There is now an imminent threat of measles spreading in various regions globally, as the Covid pandemic has led to a steady decline in vaccination coverage and weakened surveillance of the disease, the World Health Organization and the Centers for Disease Control and Prevention said Wednesday.“It is going to be a very challenging 12-24 months trying to mitigate this.”A combination of factors, such as lingering social distancing measures and the cyclical nature of measles, may explain why there has not yet been an explosion of cases despite the widening immunity gaps, but that could change quickly, O’Connor said, pointing out the highly contagious nature of the disease.The United Nations health agency has already seen an increase in large disruptive outbreaks since the start of the year, rising from 19 to almost 30 by September, he said, adding that he was particularly worried about parts of sub-Saharan Africa.Last week, the public health department in Columbus, Ohio, reported a measles outbreak with 24 active cases, according to the NBC News affiliate WCMH.A measles case often starts with a fever, but the illness is typically characterized by a rash that typically begins to spread from the face and neck after a few days."