Disease Alerts

Comments: Since the last situation report (11/24/2025), there has been one (1) new confirmed positive equine premises identified in Arizona (Santa Cruz County - new affected county). All confirmed cases in the 2025 outbreak have been vesicular stomatitis New Jersey virus (VSNJV) serotype. Updates are as follows: Arizona • Cochise County – no new positive premises • Gila County – no new positive premises • Santa Cruz County (New Affected County) – 1 new confirmed positive equine premises. Premises that have diagnostic laboratory confirmation of VSV are categorized as confirmed positive premises. Once a county is confirmed as VSV-positive, new equine premises presenting with clinical signs of VSV in that county are not required to be tested for confirmation of the disease, but the premises will be quarantined and classified as a presumptive positive premises. Premises may also be classified as presumptive positive if clinical animals on the premises fail to meet confirmed case definition, but there is diagnostic laboratory evidence of recent VSV infection. United States Department of Agriculture Animal and Plant Health Inspection Service. Vesicular stomatitis virus circulates annually between livestock and insect vectors in southern Mexico and only occasionally results in incursion to the U.S. when climatic and ecological factors support movement of VSV-infected insect vectors northward.;

Number Confirmed: 1; 
Comments: Since the last situation report (10/31/2025), there has been one (1) new confirmed positive equine premises identified in Arizona (Gila County - new affected county). All confirmed cases in the 2025 outbreak have been vesicular stomatitis New Jersey virus (VSNJV) serotype. Updates are as follows: Gila County (New Affected County) - 1 confirmed positive equine premises • Since the last situation report (10/31/2025), the following previously confirmed positive premises were released from quarantine on 11/12/2025: 2 premises in Cochise County. Premises that have diagnostic laboratory confirmation of VSV are categorized as confirmed positive premises. Once a county is confirmed as VSV-positive, new equine premises presenting with clinical signs of VSV in that county are not required to be tested for confirmation of the disease, but the premises will be quarantined and classified as a presumptive positive premises. Premises may also be classified as presumptive positive if clinical animals on the premises fail to meet confirmed case definition, but there is diagnostic laboratory evidence of recent VSV infection. Vesicular stomatitis virus circulates annually between livestock and insect vectors in southern Mexico and only occasionally results in incursion to the U.S. when climatic and ecological factors support movement of VSV-infected insect vectors northward. For more information, go to https://www.aphis.usda.gov/sites/default/files/vsv-sitrep-11-24-25.pdf;

Number Confirmed: 2; 
Number Exposed: 60; 
Facility Type: Private Facility; 
Comments: On October 31, 2025, the National Veterinary Services Laboratories in Ames, Iowa, confirmed findings of vesicular stomatitis New Jersey virus (VSNJV) in horses on two separate premises in Cochise County, Arizona. One (1) horse, a 21-year-old grade mare, on the first premises met confirmed vesicular stomatitis virus (VSV) index case definition with compatible clinical signs and viral genome sequence data indicative of VSNJV on swabs from oral lesions. There are an additional 52 horses and 120 cattle on the first premises which are not clinically affected. On a second premises in Cochise County, Arizona, one (1) horse, an 8-year-old Quarter Horse gelding, met confirmed VSV index case definition with compatible clinical signs and viral genome sequence data indicative of VSVNJ on swabs from oral lesions. There are an additional 6 horses and 60 cattle on the second premises which are not clinically affected. These two premises are the 2025 VSV index cases for the United States.

The last outbreak of VSV in the U.S. occurred from May 2023 through January 2024 with a total of 319 premises affected in 3 states (California, Nevada, and Texas). Vesicular stomatitis virus circulates annually between livestock and insect vectors in southern Mexico and only occasionally results in incursion to the U.S. when climatic and ecological factors support movement of VSV-infected insect vectors northward.

Known competent vectors for transmission of VSV include black flies, sand flies, and biting midges (Culicoides spp.). The initial epidemiological investigations on both VSVconfirmed positive premises in Cochise County, Arizona, indicate that incursion of VSVinfected insect vectors is the likely source of infection on these premises. There have been no recent livestock movements on or off either premises. Biosecurity measures and vector mitigation on the affected premises have been instituted to reduce within-herd spread of the virus. The susceptible livestock species are being monitored and both VSV-positive premises will remain under state quarantine until 14 days from the onset of lesions in the last affected animal on the premises. 

For more information, go to https://www.aphis.usda.gov/livestock-poultry-disease/cattle/vesicular-stomatitis