In an interview with Sky News, The University and College Union (UCU) says the government and universities are risking public health by pushing on with plans to fully reopen campuses in a few weeks' time.
The start of a new university year is "the biggest migration of people on an annual basis in the UK," Jo Grady, UCU general secretary, says. "That's a million students, moving across country, cycling in and out of lockdown zones, of bubbles, of homes, into new cities, where we are not track and tracking those students, we are not testing those students," she said.
"We are seriously concerned that if the government and universities do not step in and discourage this... we could see universities becoming the care homes of the second wave of COVID-19."
The UCU wants, at the very least, for the government to enforce mandatory COVID-19 testing of students on arrival. But some staff who work in universities believe that student numbers should be restricted altogether.
"It's not worth the risks of coming in for face-to-face teaching," university research fellow Eric Lybeck told Sky News.
"There are some exceptions I can see where lab facilities are needed, or disadvantaged students might not have access to the internet or certain health concerns where perhaps some access to university facilities could be provided.
"But wherever young people can do their seminars, small group teaching, lectures online it just seems that that is the right thing to do until the government gets a handle on the pandemic."
Following the changes to the A-level results, many universities reported having to accept more students than they had initially accounted for, complicating existing social distancing plans. The UCU says the government should financially back institutions that "do the right thing by public health" and move services online, so that they avoid loss of income through missed tuition and accommodation fees.
It has been a torrid summer for this year's cohort of freshers, who have had exams cancelled, grades remarked and university places awarded and taken away. James Appiah, 18, who is set to start at the University of Cambridge next month, said restrictions on joining his classmates would "ruin the expectation I have of going to Cambridge".
He added: "I expect to see my lecturers face-to-face, go and have a good time with my friends, to network with people. "Online learning is not exactly a big loss, I believe it'll only be for the first year, as long as there is not a second wave of the coronavirus, but [if I stayed at home] I'd be very upset about it."
The Department for Education says that "we are confident that universities are well-prepared for the return of students."
"The safety and well-being of university staff and students is always our priority," it adds. "We are keeping our guidance under constant review, and are currently updating our advice... including on face coverings."