Adults can contract Influenza B, a common respiratory virus that circulates annually. It can cause significant illness, impacting people of all ages. Understanding its characteristics, symptoms, and prevention is helpful.
Key Characteristics of Influenza B
Influenza B is a single-stranded RNA virus primarily known to infect humans, though it can also affect ferrets, pigs, and seals. This limited host range distinguishes it from Influenza A, which infects a wider variety of animals. Unlike Influenza A, Influenza B typically mutates at a slower rate, which contributes to its lower likelihood of causing pandemics.
Despite its slower mutation rate, Influenza B can still cause considerable illness and mortality globally. While historically observed more frequently in children, adults are susceptible to Influenza B infections. This virus often circulates later in the flu season compared to Influenza A, with its prevalence varying by year and region. Globally, Influenza B accounts for approximately 23% of reported influenza cases.
Transmission of Influenza B occurs mainly through respiratory droplets expelled when an infected person coughs, sneezes, or talks. These droplets can land in the mouths or noses of nearby individuals or be inhaled. Indirect transmission is also possible by touching contaminated surfaces and then touching one’s own mouth, nose, or eyes. Individuals can be contagious starting about one day before symptoms appear and for up to five to seven days after becoming sick.
Symptoms and When to Seek Medical Attention
Symptoms of Influenza B in adults typically appear suddenly. Common indicators include fever, chills, body aches, and headaches. Respiratory symptoms such as a cough, sore throat, and a runny or stuffy nose are also present. Fatigue is common, sometimes accompanied by nausea, vomiting, or diarrhea, though gastrointestinal issues are more frequently observed in children.
Seek medical attention if severe symptoms occur. These include a high fever exceeding 103 degrees Fahrenheit (40 degrees Celsius), difficulty breathing, persistent chest or abdominal pain or pressure, sudden dizziness, or confusion. Severe or persistent muscle pain and a significant decrease in urination are also concerning signs. Prompt medical evaluation is recommended for individuals with underlying health conditions, such as asthma, heart disease, or diabetes, pregnant individuals, or those over 65, due to their increased risk of complications.
Diagnosis and Treatment Approaches
Diagnosing Influenza B in adults typically begins with a healthcare professional reviewing symptoms and conducting a physical examination. To confirm the virus, a mucus sample is usually collected from the nose or throat using a swab. Several types of tests can be performed on this sample.
Rapid antigen detection tests (RIDTs) provide quick results, often within 15 to 30 minutes, by detecting specific viral proteins. However, these tests may not be as accurate as molecular tests. Molecular assays, such as polymerase chain reaction (PCR) tests, are more sensitive and specific, detecting the virus’s genetic material. PCR test results can take several hours to a few days and can differentiate between Influenza A and B viruses.
Treatment for Influenza B generally involves managing symptoms, including rest, adequate fluid intake, and over-the-counter medications for fever, pain, and cough relief. For some individuals, prescription antiviral medications may be considered. Common antiviral drugs include oseltamivir, zanamivir, peramivir, and baloxavir marboxil. These medications are most effective when started within 48 hours of symptom onset, as they can help reduce illness severity and duration by approximately one day and may prevent complications. Antivirals are recommended for individuals at high risk of complications, those with severe illness, or hospitalized patients, even if treatment is initiated beyond the 48-hour window.
Preventing Influenza B
Annual vaccination is one of the most effective ways to prevent Influenza B. The seasonal flu vaccine protects against the most common circulating influenza strains, typically including both Influenza A and B. Historically, quadrivalent flu vaccines have protected against two Influenza A and two Influenza B lineages. However, the B/Yamagata lineage may have become extinct, potentially leading to future vaccines targeting fewer B strains.
In addition to vaccination, practicing good hygiene habits can reduce the risk of contracting and spreading Influenza B. Regular handwashing helps remove viruses from surfaces or direct contact. Covering coughs and sneezes with a tissue or into the elbow helps contain respiratory droplets.
Avoid close contact with sick individuals. If experiencing flu-like symptoms, stay home from work or public gatherings, especially until 24 hours after a fever has subsided, to protect others. Avoid touching your face, particularly the mouth, nose, and eyes, after touching potentially contaminated surfaces.