Imported neurologic infections remain a surveillance concern: full analysis

Version 2

A review in Brain and Nerve revisits a persistent challenge for countries with otherwise strong infectious disease control: neurologic infections acquired abroad can still arrive with returning travelers. Author Hiroyuki Murai argues that, in Japan, imported mosquito-borne diseases deserve particular attention, using dengue fever as a key example and contrasting it with Japanese encephalitis, whose domestic incidence has dropped markedly after broad vaccine uptake. (niid.go.jp)

That framing fits Japan’s longer surveillance history. Imported dengue has been tracked for years through national reporting systems, with earlier analyses showing that many cases were associated with travel to South and Southeast Asia. More recent Japanese surveillance summaries continue to monitor imported dengue trends, reflecting how international travel can repeatedly reintroduce exposure risk even in places without sustained endemic transmission. Japan’s experience with Japanese encephalitis has moved in the opposite direction: vaccination, alongside broader public health changes, has substantially reduced human disease burden. (pubmed.ncbi.nlm.nih.gov)

The source article’s main message is straightforward: favorable sanitary conditions alone don't eliminate the risk of neuroinfectious disease when pathogens are acquired overseas. Dengue remains globally widespread, and WHO reported unprecedented transmission levels in 2024, adding to the relevance of travel-associated case surveillance. Murai’s emphasis on bite prevention is consistent with public health guidance, because dengue is transmitted by mosquitoes and prevention still depends heavily on avoiding exposure. For Japanese encephalitis, the Ministry of Health, Labour and Welfare continues to stress vaccination and public education, reflecting the disease’s continued importance despite low incidence. (who.int)

Additional background from the literature reinforces why neurologic infection remains central to this discussion. Japanese encephalitis is the most common vaccine-preventable cause of mosquito-borne encephalitis in Asia and the western Pacific, and severe cases can leave lasting neurologic sequelae in survivors. Clinical reviews also note that there is no specific antiviral treatment, making prevention especially important. That helps explain why Murai’s contrast between imported dengue risk and reduced Japanese encephalitis incidence is useful: one disease illustrates the ongoing pressure of travel-linked importation, while the other shows what sustained immunization policy can achieve. (ncbi.nlm.nih.gov)

Direct expert reaction to Murai’s article was limited, but the broader field has been consistent on the key themes. Reviews of Japanese encephalitis describe the disease as a major regional neurologic threat where transmission persists, and emphasize mosquito surveillance, vaccination, and ecological monitoring. Research on vertebrate hosts also underscores that Japanese encephalitis virus is best understood through a One Health lens, because transmission depends on interactions among mosquitoes, animal hosts, and human exposure. (pmc.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals, this is less a story about a single paper than a reminder about imported disease intelligence. Vector-borne neurologic pathogens can move with people, animals, and insects, and their relevance to veterinary medicine often lies in ecology, surveillance, and prevention rather than direct companion-animal caseload. Japanese encephalitis virus, for example, involves animal hosts in its transmission cycle, which means changes in mosquito activity, livestock management, wildlife interfaces, or regional climate conditions can matter to both animal and human health. Veterinary teams may not diagnose these infections routinely, but they are part of the professional network that notices unusual vector pressure, educates pet parents about bite prevention during travel, and contributes to local awareness of emerging infectious threats. (pmc.ncbi.nlm.nih.gov)

The dengue angle also matters because imported arboviral disease is no longer a niche issue. WHO’s 2024 update described global dengue activity at unprecedented levels, and public health agencies in multiple countries have reported increases in travel-associated cases. For veterinary readers, that broader trend is a signal to keep imported vector-borne diseases on the radar, especially when discussing travel, relocation, or climate-sensitive disease risk with pet parents and colleagues in public health. (who.int)

What to watch: The next signals to monitor are updated Japanese imported-case surveillance, regional mosquito activity, and any changes in travel-associated dengue patterns that could alter risk communication for both human and animal health professionals. (id-info.jihs.go.jp)