SAN DIEGO (Border Report) -- The state of Baja California has detected 40 new cases of whooping cough in the city of Tijuana, most of whom are children who have not been immunized against the bacterial disease, health officials say.

"Tijuana is a such a big and congested city, this is why you see so many cases here," said Adrián Medina Amarillas, Baja's health secretary.

He added that said whooping cough is especially hard and potentially deadly on children.

"This is a warning to all parents to make sure their children are vaccinated," he said.

Baja's health secretary said there seems to be a whooping cough outbreak about every four years.

"We're on alert because when you least expect it, it will happen, and we can't confuse it with the flu or covid, although the symptoms are very similar. ... We're notifying doctors to be pay close attention."

Whooping cough is brought on by the Bordetella pertussis bacteria that is prone to infect children. It can be deadly if not treated early.

"Compared to 2022 and 2023, we've seen a huge increase in cases this year, this is a serious condition especially in children who are a year old or younger," Medina Amarillas said.