SAN DIEGO — A fourth flight filled with migrants who entered the U.S. illegally through Texas arrived in San Diego on Friday. The latest flight left Brownsville, Texas, in the morning, stopped in El Paso and reached San Diego International Airport in the afternoon.  

Last week, the U.S. Border Patrol started a new program to ease the border backlog in the Rio Grande Valley by sending three flights a week west to San Diego. 

Many of the detainees are from Honduras, El Salvador and Guatemala. They cross into Southern Mexico and go north on two routes. San Ysidro is perceived as the safer, but geographically further path. The route to McAllen, Texas, is considered more dangerous but is a shorter distance and lately has seen an overwhelming number of migrants. 

RELATED: Second plane with migrants from Texas lands in San Diego

Border Patrol says San Diego is capable of processing more people so they are flying them here. The people that arrived in San Diego on Friday were caught recently, given a quick medical screening and put on a plane. From the airport, authorities said the migrants would get processed at a border patrol station with a second medical check. 

Within 72 hours the group is turned over to Immigration and Customs Enforcement. If they want asylum then they usually end up at a shelter created by San Diego County, but health officials there say they are seeing an outbreak of the flu. 

A shelter in Texas recently stopped processing detainees because of a flu outbreak there. The Border Patrol tells News 8 they don't let anyone board a flight if they're showing symptoms. They sent the following statement: 

"The family units are pre-screened in Rio Grande Valley for health concerns prior to being assigned to flights. If they present any symptoms of illness, they will not be placed on a flight, but rather will be provided medical treatment. If no symptoms of illness are present, they will be assigned to a flight.  

Upon arrival in San Diego, the individuals are screened again for health concerns. If an individual is presenting symptoms of an illness at this second screening, the Border Patrol then seeks the necessary proper medical care.  

It is possible that detainees may not immediately show symptoms of illness prior to getting on a flight.  Agents closely monitor all movement and conditions of the detainees in our custody."

RELATED: San Diego County health officials confirm flu outbreak at local migrant shelter

Still, local leaders say the federal government should do more and pay more. 

"I am extremely frustrated at the lack of the ability of our federal government to step up and do its job and assume full responsibility for what they should be doing,” said San Diego County Supervisor Dianne Jacob. 

RELATED: Beyond the Border: News 8 takes an in-depth look at life where the U.S. and Mexico meet

Border Patrol says the Texas flu outbreak isn't impacting flights to San Diego, which are set to continue indefinitely. 

"The cost to county government is in the neighborhood of $2-million and that number is growing each day,” said Jacobs.

Many have asked reached out to News 8 to ask what happens to the migrants once they are in San Diego or if the migrants will be staying here. Officials say the migrants seeking asylum will stay in local shelters pending court appearances, but that doesn't mean they will stay here. They are usually sent to sponsors or families across the country within two days.

News 8's Brandon Lewis explains more of what is true and what isn't in this VERIFY report: