Whooping cough is a rather mild-sounding name for a disease that can kill a baby before it’s even diagnosed.

Ten infants in California have died since the first of the year in an outbreak of whooping cough, whose proper medical name is pertussis. Many Americans think of it as a disease of the past, but nearly 6,000 cases in California and more nationwide suggest otherwise.

Although California has had the highest number of whooping cough cases this year, other states are seeing slight increases. And Michigan has been watching a rise since the second half of 2008, which continues, according to the CDC. By Aug. 15, Michigan had seen 610 pertussis cases, compared with 902 for all of 2009 and 315 cases in 2008.

Daryl and Felicia Dube of Lancaster, South Carolina, became all-too familiar with the disease this year. Their baby son, Carter, came down with pertussis in January.

Whooping cough explained

Carter, just 5 weeks old, developed a low-grade fever one day and was unusually fussy but didn’t show any other obvious symptoms, said Felicia Dube, 35. She called the family’s pediatrician, who told her it was probably nothing serious but had her bring him in that same day to be sure. At the office, the doctor became concerned about the baby’s rapid breathing and called an ambulance to take him to a hospital in Charlotte, North Carolina, about 30 miles away.

Things only got worse at the hospital over the following days as Carter’s eyes rolled around, he grew weak and irritable and he refused to eat. His heart started racing but his blood pressure was puzzlingly low.

Then the coughing started.

“This may sound strange, but the sound of it was like listening to a man, a smoker, cough,” Felicia Dube said.

Listen to what whooping cough sounds like

Carter was coughing so hard that it would make his feet come up in the air. It hurt and made him cry, which made him cough more, his mother said.

When the infant could not catch his breath and turned blue, he was rushed to the pediatric intensive care unit and given a high concentration of oxygen. Test results hadn’t come back yet , but doctors believed he had pertussis and aggressively treated him with antibiotics and sedatives.

“He wasn’t responding to anything,” Dube said.

After several frustrating days as Carter got worse and worse, surgeons hooked him up to a respirator. When that didn’t help, surgeons implanted an extracorporeal membrane oxygenation (ECMO) machine, which takes over the work of the heart and lungs. Large tubes came out of Carter’s neck, routing his blood through a bedside machine.

“They tried to prepare us for it, but you’re not prepared to see that,” Dube said. “… Once they did that to him, we couldn’t touch him, so I couldn’t hold him.”

WATCH: Why it's important to protect against pertussis

And it wasn’t enough. Nine days after coming down with a 100.1-degree fever, Carter Dube died. Lab tests finally confirmed the pertussis diagnosis two days later.

“They did everything they could for him,” his mother said of the doctors and staff at Levine Children’s Hospital in Charlotte. “They tried. They cried as hard as we did.”

At 5 weeks, Carter was too young to have received his first pertussis vaccination. Because bad weather had kept the family from traveling since he was born, the infection only could have come from the parents, 10-year-old brother, Zach, or the pediatrician’s office, Dube said.

“It’s a horrible guilty feeling as his mother – I’m the one who’s supposed to protect him, and I could have been the one who gave it to him,” she said. “… That’s something you just don’t shake.”

Dube has become an advocate for adult pertussis booster shots to protect babies through what’s known as “cocooning.”

Why are parents skipping vaccines?

“Nobody should have to watch what we watched,” she said.