions with the environment and climate.

Dengue is not endemic in the continental United States; most cases occur in returning travelers. During August-November 2024, a total of 14 locally acquired cases of dengue were identified in Los Angeles County, California, USA. Epidemiologic evidence indicates that locally acquired cases occurred in several neighborhoods, suggesting short transmission chains after introductions from returning travelers. In one neighborhood, evidence supported ongoing transmission for up to 7 weeks. Median patient age was 54 (range 5-79) years; 8 (57%) patients were female and 6 (43%) male, and 6 (43%) required hospitalization. Delays in healthcare seeking and diagnoses were noted; median time from symptom onset to specimen collection for dengue testing was 9 (range 2-34) days. Local dengue transmission in Los Angeles County highlights the emerging threat of mosquitoborne disease transmission in nonendemic areas and the need for rapid and coordinated public health and vector control responses to interrupt transmission.

Helicobacter pylori (H. pylori) is a bacterial infection with a high prevalence in resource-limited regions. H. pylori infection in children presents with nonspecific and variable clinical features, making diagnosis challenging. We describe a pediatric patient who presented with fever of unknown origin (FUO), anorexia, weight loss, and anemia. Despite an extensive evaluation, the etiology remained unknown until H. pylori testing. This case underscores the importance of including H. pylori in the differential diagnosis of children presenting with FUO, particularly those with recent travel to endemic areas, where exposure to more pathogenic strains may result in significant disease.

Toxoplasmosis remains the most frequent cause of cerebral lesions in patients with acquired immunodeficiency syndrome (AIDS), especially in those not receiving prophylaxis. Medullary involvement, although rare, can cause irreversible neurological damage. When associated with fever in the returning traveler, the etiological diagnosis of spinal cord lesions can be challenging due to the wide range of diagnostic possibilities. We report a unique case of spinal cord toxoplasmosis associated with Salmonella non-typhi bacteremia after a trip to Cameroon, revealing an advanced human immunodeficiency virus (HIV) infection in an otherwise healthy adult male. We also conducted a comprehensive review of reported spinal cord toxoplasmosis cases between the years 2000 and 2025 in both immunocompromised and immunocompetent patients. In our review, paraparesis, sensory loss, and urinary retention were the most frequent clinical presentations (52.17%; 56.52% and 47.84%, respectively), and the majority of the patients had concomitant cerebral lesions (78.26%). Diagnosis remains a challenge, with 48.0% of the reported cases diagnosed through histological detection of the parasite in central nervous system (CNS) tissue. Sulfadiazine-pyrimethamine with additional folinic acid and trimethoprim-sulfamethoxazole (TMP-SMX) remains the treatment of choice for treating cerebral toxoplasmosis in people living with HIV (PLHIV), with no particular recommendation regarding patients with spinal cord involvement. In the reviewed cases, neurological sequelae occurred in 52.2% of patients, and mortality was as high as 30.4%.

Febrile neutropenia (FN) is a medical emergency typically seen in immunocompromised patients with neutrophil counts below 500 cells/µL. It is often associated with chemotherapy, hematologic malignancy, and advanced human immunodeficiency virus (HIV) infection. Severe neutropenia in a low-level viremia and preserved CD4 T-helper cell (CD4) is uncommon and warrants evaluation for alternative etiologies. A 68-year-old man with HIV presented with fever and an absolute neutrophil count (ANC) of zero, without recent chemotherapy or other known myelosuppressive medications. Gram-negative bacteremia was identified, which is often attributed to gut translocation in neutropenic patients. Despite early initiation of tbo-filgrastim, the neutrophil count failed to respond; thus, a bone marrow biopsy was done to evaluate for an underlying marrow disorder. Bone marrow examination combined with genetic and molecular testing revealed a diagnosis of T-cell large granular lymphocytic leukemia (T-LGL), which explained the lack of response to tbo-filgrastim. Because the patient presented with profound neutropenia, gram-negative bacteremia, and a concern of hematologic malignancy, Strongyloides serology was ordered even without known travel or residence in endemic areas, and the result was positive. HTLV-1 serology was also obtained due to its known association with Strongyloides and gram-negative bacteremia, but it returned negative. This case emphasizes the need to broaden the differential diagnosis for severe neutropenia beyond HIV-related marrow suppression. Undiagnosed T-LGL may present with gram-negative bacteremia and failure to respond to granulocyte colony-stimulating factor (G-CSF), and Strongyloides infection should be considered in immunocompromised patients who are being evaluated for occult malignancy, even without identifiable epidemiological risk factors. Early recognition of these conditions can guide timely evaluation and appropriate therapy in complex immunocompromised hosts.

Malaria is an infection caused by one of five species of Plasmodium and is one of the leading causes of fever in the returning traveler.  The Plasmodium species that cause disease in humans are Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, and Plasmodium knowlesi. The infected Anopheles mosquito, most active in the morning and evening, transmits the protozoa to humans. After transmission by an infected mosquito, the Plasmodium sporozoite infects and multiplies within liver cells. These schizonts then get released from liver cells, where they infect red blood cells and again multiply. Clinical disease results from the release of Plasmodium merozoites from the red blood cell. Also, Plasmodium vivax and Plasmodium ovale can remain dormant in the liver (hypnozoites) and can cause disease weeks to years later.[1]   Malaria is endemic to most parts of Africa, South America, East Asia, and parts of Europe and the Middle East. Approximately 125 million visitors travel to these areas, and estimates of malaria infections in travelers range between ten to thirty thousand though the actual number of cases is likely far higher. All travelers to endemic areas should, therefore, receive counseling on areas with a malaria risk, mosquito bite avoidance, and chemoprophylaxis.