The fourth case of coronavirus was confirmed in neighboring Sonora, Mexico, on Sunday. The patient is a 22-year-old student who recently returned from Spain, health officials said Sunday.

Gerardo Alvarez Hernandez, Sonora's director of preventative health, praised the young man for isolating himself from others after returning from Spain to his home in the coastal municipality Guaymas.

And as the number of confirmed coronavirus cases in Sonora creeps up, health officials are not only calling on Sonorans to stay home and for all non-essential businesses to close, but also urging anyone arriving to the state to isolate themselves completely.

"We're not going to stop them from coming," Alvarez Hernandez said. "It's not possible and it's not reasonable, epidemiologically speaking. But we are going to protect the vulnerable."

He said anyone traveling to the state — whether Sonorans returning home or visitors — should act responsibly to protect others and "become the vaccine" by staying home in strict isolation.

Sonora’s call for travelers to self-isolate comes just days after the United States and Mexico released an agreement closing the southern U.S. border to all non-essential travel.

Sonora's Health Director Enrique Clausen said Sunday that health officials don't expect any good news in the coming days and weeks. But emphasized the community's role in reducing the number of cases, and preventing an overload of the state's health system.

"One enemy is COVID-19, and the other is irresponsibility," he said. "We're not exaggerating. Stay home and you'll be a hero."

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