Chikungunya is a virus that’s spread by mosquitoes. It can’t be passed from person to person. It’s been seen in as many as 60 countries in Asia, Europe, Africa, and the Americas, but chikungunya is rare in the United States. Only 175 cases have been reported here since 2016, and they were all people who’d been to affected areas. Signs of chikungunya usually show up 3 to 7 days after you’re bitten. They typically include fever and joint pain, but you also might have a headache, nausea, or a rash and be very tired. It can be hard to know for sure that you have chikungunya because it can look like other illnesses spread by mosquitoes, such as dengue fever or Zika virus. See your doctor if you have these symptoms and have been somewhere that’s recently had an outbreak. He’ll probably take a sample of your blood to check for signs that your body is fighting off the virus.