The virus was not detected in the Western Hemisphere until 1999. Since then, however, more than 3,000 infections have been reported in the United States and more than 200 individuals have died.
संक्रमण झालेल्या लोकांपैकी बहुतेकांना याची जाणीव नसते; केवळ काही जणांत फ्लूसारखी लक्षणे दिसू शकतात.