As the annual tick season approaches in North America, a rare but dangerous virus is attracting mounting attention: Powassan virus. While this tick-borne illness remains uncommon, recent research and rising case reports point to growing concerns that reverberate beyond Western borders—and carry valuable warnings for Thailand as well.
Powassan virus, primarily transmitted by blacklegged ticks, has been recognized as one of the most serious tick-borne diseases in the United States, despite its rarity. Last year, Minnesota reported a record 14 cases, the highest count since 2008 when official recordkeeping began. According to Minnesota Department of Health data, while most years saw fewer than five cases, a slow but concerning uptick has prompted both local and national action. “The risks are relatively low, however, all the tick prevention that you would do to keep yourself from getting one of those more common diseases will also help keep you safe from getting Powassan,” Elizabeth Schiffman, an epidemiologist supervisor at the Minnesota Department of Health, emphasized in a recent interview (Star Tribune).
Why should Thai readers pay attention? Thailand, like many tropical countries, faces a rising tide of tick-borne and other vector-borne diseases—an issue compounded by climate change and increased human encroachment on forests. The emergence of Powassan virus in North America mirrors the global trend of new and old vector diseases appearing in fresh hotspots. With Thailand already combating familiar threats like dengue and Japanese encephalitis, awareness of Powassan provides a crucial case study in both public health preparedness and the importance of international surveillance (ScienceDirect Topics; MDPI).
Though often asymptomatic or mild (manifesting as fever, headache, vomiting, or weakness), Powassan infection can—especially in the elderly or the immunocompromised—cause devastating neurological symptoms, including seizures, brain swelling, and sometimes death. According to research and case reports, approximately 1 in 10 patients with severe symptoms dies, and survivors may face lingering issues such as chronic headaches and memory problems (PubMed Case Report). Notably, the virus is named after the Canadian town where it was first identified, and like Thailand’s focus on local names for infectious diseases, this reflects the intertwined relationship between geography and virus emergence (Wikipedia).
The surge in cases prompted the U.S. National Institutes of Health to fund a major new study led by Dr. Matthew Aliota of the University of Minnesota. He will investigate the virus in two American epicenters, Minnesota and New York, with the goal of uncovering why Powassan is spreading and how best to combat it. Dr. Aliota remarked, “The Powassan virus is… an understudied virus. It’s one more thing on the list of reasons why you should be diligent in terms of taking precautions to prevent tick bites” (Star Tribune).
Despite interest from global health scientists, data scarcity remains a challenge: the virus is detectable in blood for only about a week after infection, making diagnosis difficult and likely leading to underreporting. As Schiffman notes, “One of the reasons there are so few cases and that we don’t know as much about it as we do some of the other infections people get is because testing isn’t widely available for Powassan. I think there’s probably a lot of people that could have it, especially in those mild cases, and they’re not ever getting it detected and reported."
For Thais, this scenario is all too familiar. Difficulties in detecting emerging viruses—especially in early stages or mild cases—remain a challenge in the surveillance of diseases such as scrub typhus, leptospirosis, and zoonotic influenzas. Moreover, global warming is expanding the territory of ticks and their viral passengers, as seen in the steady geographical expansion of both Powassan and established Asian tick-borne illnesses (MDPI; Mahidol Review PDF).
What is especially worrisome about Powassan virus is its capacity to cause encephalitis—potentially lethal brain inflammation—even though no specific antiviral treatment or vaccine exists. Treatment is supportive only, and the best defense remains tick-bite prevention. The U.S. Centers for Disease Control and Prevention (CDC) advises wearing long-sleeved clothes and pants, applying permethrin repellents, and checking the body carefully for tiny blacklegged ticks after exposure to grass, brush, or woodland (Wikipedia). In Thailand, where rural communities, trekkers, and agricultural workers regularly encounter similar tick species, these global recommendations should be adapted to fit local habits. For example, while som tum and other outdoor picnics may be quintessentially Thai, enjoying them in forested areas without protective clothing or repellents can raise the risk of tick exposure.
Internationally, fewer than 70 Powassan virus cases are reported annually, but this is almost certainly an undercount. Since 2010, the U.S. CDC has logged about 194 cases, 22 of which were fatal (PubMed Case Report). With the same underdiagnosis challenge applicable to diseases in Thailand, the Powassan case reminds us to maintain vigilance even toward rare infections.
From a Thai perspective, the risk of Powassan itself is extremely low—so far, it is found only in North America and parts of Russia. No cases have been reported in Thailand or Southeast Asia (ScienceDirect Topics). However, the greater lesson is in preparedness and prevention. Thai public health authorities are encouraged to continue robust surveillance not just for known tick-borne pathogens (such as spotted fever, anaplasmosis, or babesiosis), but also be ready to adapt to “imported” vector-borne diseases in an era of climate and ecological change (Mahidol Review PDF).
Historically, Thailand has adapted global health lessons by tailoring interventions to local realities—from mosquito net campaigns for malaria to dengue warning system rollouts in schools. The story of Powassan virus provides another opportunity: strengthening tick-borne disease prevention and clinical education, even for conditions rare or absent here, builds resilience for future public health threats.
Looking forward, experts anticipate that new tick-borne viruses could emerge or spread to regions where populations lack prior immunity. Thailand, with its rich forests, booming ecotourism, and increasingly mobile population, must maintain readiness against these “one health” challenges that bridge animal, human, and environmental health.
For practical action, Thai readers can take several steps: protect against tick bites when visiting forests, parks, or rural fields by wearing covered clothing and using proven repellents; check skin and clothing after outdoor activities; and seek prompt medical evaluation for unexplained fevers, headaches, or neurological symptoms following likely tick exposure. Communities and schools can raise awareness with simple “look and remove” campaigns modeled on global best practices.
ที่สำคัญที่สุด—prevention is always better than cure, especially with “mystery” viruses that have no treatment or vaccine. While Powassan virus is not an immediate concern for Thailand, its story offers valuable lessons in the interconnections of global public health, the unpredictability of emerging diseases, and the age-old wisdom of being prepared. Stay informed, stay protected, and enjoy nature with eyes wide open.
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