Influenza B is a common seasonal respiratory illness caused by an influenza virus that primarily infects the nose, throat, and sometimes the lungs. This type of flu is highly contagious and contributes to annual flu epidemics, particularly during colder months. While similar to Influenza A in symptoms, Influenza B is distinct as it is known to infect humans and certain other mammals, but not as wide a range of animals as Influenza A, which impacts its mutation rate.
Main Ways Influenza B Spreads
Influenza B primarily spreads through respiratory droplets expelled when an infected person coughs, sneezes, or talks. These droplets, larger than 10 micrometers, can travel a short distance and land on the mucous membranes of another person’s nose or mouth, leading to infection.
The virus can also be transmitted through smaller airborne particles, often referred to as aerosols, which are less than 5 micrometers in diameter. These tiny particles can remain suspended in the air for extended periods and travel further than larger droplets, potentially reaching deeper into the respiratory tract when inhaled. Airborne transmission contributes significantly to household spread.
Contact transmission represents another pathway for Influenza B spread, occurring in two main forms: direct and indirect. Direct contact involves touching an infected person and then touching one’s own eyes, nose, or mouth. Indirect contact, also known as fomite transmission, happens when an individual touches a surface or object contaminated with the virus and subsequently touches their face. The influenza virus can survive on certain environmental surfaces for a period, facilitating this mode of transmission.
Key Factors in Transmission
The incubation period for Influenza B, the time from exposure until symptoms begin, typically ranges from one to four days. An infected individual can transmit Influenza B to others even before symptoms manifest, often starting about one day prior to feeling sick. People are generally considered most contagious during the first three to four days after their symptoms begin. The period of contagiousness can extend up to five to seven days for adults, and sometimes longer for young children or individuals with weakened immune systems.
Environmental conditions and social interactions also influence transmission. Crowded indoor environments with poor ventilation can facilitate the spread of Influenza B, as they increase the likelihood of close person-to-person contact and exposure to respiratory particles. Some individuals can be infected with Influenza B and spread the virus without ever developing symptoms, contributing to its spread.
Reducing the Risk of Spread
Annual vaccination is a primary method for reducing the risk of contracting and transmitting Influenza B. The flu vaccine is updated yearly to target the most common circulating strains, offering protection against the virus and reducing the severity of illness if infection occurs. Getting vaccinated also helps protect those around you, including individuals who cannot receive the vaccine.
Practicing consistent hand hygiene significantly lowers the chance of spreading Influenza B. Washing hands thoroughly with soap and water for at least 20 seconds is effective in removing the virus. When soap and water are unavailable, an alcohol-based hand sanitizer with at least 60% alcohol can be used to reduce viral load on the hands. It is particularly important to clean hands after coughing, sneezing, or touching frequently used surfaces.
Adopting proper respiratory etiquette helps contain the spread of respiratory droplets. This involves covering coughs and sneezes with a tissue, then disposing of it immediately, or coughing and sneezing into the elbow if a tissue is not available. Avoiding touching the eyes, nose, and mouth with unwashed hands prevents the transfer of the virus from contaminated surfaces to the respiratory system.
Minimizing close contact with sick individuals and staying home when ill are important measures to prevent onward transmission. Individuals with Influenza B should stay home until at least 24 hours after their fever has resolved without the use of fever-reducing medications. Regularly cleaning and disinfecting frequently touched surfaces, such as doorknobs, light switches, and electronic devices, can also reduce the presence of the virus in the environment.