Over the past decade, the prevalence of children identified with autism and autism spectrum disorders (ASDs) has increased in developing countries. In the United States , the prevalence of autism spectrum disorders is now estimated at 1 in 150 children, with some states showing a prevalence as high as 1 in 94.  However, many unanswered questions exist about what is the prevalence of autism in different communities, especially in developing countries, trends in prevalence over time, and what is causing the increase in prevalence.

Determining and monitoring the prevalence over time is challenging, but important given the concerns about increased prevalence. In addition to examining prevalence and trends over time, epidemiologic research is needed to help develop standardized case definitions, help define the features of people with an ASD on a population level, address questions regarding risk factors and causes, and evaluate identification and intervention patterns for people with ASD. Some questions that can be answered using epidemiologic methods, for example include, are some subgroups of the population more affected than others? How do specific genes and the environment interact in terms of causation? Are there public health programs that have unintended consequences, e.g., vaccines? vitamins?.

Autism Speaks and the Centers for Disease Control and Prevention (CDC) are co-sponsoring an initiative to explore possible scientific opportunities in an international collaborative effort in autism epidemiology. The long range objectives of this project are to (1) Develop a network for exchange and collaboration of epidemiology activities across countries; (2) Examine successful international collaborative models applied to other health conditions and identify common features that might facilitate autism surveillance and research; and (3) Identify the unique role that epidemiology can play in understanding the causes of autism; particularly in comparisons across diverse genetic and cultural settings.

There were two meetings in 2005 and 2006 that gathered researchers in autism epidemiology from all over the world to assess interest in forming an international epidemiologic network. On the basis of the interest expressed at these two meetings, we invite researchers who are actively engaged in epidemiologic projects to collaborate with both Autism Speaks/CDC and each other to help address issues that will lead to advancing our understanding of the epidemiology of autism. Further, we are establishing workgroups that focus on the epidemiology of autism based on different types of ascertainment approaches. The three proposed workgroups are:

	Registry systems
	Records or service-based approach
	Developing/low service countries

We encourage you to read each of these approaches to see which best fits your current or proposed research method and population under study and to become active with us by joining one or more of these workgroups. If you decide you would like to participate in our ongoing collaboration you can join the Autism Epidemiology list-serv for periodic updates.