The Indian Ocean Lineage (IOL) of the chikungunya virus (CHIKV) East/Central/South African (ECSA) genotype, which originated in Kenya, spread to the Indian ocean and the Indian subcontinent, and then expanded through Southeast Asia in the previous decade. It carried an adaptive mutation E1-A226V, which enhances CHIKV replication in Aedes albopictus. However, the IOL CHIKV of the most recent outbreaks during 2016–2020 in India, Pakistan, Bangladesh, the Maldives, Myanmar, Thailand, and Kenya lacked E1-A226V but carried E1-K211E and E2-V264A. Recent CHIKV genome sequences of the Maldives and Thailand were determined, and their phylogenetic relationships were further investigated together with IOL sequences reported in 2004–2020 in the database. The results showed that the ancestral IOLs diverged to a sub-lineage E1-K211E/E2-V264A, probably in India around 2008, and caused sporadic outbreaks in India during 2010–2015 and in Kenya in 2016. The massive expansion of this new sub-lineage occurred after the acquisition of E1-I317V in other neighboring and remote regions in 2014–2020. Additionally, the phylogenetic tree indicated that independent clades formed according to the geographical regions and introduction timing. The present results using all available partial or full sequences of the recent CHIKVs emphasized the dynamics of the IOL sub-lineages in the Indian subcontinent, Southeast Asia, and Eastern Africa.

In recent decades, chikungunya virus (CHIKV) has become geographically widespread. In 2004, the CHIKV East/Central/South African (ECSA) genotype moved from Africa to Indian ocean islands and India followed by a large epidemic in Southeast Asia. In 2013, the CHIKV Asian genotype drove an outbreak in the Americas. Since 2016, CHIKV has re-emerged in the Indian subcontinent and Southeast Asia. In the present study, CHIKVs were obtained from Bangladesh in 2017 and Thailand in 2019, and their nearly full genomes were sequenced. Phylogenetic analysis revealed that the recent CHIKVs were of Indian Ocean Lineage (IOL) of genotype ECSA, similar to the previous outbreak. However, these CHIKVs were all clustered into a new distinct sub-lineage apart from the past IOL CHIKVs, and they lacked an alanine-to-valine substitution at position 226 of the E1 envelope glycoprotein, which enhances CHIKV replication in Aedes albopictus. Instead, all the re-emerged CHIKVs possessed mutations of lysine-to-glutamic acid at position 211 of E1 and valine-to-alanine at position 264 of E2. Molecular clock analysis suggested that the new sub-lineage CHIKV was introduced to Bangladesh around late 2015 and Thailand in early 2017. These results suggest that re-emerged CHIKVs have acquired different adaptations than the previous CHIKVs.

Climate change has led to an increase in average global temperatures, with the last 8 years being the warmest on record. Global temperatures have risen significantly over the past two decades, compared to the average temperature during 1910–2000 (https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/global/time-series). Asia has experienced the highest increase at 1.78°C per century, followed by Europe at 1.51°C ( Figure 1). The United Nations World Meteorological Organization recently reported that the probability of El Niño developing this year is growing. ¹ El Niño is an irregularly occurring climate pattern of unusual warming of sea surface temperatures in the central and eastern tropical Pacific Ocean, occurring every 2–7 years. ¹ El Niño can disrupt normal weather patterns globally, and is forecasted to drive global temperatures even higher than the already occurring human-induced warming from greenhouse gases. ¹ In combination with El Niño, 2023 and 2024 are predicted to be amongst the warmest years in almost two centuries. Tropical regions appear to be significantly impacted, with several countries in South America, South and Southeast Asia, Southwestern Europe and Northern Africa experiencing summer temperatures that exceed 35°C and can easily surpass 40°C. The extreme heat effects of El Niño have already been witnessed this year with record shattering temperatures recorded this April in Peru, Spain, Portugal, Morocco and Algeria. As a result, the impact of heat on health is unavoidable for both locals and travellers, particularly those travelling to hot climate destinations who are not acclimatized.

