A surge in influenza B cases is providing a lesson to California residents that they cannot let down their guard just because influenza A activity declines.
The H3N2 strain of influenza A grabbed headlines early in the flu season, as Californians learned anew of its deadly force, but now influenza B is causing a growing number of flu outbreaks in the Golden State.
“It’s often the case where influenza A starts off the flu season, and then as the season goes on, influenza B becomes more important,” said Dr. Dean Blumberg, an expert in infectious diseases at UC Davis Health. “Influenza A caused almost all the influenza starting at the beginning of this season in 2017, and then once 2018 started, influenza B started causing a greater proportion of illnesses.”
For the week ending Mar. 10, influenza B caused the prevailing number of cases – 72 percent – tested in sentinel labs reporting to the California Department of Public Health. Nationally, influenza B was found in 53.5 percent of cases that same week, the CDC reported.
The increased prevalence of influenza B is particularly bad news for the state’s children, said Blumberg, chief of pediatric infectious diseases at the medical center, because it’s been shown that they are 20 percent more likely to die from influenza B than from the A strains.
So far this season, 128 children nationwide have died of flu, 17 of them in the region that includes California, Nevada and Arizona. It is the largest number of children to perish since 148 died in the 2014-15 season.
Parents are often shocked that their children have died of an illness that many people recover from within a few days, said Blumberg, but pediatric patients can have a number of complications with influenza.
They can get adult respiratory distress syndrome, an over-the-top inflammatory response that makes it difficult for children to breathe, Blumberg said. They end up on bypass machines to try to provide them oxygen and sometimes those measures just don’t work.
Influenza also can compromise children’s immune systems and leave them vulnerable to co-infections such as the antibiotic-resistant staph infection commonly known as MRSA.
Pronounced MUR-suh, the acronym stands for methicillin-resistant staphylococcus aureus. The bacteria involved are resistant to not only methicillin but also amoxicillin, penicillin and oxycillin. Blumberg said MRSA can cause overwhelmingly destructive pneumonia that can kill lung cells.
It’s not too late to get a flu vaccine, Blumberg said, and he urged expectant mothers to do so. The immunities are passed on to the unborn child, he said, and study after study has shown the vaccine poses no risk to the pregnancy or the fetus.
“Influenza vaccine in childhood doesn’t start until six months of age,” he said. “The kids less than six months of age actually have one of the highest rates of hospitalization due to influenza, and we can’t vaccinate them to protect them because the vaccines aren’t approved for use at that age.”
Although the number of flu deaths had been declining in California since the week of Feb. 3, they rose sharply last week to 14 from four in the prior week, according to state public health officials. And Kinsa, a company that tracks reports of fever through its smart thermometers, found that 3.15 percent of Sacramento County residents reported fevers during that week, compared with 2.89 percent the prior week. Such increases are a reminder not to grow complacent, Blumberg said.
He recommended: If you are sick with flu, stay at home for at least two days after symptoms have subsided. Use an alcohol-based hand sanitizer, or wash your hands regularly to prevent the spread of germs. And, when sneezing or coughing, cover your mouth with the crook of your arm rather than with your hands.
Also, he noted, having one type of influenza does not protect you from getting another type.
“It’s like when you have a cold,” Blumberg said. “The common causes of cold, there are more than 100 strains of those. You can certainly get more than one in a season, and it’s the same with flu. I think parents are going to be most familiar with this because children who attend day care will get around 10 respiratory illnesses per year.”