The range of Babesia microti (Franca, 1910)-infected ticks is expanding, resulting in locally acquired human babesiosis cases occurring in new areas: Maryland (2009), the District of Columbia (2013), Virginia (2016), and West Virginia (2017). We collected host-seeking ticks from old fields, ecotones, forested habitats and animal hosts in Delaware, Maryland, and Virginia, 2010 to 2024. Ixodes scapularis Say, the tick vector of babesiosis, was captured in all 3 states. PCR revealed B. microti in 2.7% (36/1310) of I. scapularis, with site prevalence ranging from <1% to 12.5% infected. The first B. microti-positive I. scapularis was collected in Northampton County, Virginia, 2012. Of the B. microti-infected ticks, 50% (18/36) were coinfected with Borrelia burgdorferi and one was triple-infected with B. microti, B. burgdorferi, and Anaplasma phagocytophilum. We collected Ixodes keiransi Beati, Nava, Venzal, and Guglielmone ticks from Delaware and Virginia. We found B. microti and B. burgdorferi in those from Virginia, and B. burgdorferi in ticks from a shrew in Delaware. To our knowledge, this is the first report of B. microti and B. burgdorferi-positive I. keiransi from Virginia, and the first report of B. burgdorferi-positive I. keiransi from Delaware. Ixodes keiransi ticks rarely bite humans but are involved in the maintenance and spread of pathogens when sympatric with I. scapularis. We tested a subset of both tick species for Babesia duncani; none were positive. Jurisdictions in the southern mid-Atlantic region should expect babesiosis cases, and Lyme disease and anaplasmosis coinfections, and healthcare providers should consider these tick-borne infections as part of the differential diagnosis.

Heartland virus (HRTV) disease is an emerging tickborne illness in the midwestern and southern United States. We describe a reported fatal case of HRTV infection in the Maryland and Virginia region, states not widely recognized to have human HRTV disease cases. The range of HRTV could be expanding in the United States.

BACKGROUND: Tick-borne encephalitis (TBE) is an arboviral disease that is focally endemic in parts of Europe and Asia. TBE cases among US travellers are rare, with previous reports of only six cases among civilian travellers through 2009 and nine military-related cases through 2020. A TBE vaccine was licenced in the USA in August 2021. Understanding TBE epidemiology and risks among US travellers can help with the counselling of travellers going to TBE-endemic areas. METHODS: Diagnostic testing for TBE in the USA is typically performed at the Centers for Disease Control and Prevention (CDC) because no commercial testing is available. Diagnostic testing for TBE at CDC since 2010 was reviewed. For individuals with evidence of TBE virus infection, information was gathered on demographics, clinical presentations and risk factors for infection. RESULTS: From 2010-20, six patients with TBE were identified. Cases occurred among both paediatric and adult travellers and all were male. Patients were diagnosed with meningitis (n = 2) or encephalitis (n = 4); none died. Cases had travelled to various countries in Europe or Russia. Three cases reported visiting friends or relatives. Activities reported included hiking, camping, trail running, or working outdoors, and two cases had a recognized tick bite. CONCLUSIONS: TBE cases among US travellers are uncommon, with these six cases being the only known TBE cases among civilian travellers during this 11-year period. Nonetheless, given potential disease severity, pre-travel counselling for travellers to TBE-endemic areas should include information on measures to reduce the risk for TBE and other tick-borne diseases, including possible TBE vaccine use if a traveller's itinerary puts them at higher risk for infection. Clinicians should consider the diagnosis of TBE in a patient with a neurologic or febrile illness recently returned from a TBE-endemic country, particularly if a tick bite or possible tick exposure is reported.