WASHINGTON (Reuters) – A U.S. intelligence report warned Americans Tuesday they were under growing threat from infectious diseases brewing in the rest of the world.

“Senior policymakers are becoming increasingly concerned about the implications of growing infectious disease threats for U.S. citizens at home and abroad, for U.S. armed forces deployed overseas,” said John Gannon, chairman of the National Intelligence Council.

He released a new National Intelligence Estimate report, “The Global Infectious Disease Threat and Its Implications for the United States,” at a symposium at the Smithsonian Institution.

Asia was likely to see a major increase in infectious disease deaths driven by the spread of HIV and AIDS, replacing Africa as the epicenter of the disease before 2015, he said.

At least 30 previously unknown diseases have appeared globally since 1973, including HIV, AIDS, Hepatitis C, Ebola hemorrhagic fever and the encephalitis-related Nipah virus that emerged in Indonesia last year, Gannon said. “Many are still incurable,” he added.

Twenty well-known infectious diseases such as tuberculosis, malaria, and cholera have reemerged or spread since 1973, some reappearing in “deadlier, drug-resistant forms,” Gannon said.

Americans were at risk because the United States was a major hub of global travel, immigration and commerce and had a large civilian and military presence overseas, the report said.

Infectious diseases killed at least 170,000 Americans a year and were “likely to continue to account for more military hospital admissions than battlefield injuries,” the report said.

At highest risk will be U.S. military forces deployed in humanitarian or peacekeeping operations in developing countries, the report said.

The probability of a “bioterrorist attack” against Americans was likely to grow as more countries and groups developed biological warfare capability, the report said.

“Although there is no evidence that the recent West Nile virus outbreak in New York City was caused by foreign state or non-state actors, the scare and several earlier instances of suspected bio-terrorism showed the confusion and fear they can sow regardless of whether or not they are validated,” the report said.

An outbreak of West Nile-like virus killed five people and made 50 ill in New York last year. The virus is common in parts of Africa and Asia but had never before been reported in the United States.

“Many infectious diseases — most recently, the West Nile virus — originate outside U.S. borders and are introduced by international travelers, immigrants, returning U.S. military personnel, or imported animals and foodstuffs,” the report said.

The National Intelligence Council provides analysis on national security issues as part of the U.S. intelligence community under CIA Director George Tenet.