Last August, I reported on Mohammad Sajid, a UK citizen who was barred from returning to the US pending several months of background checks - twice. On Monday I got an e-mail from Sajid saying he is leaving his lab in the US, where he works on anti-malarial drugs, to take a job at Leiden University in the Netherlands.

"It's been a really tough choice," Sajid said. "The main reason is the travel. It's as simple as that." When I last spoke to Sajid, he was contemplating returning to the UK when his J1 Visa expired in November. He ended up not going back for fear he could be delayed from re-entering the US a third time. While he continues to work in the US, any travel bears with it the risk of being barred again. "I've been missing [malaria] meetings, important family events. It's just not an option anymore," said Sajid.

Depending on the source, the numbers about whether the US is losing its scientific talent seem conflicted. One recent analysis by the FDA-funded Oak Ridge Institute for Science and Education states that PhDs are leaving the US at a higher rate than earlier in the decade. The number of PhDs who stay in the US for two years after earning their degree dropped from 71% to 66% in 2005. On the other hand, the NSF recently reported that the supply of scientists and engineers in the US continues to grow, and that the unemployment rate in the field is the lowest it's been in years.

Although Sajid has to abandon his projects, he will remain an affiliate member of the Sandler Center for Basic Research in Parasitic Diseases at the University of California, San Francisco. The ironic thing, said Sajid, is that once he leaves the US, he'll be able to return to the US whenever he needs to on a tourist visa.