A "perfect storm" caused by recession, increasingly tight visa regulations and other factors such as concern about swine flu is putting the UK at risk of losing crucial income from overseas students, universities have been warned.
Vice-chancellors and college principals fear that international students may be reluctant to travel to the UK because it is perceived to be difficult to enter and a disease risk.
Last week, the World Health Organisation declared that the swine flu outbreak had become a global pandemic. This means that the swine flu virus is now spreading in at least two regions of the world. Infection rates are rising in the UK, Australia, Japan and Chile, among other countries.
There are concerns that this change of status and the widespread media coverage of the issue, particularly in Asia, may result in overseas students failing to take up their places at British universities in September.
Malcolm Gillies, vice-chancellor of City University London, said he was most worried about the response of students from countries that had not yet been affected by the virus.
One danger, he said, is that students' sponsors may withdraw funding to restrict travel; another is that students may be barred from leaving the country altogether.
"There is a tendency to close borders, and that's a natural response if you don't have much of a disease and everyone else has," he said. "It's clearly a problem that we've got these external issues, because they compound a number of internal hits that we're taking in terms of reductions in (state) funding."
Professor Gillies, whose university has a high proportion of foreign students, said he would be watching Australia to monitor the extent of the problem.
As Australia is now in its winter, swine flu is incubating in the country and the number of reported cases more than quadrupled in just one week at the end of May.
"It will be fascinating to see what the response to that in the Asian student market is," he said. "Australia will be the first testing point."
James Pitman, UK managing director of Study Group, which brings international students to the country, said the combination of problems constituted a "perfect storm" for UK higher education. "It's all building up to make the UK a less attractive destination," he said.
Mr Pitman agreed that the media coverage devoted to swine flu was a major recruitment risk. "Officials in China have advised people not to send their children abroad," he said.
He also predicted that the "cost and complexity" of the new student visa system would have an adverse impact.
For a student from Hong Kong, he said, it now takes 15 rather than five days to process a student visa application, which may hold up their arrival and enrolment.
"The more barriers you put up, it's inevitable that some of them are going to say, 'I haven't got the time for that,'?" Mr Pitman said.