This marks South Dakota as the 33rd state to confirm a case, with the total number of cases reported across the country reaching at least 1,088.

According to the South Dakota Department of Health, the infected individual is an adult from Meade County who had recently traveled abroad. This case arises as federal health officials urge all Americans to ensure they are vaccinated against measles before international travel, following updated guidance from the Centers for Disease Control and Prevention (CDC). The previous advice was limited to travelers heading to regions with ongoing outbreaks.

The CDC emphasizes that the measles, mumps, and rubella (MMR) vaccine, which is a standard part of the immunization schedule, offers up to 97% effectiveness after two doses. The agency recommends that adults who lack immunity through previous infection or vaccination should get vaccinated.

This year, at least 62 U.S. residents contracted measles while on airplanes, with only one case involving in-flight transmission, as per a CDC spokesperson.

In South Dakota, the infected individual visited two medical facilities, potentially exposing others to the virus. Health officials are alerting the public to the early signs of measles, which appear in two stages. Initial symptoms include a runny nose, cough, and slight fever, accompanied by red, light-sensitive eyes, with the fever escalating daily. The second stage, appearing three to seven days later, features a high fever of 103 to 105 degrees Fahrenheit and a red blotchy rash that starts on the face and spreads to the rest of the body.

Dr. Joshua Clayton, state epidemiologist, emphasized the highly contagious nature of measles, which spreads through the air from an infected person. Those without immunity, either through vaccination or past infection, are at significant risk if they come into contact with the virus.

Health officials advise that the best defense is vaccination. Immunity is typically assured for those born before 1957, those who have received the MMR vaccine (one dose as adults or two doses as children and high-risk adults), those with confirmed measles antibodies, or those who have recovered from a confirmed measles infection.

The MMR vaccine is generally administered to children between 12 to 15 months of age, followed by a second dose at four to six years old. For international travel, vaccinations can begin as early as six months.

More details about measles, including comprehensive fact sheets and a dedicated webinar for healthcare providers, can be found on the Department of Health's website.