Citizens of certain countries that participate in the US Visa Waiver Program (VWP) do not need a visa to travel for business or tourism, which includes attending conferences such as ICDX.
Please consult the website above regarding the requirements to visit the United States under the VWP. Although you may not need a visa, you still must have authorization through the Electronic System for Travel Authorization (ESTA). Please review the information on that website and make sure you complete your application and receive the authorization prior to boarding a US bound carrier. The US Customs and Board Patrol (CBP) recommends that you apply for your ESTA at the time you book your travel, but no less than 72 hours prior to boarding. Once approved, an ESTA is valid for two years from the date of authorization (or until your passport expires) and can be used for multiple entries as long as valid, but only for a total of 90 days.
If you are not a citizen or national of one of the countries that participates in the "Visa Waiver Program, you will need to apply for a nonimmigrant visa for your travel to the US. Most business and tourism travelers need a B-1 or B-2 visitor visa. The B-1 classification is most typical for conference attendees.
Although the process may vary depending on the US Embassy or Consulate where you apply, in general you will need:
Please consult the web page for Visas and Visiting the US.