Influenza B (Flu B) is a common seasonal respiratory illness. Like other influenza viruses, Flu B primarily spreads through respiratory droplets expelled when an infected person coughs, sneezes, or talks. These droplets can land on surfaces, known as fomites, introducing the concern of indirect transmission. Understanding how long the Flu B virus remains infectious outside the body on these surfaces is important for assessing potential infection risk.
Viability of Influenza B on Common Surfaces
The duration Flu B remains infectious depends heavily on the type of material it lands upon. Non-porous, hard surfaces, such as stainless steel, plastic, and glass, provide a more hospitable environment. Studies indicate that infectious influenza virus particles, including Flu B, can survive on these materials for 24 to 48 hours.
In contrast, porous surfaces like cloth, paper, and cardboard cause the virus to lose infectivity much more rapidly. On these materials, the viable virus typically survives for less than 8 to 12 hours. Even on hard surfaces, the virus’s ability to cause infection decreases significantly over time, with a large percentage of viral particles becoming non-viable within the first few hours. While viral genetic material may remain detectable for weeks, the actual infectivity declines quickly.
Environmental Factors Influencing Viral Lifespan
The survival time of the influenza virus fluctuates based on environmental conditions. Low temperatures generally prolong the viability of the virus on surfaces, while warmer temperatures accelerate the rate of inactivation. This helps explain why influenza seasons often peak in colder months.
Relative humidity also influences survival, with some research suggesting the virus lasts longer in very low humidity. Respiratory secretions, such as mucus or saliva, encapsulate the viral particles and act as a protective barrier. This organic material shields the virus from drying and environmental degradation, extending its lifespan. The initial amount of virus deposited, known as the viral load, also affects survival duration, as a higher concentration enhances survivability.
Understanding Fomite Transmission Risk
While the virus can survive on surfaces for up to a couple of days, this does not automatically translate into a high infection risk. Transmission via a contaminated surface requires the virus to be transferred from the surface to a person’s hand. The contaminated hand must then touch a mucosal surface, such as the eyes, nose, or mouth.
The virus loses infectious capability quickly once transferred to human skin. Studies show the influenza virus remains viable on hands for only about five minutes, creating a narrow window for transmission. Although virus quantities can transfer from a contaminated surface for many hours, rapid inactivation on the skin suggests fomite transmission is less common than direct respiratory droplet spread. The probability of infection relies heavily on the frequency of self-touching and the speed of hand-to-face transfer after contact.
Effective Surface Disinfection Strategies
To mitigate the risk posed by contaminated surfaces, effective and frequent disinfection is recommended. Cleaning should begin with a general household cleaner or detergent to physically remove dirt and organic matter. Following this initial cleaning, an EPA-approved disinfectant effective against influenza A can be used, as these products are also suitable for Flu B.
Common household disinfectants, like a diluted bleach solution (one part bleach to 99 parts water), are effective for general cleaning. For metallic surfaces, a 70% alcohol solution is often preferred to prevent corrosion. Always check the product’s label for the required contact time, which is the duration the surface must remain visibly wet to ensure the virus is killed.
Focusing on frequently touched items is the most practical strategy for interrupting surface transmission. These items include:
- Doorknobs
- Light switches
- Remote controls
- Phones
However, the single most effective action remains consistent and thorough hand hygiene. This includes frequent washing with soap and water or using an alcohol-based hand sanitizer, which directly addresses the critical link in the fomite transmission chain: the contaminated hand.