Influenza, commonly called the flu, is a respiratory illness caused by a virus that primarily targets the nose, throat, and lungs. It typically spreads person-to-person through respiratory droplets expelled when an infected individual coughs or sneezes. Transmission can also occur indirectly when these droplets land on objects (fomites) that are then touched by a healthy person who subsequently touches their face. This potential for surface transmission raises questions about how long the influenza virus remains viable in environments related to food.
How Long the Flu Virus Remains Viable on Food
Scientific research has not extensively focused on the precise duration the influenza virus remains infectious when deposited directly onto various types of food. The risk of contracting the flu directly from consuming contaminated food is generally considered low, particularly if the item is cooked. The primary concern in a food-handling environment relates more to the contamination of kitchen surfaces and food packaging.
Studies examining viral viability focus on common kitchen surfaces, such as plastic and stainless steel. Hard, non-porous surfaces are known to support the virus for the longest periods, with influenza A and B viruses detectable for up to 24 to 48 hours after contamination. More recent studies clarify that the actual time the virus remains infectious is often much shorter than the detection window.
The infectious influenza A virus is typically recovered from non-porous surfaces for up to four hours, and rarely longer than nine hours, depending on the viral strain and environmental factors. Porous materials, such as cloth, paper towels, and cardboard packaging, tend to inactivate the virus more quickly. On these absorbent surfaces, the infectious window is significantly reduced, often lasting less than 8 to 12 hours. The virus degrades quickly outside a host organism, even though genetic remnants may be detectable for longer periods.
Conditions That Affect Viral Survival
The survival time of the influenza virus depends highly on the environmental conditions surrounding the contaminated surface. Temperature is a major factor, as the virus is sensitive to heat, which rapidly breaks down its protective outer layer. Heat quickly inactivates the virus; for example, temperatures used in milk pasteurization (63° C/145° F and 72° C/162° F) eliminate viral infectivity within seconds to minutes.
Conversely, colder temperatures prolong the virus’s lifespan, which is a reason flu season often coincides with winter months. The virus can persist longer in cool, refrigerated environments, although its infectious capability still diminishes over time. Humidity also plays a role; low humidity often allows viral droplets to remain suspended as aerosols for longer, while very high humidity causes larger droplets to settle quickly. The surface material matters, as non-porous surfaces offer a more stable environment for viral particles compared to porous surfaces, which accelerate inactivation by absorbing moisture.
Reducing Transmission Risk Through Food Handling
The most effective strategy to prevent flu transmission through food handling is focusing on proper hygiene and preparation techniques. Rigorous hand washing with soap and water for at least 20 seconds is the single most important step for anyone preparing food. This action physically removes viral particles acquired from touching contaminated surfaces or from respiratory droplets.
Individuals experiencing flu symptoms, such as fever, cough, or body aches, should strictly avoid preparing food for others to eliminate the risk of contamination. Routinely cleaning and disinfecting high-touch kitchen surfaces, like countertops, cutting boards, and appliance handles, helps break the chain of transmission from fomites.
The influenza virus is easily killed by heat. Cooking food to recommended internal temperatures provides a safeguard against potential contamination. For instance, cooking poultry to an internal temperature of 74° Celsius (165° Fahrenheit) or ground meat to 71° Celsius (160° Fahrenheit) ensures any potential virus is inactivated.