In the realm of influenza, flu A and flu B stand as the prevalent strains that spread among humans. As the United States navigates through the current flu season, a surge in reported cases is observed nationwide. Distinct variations exist between these flu strains. The country is firmly entrenched in the midst of flu season, as data from the Centers for Disease Control and Prevention (CDC) reveals that a significant 29% of flu tests have yielded positive results, while close to 7% of medical visits are linked to respiratory illnesses. While experiencing the flu is challenging under any circumstance, it is crucial to recognize the two major strains: flu A and flu B, each with unique characteristics.
“Both strains are currently circulating, with flu A strains being the dominant force,” notes Dr. William Schaffner, an infectious disease expert and professor at Vanderbilt University School of Medicine.
Introducing the experts: Dr. Thomas Russo, professor and chief of infectious disease at the University at Buffalo in New York, and Dr. William Schaffner, an infectious disease specialist and professor at Vanderbilt University School of Medicine.
A nationwide flu activity map indicates that the majority of states are grappling with “high” or “very high” levels of flu activity. Essentially, the flu is widespread. Here’s a breakdown of what distinguishes flu A from flu B.
What sets flu A apart from flu B?
According to Dr. Thomas Russo, professor and chief of infectious disease at the University at Buffalo in New York, flu A and flu B are distinct strains of influenza. While there are four types of flu—A, B, C, and D—A and B are the primary strains driving each year’s flu season, as outlined by the CDC.
A quick note: Infections caused by flu C generally result in mild illness and are not associated with seasonal epidemics. On the other hand, flu D viruses mainly affect cattle.
Dr. Russo highlights that flu A circulates in both humans and animals, whereas flu B is predominantly a human-related disease.
Influenza A viruses are categorized into subtypes based on two surface proteins—hemagglutinin and neuraminidase, resulting in 29 different subtypes and over 130 subtype combinations. Notably, the prevalent influenza A subtypes among people are A(H1N1) and A(H3N2), states the CDC.
On the other hand, flu B viruses are not subcategorized but are classified into two lineages—B/Yamagata and B/Victoria, according to the CDC. These viruses evolve at a slower rate compared to flu A viruses. Dr. Russo points out that one of the lineages (B/Yamagata) has not been detected since March 2020.
Generally, flu B tends to cause localized outbreaks, while flu A is known for sparking epidemics, explains Dr. Schaffner. He adds, “Flu
Doctors explain that it is impossible to differentiate between flu A and flu B based solely on symptoms. However, a flu test conducted at your healthcare provider’s office can identify the specific strain you are infected with. It is important to note that if there is a prevalent presence of either flu A or flu B in your locality and you happen to contract the virus, chances are high that you have been affected by the dominant strain. Moreover, in the event of developing a more severe illness, the likelihood increases that you are dealing with flu A rather than flu B.
When it comes to treatment, both flu A and flu B are managed similarly. According to Dr. Schaffner, antiviral medications such as Tamiflu are effective against both strains. Another newer antiviral, baloxavir marboxil (Xofluza), has also shown promising results in combating the flu. Nevertheless, these treatment options are not flawless, with symptom alleviation possibly occurring just a day earlier at best, as stated by Dr. Russo. Supportive care, including adequate rest, hydration, and the use of over-the-counter fever reducers like acetaminophen or ibuprofen as necessary, can contribute to making you feel more comfortable while recovering from the flu.
In terms of prevention, getting the annual influenza vaccine is the most effective way to shield yourself against both flu A and flu B, advises Dr. Russo. The vaccine’s efficacy in preventing the virus varies each year, depending on its composition. Each vaccine is tailored to target specific strains of the flu virus, typically including at least one strain of flu A and one strain of flu B. For instance, this year’s flu vaccine safeguards against two strains of flu A and one strain of flu B, as per the CDC. Dr. Russo highlights that the vaccine’s effectiveness can fluctuate annually, with some years showing better matches for flu A compared to flu B, and vice versa.
If you have not yet received your flu shot, Dr. Russo recommends promptly scheduling an appointment for vaccination. Given the current high prevalence of the flu, he emphasizes that it is crucial to act swiftly. “It’s not too late to get vaccinated,” he stresses, as the flu season is expected to persist for some time.