Artesunate is the drug of choice for treating patients with severe malaria. Post-artesunate delayed hemolysis (PADH) is an uncommon adverse event from malaria treatment. Most patients with PADH are non-immune travelers. The pathophysiology of PADH is not fully understood, but the most likely mechanism is “pitting”, in which red blood cells carrying dead parasites killed by artesunate’s action are directed to the spleen for clearing the dead parasites. After the cleansing process, these red blood cells re-enter the circulation but with a smaller size and impaired integrity, resulting in a shortened lifespan of 7–21 days. Therefore, most patients with PADH usually present with clinical features of hemolytic anemia 7 days or later after the initiation of artesunate. To date, the benefits of artesunate treatment outweigh its adverse events, and no fatal cases have resulted from PADH. However, the hematological follow-up of patients with malaria treated with artesunate is recommended for clinicians to detect any delayed hemolytic event early and prevent potentially serious consequences.

Chikungunya virus is an Alphavirus belonging to the family Togaviridae that is transmitted to humans by an infected Aedes mosquito. Patients develop fever, inflammatory arthritis, and rash during the acute stage of infection. Although the illness is self-limiting, atypical and severe cases are not uncommon, and 60% may develop chronic symptoms that persist for months or even for longer durations. Having a distinct periodical epidemiologic outbreak pattern, chikungunya virus reappeared in Thailand in December 2018. Here, we describe a cohort of acute chikungunya patients who had presented to the Bangkok Hospital for Tropical Diseases during October 2019. Infection was detected by a novel antigen kit and subsequently confirmed by real-time RT-PCR using serum collected at presentation to the Fever Clinic. Other possible acute febrile illnesses such as influenza, dengue, and malaria were excluded. We explored the sequence of clinical manifestations at presentation during the acute phase and associated the viral load with the clinical findings. Most of the patients were healthy individuals in their forties. Fever and arthralgia were the predominant clinical manifestations found in this patient cohort, with a small proportion of patients with systemic symptoms. Higher viral loads were associated with arthralgia, and arthralgia with the involvement of the large joints was more common in female patients.

Background: Drug tourism reflects the expanding illicit drug market, posing health risks in unfamiliar travel settings. Existing knowledge specifically addressing substance use among international travellers is sparse and has not been reviewed to date. This review aimed to describe the recreational substance abuse in international travellers. Methods: A literature search was conducted on PubMed, Google Scholar and Scopus using keywords related to recreational substances and international travellers. A total of 11 021 articles were reviewed, charted and summarized for the evidence on prevalence, patterns and characteristics of substance abuse and their health- and non-health-related problems on international travellers. Results: A total of 58 articles were included. Most were cross-sectional studies and review articles. In total, 20 articles addressed the prevalence of substance abuse in travellers, 33 looked at characteristics and patterns of substance abuse in travellers and 39 investigated the health- and non-health-related problems from substance abuse. Estimated prevalence of recreational substances abuse varied from 0.7% to 55.0%. Rates of substances abuse were 9.45–34.5% for cannabis, 20.4–35.9% for alcohol intoxication, 2.82–40.5% for MDMA, 2–22.2% for cocaine, 2–15% for psychedelic agents and 2% for methamphetamine. The prevalence varied according to travellers’ characteristics and travel destinations. Direct health problems included neuropsychiatric problems. Indirect problems included accident and unintentional injuries, crime and violence, risky sexual behaviours and sexual violence and blood-borne infections. Non-health-related problems included air rage, deportation and violation of local laws. Conclusion: Substance abuse among international travellers is an underestimated problem that requires intervention. These findings emphasize the importance of addressing this issue to mitigate both health and well-being problems among travellers whilst promoting safer and more responsible travel experiences. In the context of travel health practices, practitioners should counsel travellers whose itineraries may include substance abuse, informing them about associated risks and consequences.