JUAREZ, Mexico (Border Report) — Health and safety protocols at migrant shelters will be strictly enforced, following an outbreak of chickenpox that struck more than 70 guests, mostly children, Mexican officials said.

Migrants at the Leona Vicario federal shelter in Juarez began showing signs of illness on Dec. 7 but it wasn’t until earlier this week that victims began to be isolated and new migrants were routed to other shelters, to prevent the spread of the disease, officials said on Friday.

That’s because the illness has a two week incubation period and it’s hard to diagnose at first glance, said Gumaro Barrios, director of the State Health Department in Juarez.

More than 50 children and their families have been placed in isolation and are being “discouraged” from leaving the shelter until the infectious illness, also known as varicella, runs its course. Twenty migrants have already been cleared and some of them have left the shelter. The facility is not taking any new migrants for now and new arrivals are being taken to smaller church-run shelters, officials said.

The way to contain the current spread and prevent further outbreaks not only of chickenpox, but other infectious diseases, at crowded migrant shelters is to encourage frequent hand-washing, covering one’s mouth when sneezing, maintaining clean common areas and being on the lookout for signs of communicable illnesses, Barrio said.

“The most important thing is early detection. How can we detect an illness as soon as possible? The first thing is that relatives take their children to the doctor right away so that he can determine right away if it’s varicella” or another infectious disease, Barrio said. “That way we can issue a (medical) alert promptly.”

The health official said the outbreak appears to be contained now that the sick are isolated and that particular shelter is not taking in new migrants for now. The shelter as of Thursday was housing 811 Central Americans, Mexicans and others who want to file asylum petitions in the United States and are waiting to be called.

Chickenpox is an infectious disease causing a mild fever and a rash of itchy inflamed blisters. It is caused by the herpes zoster virus and mainly affects children, who are afterward usually immune.

Under the Migrant Protection Protocols (MPP) program observed by U.S. Customs and Border Protection, thousands of asylum applicants have been returned to Mexico to wait up to a year for their next appointment. Migrant advocates in El Paso and elsewhere have decried MPP because they say it exposes migrants to crime and other dangers in Mexico.

Barrio said health authorities in Juarez would be paying special attention to “informal data” when it comes to infectious diseases at the shelters. “That informal information will be important to us until we confirm or discard (an outbreak).”

He said health workers would be giving prevention lectures on varicella to the migrants and encouraging all of them to be on the lookout in case one of their peers is sick. He said a doctor visits the shelter twice a day – in the morning and in the afternoon.

News of the outbreak didn’t break until this week and officials from different departments are still putting out contradictory information. On Friday, state officials said 72 people had been affected, but a day earlier a federal official had said there were 74 victims.

Barrio said the information he had was up to date as of Christmas Day. He said all but eight of the victims were children and that most were between 5 and 14.

He added that it would be up to U.S. authorities to determine what to do if a migrant misses an appointment because of illness.