SOUTH FORSYTH — The Forsyth County school system is reporting that a third-grader at Sharon Elementary has been diagnosed with measles. In an email sent Wednesday to parents of the 1,063 students at the school on Old Atlanta Road, Principal Amy Bartlett wrote that officials “do not mean to cause alarm but want to keep all of [you] informed when a case has been reported.” Citing student and health care confidentiality laws, Forsyth County Schools spokeswoman Jennifer Caracciolo said officials could not provide additional details. She did note, however, that this is a rare circumstance for the school system and may be the first case in as many as 15 years. According to the district’s website, all children entering the school system are required to have been vaccinated for measles, among other diseases. The school system is not releasing whether the student had the measles vaccine or received a waiver for immunizations. And it was not immediately clear how he or she may have contracted the highly infectious disease. While measles is probably best known for the full-body rash it causes, the first symptoms are usually a hacking cough, runny nose, pink eye and a high fever. According to Bartlett’s email, the rash reportedly appears first on the forehead, and then spreads down over the face, neck and body to the arms and feet. Parents whose children develop any of the above signs and symptoms are directed to contact their health care provider. In her email, Bartlett notes that measles is “primarily transmitted from person to person by large respiratory droplets.” According to the email, “Following exposure, more than 90 percent of susceptible people develop measles. The virus can be transmitted from four days before the rash becomes visible to four days after the rash appears. The first symptom is usually fever. The measles rash appears two to four days after the fever begins.”