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How Does the Flu Spread?

The flu is an uncomfortable, oftentimes severe and sometimes deadly virus. It is characterized by fever, sore throat, cough, runny nose, body aches, chills, headaches, fatigue and sometimes nausea and vomiting. Most people recover within a week of the initial onset of symptoms. Others, however, may grow progressively worse and develop complications of the virus, the most common of which is pneumonia. Though not always the case, individuals who develop complications typically have compromised immune systems.

Regardless of which camp you typically fall into, and regardless of the strength of your immune system, getting the flu is never fun. Ideally, you will prevent it from spreading around your home and community in all the ways you know how. Aside from getting your annual flu shot, effective flu prevention begins with understanding how the virus spreads in the first place.

How the Flu Spreads

The flu spreads in two main ways: via airborne droplets or aerosols and through contact. Below are overviews of how the virus spreads in these ways.

How the Flu Spreads Through the Air

The most common way people contract the flu virus is by breathing in particles that are floating through the air. Once we breathe them in, the particles coat and infect the lining of our respiratory tract, which include the mouth, nose, throat and lungs. The air becomes contaminated with flu particles when an infected person sneezes, coughs or even breathes.

The flu, along with other respiratory viruses, can spread in the air in two ways:

  • Droplets: Droplets are small beads of mucus or saliva that contain the flu virus. Infected persons launch droplets into the air when they sneeze, cough or speak. Because droplets are typically much heavier than aerosols, they do not stay in the air for very long. For instance, once a person coughs out saliva, the saliva typically falls quickly to the ground or another surface. Though the droplets themselves are still contagious, there is little chance they will enter the nose or mouth of a nearby person.
  • Aerosols: Aerosols are infected particles that enter the air when we breathe. Aerosols are much lighter than droplets and, therefore, can remain floating in the environment for hours.

Despite the fact that aerosols remain in the environment for longer, most experts agree that droplets, and not aerosols, are mostly responsible for the rapid rate at which the flu virus typically spreads. Though the flu virus can be airborne in certain environments, it typically is not. For it to spread via aerosols, the conditions — particularly those pertaining to temperature, humidity and crowd size — must be just right.

How the Flu Spreads Through Contact

The flu virus can survive for a surprisingly long time on hard surfaces or human skin. One study of the virus found that it could survive for up to two days on hard surfaces and up to 12 hours on soft textures, such as cloth and tissues. It makes sense, then, that one way in which the flu virus spreads is through contact.

When a surface comes into contact with viral droplets — which it often does through touch, sneezing, coughing and talking — that surface remains infected either until the virus dies or someone cleans it. If another person touches the infected surface and then touches his or her mouth, nose or eyes, the virus can easily enter the body. At this point, whether the person becomes sick is a matter of how strong his or her immune system is.

Though the flu spreading through contact is less common than it spreading via the air, it is important to understand that transmission can and does happen in this way.

How Long Is a Person Contagious With the Flu?

A sick person can spread the flu virus as early as one day before the onset of symptom and for up to five to seven days after the onset of symptoms. Most people recover within five to seven days, but if you do not, know that you are still contagious until your symptoms disappear.

Children and people with weak immune systems are often contagious for longer. This is because, as their bodies struggle to fight the virus, they can still shed it through droplets and contact.

When Is a Person Sick With the Flu Most Contagious?

Experts believe that people are most contagious around days three and four of having the flu virus. This is because it is around this time they cough and sneeze the most. The more droplets a person launches into the air, the more likely he or she is to infect others.

How Can You Tell You Are Contagious With the Flu?

The most definitive sign that you are still contagious with the flu virus is a fever. So long as you have a fever, the virus is alive and well inside your body. Your fever breaking is a sign that your immune system is weakening the virus, meaning your level of contagion is lower. However, for the health and courtesy of your family, friends and community, you should act like you are contagious until your symptoms recede entirely.

Do Flu Medications Help Stop the Spread?

There are several powerful flu medications on the market today, including Tamiflu, Rapivab, Relenza and Xofluza. Though these medications help reduce the severity of symptoms, if not prevent them entirely, they cannot make you un-contagious. They can, however, minimize the length of time you are sick, meaning they can minimize the length of time you can spread the virus.

How To Prevent the Flu

Understanding how the flu is spread can go a long way toward helping you take steps to prevent it. For instance, knowing that the flu can spread via airborne droplets and particles that come from coughing, sneezing or talking can encourage you to cough and sneeze into your elbow and to keep a safe distance from people with whom you need to communicate. Understanding that the virus can live for up to two days on hard surfaces may motivate you to sanitize surfaces after each use.

Some other tips you can use for reducing the spread of the flu virus are as follows:

  • Maintain a six-foot distance from people who are sick, and avoid any direct contact with infected persons
  • Avoid touching your nose, mouth or eyes, especially when out in public
  • Sanitize hard surfaces after each use
  • Wash your hands with soap and water frequently, especially when handling items that are not yours and yours alone
  • Use hand sanitizer when soap and water are not readily available

If you have the flu, do the following:

  • Stay home until your fever breaks
  • Cover your mouth and nose when sneezing and coughing
  • Wear a mask until you are certain you are no longer contagious
  • Limit your contact with people outside of your home as best that you can

The Bottom Line

The flu is a highly contagious and easily transmittable virus, evident in the alarming flu rates year after year. You can do your part to reduce the spread by taking precautions to keep yourself healthy or, if you do contract the virus, from spreading it to others.

 
 
 

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