How Does the Flu Spread So Quickly?

Flu particles may be in the air up to six feet away from someone who is sick

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) During flu season, the flu often seems to spread like wildfire. Recent research gives some insight about how the flu spreads so quickly.

In the study, virus particles were found in the air up to six feet away from people suffering from the flu. People with more severe symptoms had more flu virus in the air around them. A total of 19 percent of people in the study had very high levels of flu in the air around them.

The authors suggested that caretakers and healthcare workers are at higher risk of catching the flu during normal daily activities. Taking extra caution around people with severe symptoms may be needed.

"Ask a doctor how to protect against the flu."

The study, led by Werner E. Bischoff, MD, PhD, of the Section on Infectious Diseases in the Department of Internal Medicine at Wake Forest School of Medicine in North Carolina, looked at patients who came to the hospital with flu-like symptoms during the 2010 to 2011 flu season.

The researchers tested 94 patients in all. They asked patients about their symptoms, medical history and any treatments they were using.

Each patient was tested for the flu using a mouth swab. Then, the researchers took air samples at one foot, three feet and six feet away from the patient’s head.

A total of 61 people (65 percent) tested positive for flu.

Of people who had the flu, 26 people (43 percent) had flu particles in the air around them. Five patients (19 percent) were considered to be high emitters because they had up to 32 times more flu virus in the air around them than others with the flu.

At all distances, there was enough flu virus in the air to be able to infect another person. The highest concentration of flu virus was within three feet of the patient’s head.

The researchers also found that the amount of virus in the air was higher at all distances when coughing and sneezing occurred.

People with more severe symptoms and who reported more disruption with daily life function had more flu virus in the air around them.

The authors concluded that healthcare workers and other caretakers may be at higher risk than previously thought.

The authors suggested using simple tests of symptom severity and daily life disruption to help to identify patients who are most contagious.

There were some limitations to the study. First, the study looked only at the amount of virus in the air. It did not measure whether or not other people were infected by the particles in air. Also, the study was conducted in a hospital setting, so the air around the patients was not controlled. The authors noted that there could have been some residual flu particles from other patients in the area.

This study was published January 30 in The Journal of Infectious Diseases. The study was funded by the Centers for Disease Control and Prevention. The authors report no conflicts of interest.

Reviewed by: 
Review Date: 
February 12, 2013
Last Updated:
February 13, 2013