There have been 137 cases of clinical West Nile virus (WNV) infection detected in horses from 11 States.

The horses are from:

• 1 county in Alabama: Dale (Ozark, 2);
  
• 2 counties in Connecticut: Hartford (West Granby, 1) and New London (Stonington, 1);
  
• 18 counties in Florida: Alachua (Alachua, 1), Baker (Glen St. Mary, 1; Sanderson, 1), Clay (Maxville, 2; Middleburg, 1), Duval (Jacksonville, 2), Flagler (Bunnell, 1), Gadsden (Havana, 2; Quincy, 1; city not reported, 1), Hamilton (Jennings, 1), Holmes (Bonifay, 1), Jefferson (Greenville, 2; Lamont, 1; Monticello, 27; city not reported, 3), Leon (Tallahassee, 15), Madison (Greenville, 3; Lee, 1; Madison, 1; Pinetta, 1), Marion (Citra, 1), Nassau (Callahan, 1; Hilliard, 1; city not reported, 1), St. Johns (Elkton, 1; St. Augustine, 1; city not reported, 1), Suwannee (Branford, 2; Lake City, 1; Live Oak, 5; O’Brien, 1; Wellborn, 2), Taylor (Greenville, 1; Lake Butler, 1; Perry, 8; Shady Grove, 2), Wakulla (Crawfordville, 4; Woodville, 1), and Walton (DeFuniak Springs, 1);
  
• 3 counties in Georgia: Brooks (Quitman, 1; Boston, 1), Clinch (Homerville, 1), and Lowndes (Valdosta, 4);
  
• 1 county in Kentucky: Bourbon (Paris, 1);
  
• 1 parish in Louisiana: Vermilion (Abbeville, 1; Erath, 1; Kaplan, 1);
  
• 1 county in Massachusetts: Plymouth (Carver, 1; Halifax, 1; Lakeville, 1; Middleboro, 5)
  
• 2 counties in New Jersey: Burlington (Mt. Laurel, 1) and Monmouth (Allentown, 1);
  
• 1 county in New York: Suffolk (Hauppauge, 1; Kings Park, 1; city not reported, 1);
  
• 2 counties in Pennsylvania: Bucks (Bensalem, 1) and Montgomery (Huntingdon Valley, 1); and
  
• 2 counties in Virginia: Madison (Brightwood, 1) and Rockingham (Dayton, 1).

At least 28 (20 percent) of the 137 horses died or were euthanized. The numbers of equine deaths associated with WNV infection by State are: Connecticut, 1; Florida, 19; Georgia, 2; Louisiana, 1; Massachusetts, 1; New Jersey, 1; New York, 2; and Virginia, 1.

Of the 137 horses, 135 were positive on a WNV IgM-capture enzyme-linked immunosorbent assay (MAC-ELISA) and a WNV plaque reduction neutralization test (PRNT) performed on serum at the National Veterinary Services Laboratories (NVSL) in Ames, Iowa. One of the other two horses had brain tissue that tested positive at the NVSL on WNV reverse transcriptase-nested polymerase chain reaction (RT-nPCR), had serum that was positive on WNV PRNT, and had WNV isolated from brain tissue. An additional horse was positive on WNV RT-nPCR on a virus isolate submitted to the NVSL for confirmatory testing