"Any rumors that they are bringing Ebola or are at risk of Ebola are patently false," a Texas city official said.

Joe Raedle / Getty Images Migrants wait to be loaded onto a bus by US Border Patrol agents after being detained in El Paso, Texas.

Baseless rumors that asylum-seekers crossing the southern border were infected with the Ebola virus gained so much traction on social media this week that officials in Texas held a press conference Tuesday to dispel the fake reports.

Rumors about people from the Congo infected with the potentially deadly virus had been circulating on social media for days from prominent conservative, alt-right, and white supremacist figures. On Tuesday, officials from the city of San Antonio addressed the misinformation. This was after unsubstantiated reports suggesting that Ebola-infected immigrants were roaming the city's streets were published on the conspiracy theory websites Infowars and Gateway Pundit. "This is a little bit much ado about nothing," said Colleen Bridger, interim assistant city manager and director of the San Antonio Metropolitan Health District. "Any rumors that they are bringing Ebola or are at risk of Ebola are patently false." About 250 family units seeking asylum from Central Africa have crossed the southern US border near San Antonio since June 4, Bridger said, including immigrants from the Congo and Angola. None of them have exhibited any signs of the virus or been flagged for the virus during their health screenings, she said. The rumor quickly spread Monday after the Alex Jones–owned outlet Infowars claimed in a headline, "U.S. Cities Overwhelmed With Numbers of Illegal Migrants Arriving From Ebola-Stricken Countries." An Infowars reporter also went to a temporary immigrant shelter set up in San Antonio to follow up on rumors about the virus. The reporter turned on their camera inside the shelter, against a request of those running the center, and was removed after getting into a "kerfuffle," Bridger said.

Eric Gay / AP An asylum-seeker peers out the door at a makeshift resource center in downtown San Antonio.

The Infowars reporter questioned Bridger on camera and suggested that immigrants could carry the Ebola virus for months on their person without becoming infected themselves or displaying any signs of the disease, which she explained was not possible.

The incubation period for the virus is 21 days, Bridger said, and most of the people traveling from Central Africa have been traveling for months through South America after leaving Africa. "Someone with the virus would develop symptoms of that disease within 21 days of that exposure," she said in the press conference. "So if you do the math and think of the fact that they left their country many, many months ago, there's no possibility that these individuals are bringing Ebola into our country." Many of the immigrants have been screened after crossing different borders, and they are screened once again by US Border Patrol, she said.

But that hasn't stopped conspiracy theorists and far-right figures from spreading the false rumor. David Duke, a white supremacist and a former Grand Wizard of the Ku Klux Klan, tweeted a link falsely claiming that San Antonio was "Under Siege by Ebola Refugees."

And last month, Brian Kolfage, the decorated Iraq War veteran leading a viral effort to crowdfund and build a private wall on the southern border, claimed that a "DHS insider" told him that there were nine "confirmed" Ebola cases at the US border. Kolfage tweeted again to his 72,000 followers on June 5 that 150 Africans had crossed the border and "10 tested positive for #Ebola." But US Customs and Border Protection said the claim was false. "There have been no encounters of Ebola along the southwest border," an agency spokesperson told BuzzFeed News.

🚨 🚨 🚨 .@WeBuildtheWall was just informed from a second highly trusted source that of 150 Africans that have recently arrived here at least 10 tested positive for #Ebola. Think what you want, but these are people who know the facts because they work along side it.