An immigration expert and critic of the Obama administration’s immigration policies said Thursday that the Liberian man who fell ill with ebola this week after arriving in Dallas, should not have been issued a visitor’s visa because he presented a high risk of remaining in the United States illegally.

The expert also called on Washington to follow the example of Kenya and several other African countries, which have recently banned all visitors from Liberia and other countries affected by the outbreak of the ebola virus.

Other immigration experts disagreed with both assessments, however, saying the current U.S. visa screening process has been made extremely rigorous in the past decade and that international health agencies oppose shutting down travel to and from the ebola-stricken region.

Meanwhile, officials in Liberia said Thursday that the patient, Thomas Eric Duncan, will be prosecuted when he returns home for lying on his airport exit-screening form when asked if he had been in contact with anyone infected with ebola.

Jessica Vaughn, a researcher affiliated with the nonprofit Center for Immigration Studies in Washington, said U.S. officials had made one “mistake” by issuing Duncan a visa last year and a second error by allowing him to enter the country.

“If you look at his circumstances, it should have been really tough for him to qualify for a visa,” Vaughn said. She noted that Duncan reportedly was single, jobless, living away from his home country and had a number of relatives in the U.S. — all factors that often indicate a person is unlikely to return home after their visa expires. “He clearly appears unqualified.”

Efforts to seek comment from federal immigration officials were unsuccessful, but a former senior immigration official from the Clinton administration said that procedures for issuing visitor visas have been strengthened since the terrorists attacks of 2011 and are now “state of the art.”

“These decisions are made on the totality of information about a person. It is a highly professional function that was dramatically revamped after the lapses that preceded 9/11,” said Doris Meissner, who headed the federal immigration agency in the 1990s and is now a senior fellow at the Migration Policy Institute in Washington.

Vaughn also pointed out that Liberians have an extremely high rate of “visa overstays” — higher than all other countries except Cuba, Burundi, Eritrea and the Democratic Republic of Congo. In 2012, she said, the Department of Homeland Security reported to Congress that 148 visiting Liberians had remained in the U.S. illegally.

In the past five years, the number of Liberians issued U.S. visitors’ visas has risen sharply. Last year about 3,500 were granted to Liberians, and a total of about 13,500 were granted to people from the three ebola-stricken countries — Liberia, Guinea and Sierra Leone.

Vaughn also said that even if Duncan has legal permission to visit the U.S., he and other recent visitors from ebola-affected countries should be undergoing more rigorous screening by U.S. officials when they arrive.

“Other countries are banning travellers from outbreak countries, and we should, too,” she said. Under U.S. law, officials have the right to ban anyone from entering the country if they present a potential threat to public health or safety. “In the middle of a health crisis, the government should be setting up more robust screening protocols,” she said.

Meissner disagreed, noting that the World Health Organization and other health agencies have said that closing borders and banning travel can be counterproductive because they “weaken the ability to mobilize and respond” to a health crisis.

On Wednesday, White House spokesman Josh Earnest said there was no need for a travel ban and that administration officials are “confident” that government medical experts are doing what is needed to contain the virus. “We can stop the spread of ebola in its tracks,” he said.

Certain emergency protocols have been put in place since the ebola outbreak, including extra screening for passengers leaving on flights from Liberia and the other affected countries.

However, press reports Thursday from Liberia said that Duncan had reportedly answered “no” to a question about whether he had cared for an ebola patient or touched someone who had died from ebola. He also showed no symptoms at the time.

Duncan reportedly helped carry a sick woman to a taxi a few days before he left the country, but it was not clear at the time whether she had contracted the virus. Liberian airport officials were quoted as saying that Duncan would be prosecuted and that he and other infected travellers had brought a “stigma” on Liberians living abroad.

Several Liberian community leaders in the Washington area said that some Liberians living in Dallas and elsewhere might be reluctant to come forward with information related to visitors or other sources of infection, because they did not have legal permission to remain in the U.S. and feared they might be deported.

However, the State Department, which issues visitors’ visas, has already taken steps to defer any deportations of Liberians currently in the U.S., in order to make sure they are protected from contracting the virus if returned to their homeland.