Jessica Berman writes at the Voice of America:

A team of scientists, whose work was published in the journal Proceedings of the National Academy of Sciences, has found that a specific strain of the HIV virus passed from Haiti to the United States in about 1969 before spreading further.

The strain, called subtype B, predominates in the United States, Europe, large parts of South America, Australia and Japan. The team traced the virus by examining archived blood samples from five early AIDS patients - all of them Haitian immigrants to the United States - and analyzed genetic sequences from another group of patients from around the world.

Using the data, they developed a map of the virus, which they believe shows conclusively that the strain came to the United States via Haiti, probably by a single person, in around 1969.

Some questions that can't really be properly analyzed today in academe: How would the US HIV epidemic be different if US immigration laws hadn't been loosened in the 60's?

Did expansion of immigration in the 60's accelerate the spread of new diseases in the US?

What limits on immigration, tourism and business travel are appropriate to control spread of communicable diseases-particularly ones that are poorly understood?