A large population survey in England finds many adults with undiagnosed autism, bringing the disorder’s prevalence in adults to 1 in 100, approximately the same rate as in children, according to a report in May in the Archives of General Psychiatry.

The first comprehensive autism study in South Korea has found that the prevalence of the disorder is more than double the number in the United States.

Two large studies published in the past two months have found that traits linked to autism are widely distributed in the general population. Although about 1 in 100 children is diagnosed with autism, up to 30 percent of people may have at least one of the traits associated with the disorder.

A child in Australia is more likely to have autism if he or she is the first-born, is born to a woman who is older than 40 years, or belongs to a family of higher socio-economic status, according to a study published in March in PLoS One.

Short questionnaires that parents can fill out at a pediatrician’s office flag early signs of autism in infants and toddlers well before the disorder is usually diagnosed, according to two new studies.

Cultural stigma, lack of awareness about mental health and poor medical infrastructure have led to inaccurate diagnoses and artificially low autism prevalence in many countries around the world, epidemiologists say.

The new edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM) won’t be published for another two years, but changes proposed to the diagnostic criteria for autism are already sparking heated debate.