Person to Person

The (CDC) Center for Disease Control has reported that a majority of people spread the flu every time they sneeze and disperse micro droplets within the surrounding air.  Estimates indicate that people within 6 feet of an infected individual may catch the virus.  The primary method of infection is the inclusion of micro droplets inhaled into the lungs.


It is far less likely that someone will catch the virus from touching a door knob.

To avoid catching or giving the flu to someone else this season:

  • Stay home if you feel the flu symptoms coming on
  • Wash you hand with soap and water.
  • Frequently touched surfaces should be cleaned often.



The Flu Is Contagious

Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. Children may pass the virus for longer than 7 days. Symptoms start 1 to 4 days after the virus enters the body. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Some persons can be infected with the flu virus but have no symptoms. During this time, those persons may still spread the virus to others.


More CDC Info. 

A better understanding of influenza transmission could help improve the infection control procedures and equipment used by health care workers. NIOSH has been conducting research for several years to learn more about the underlying science of influenza transmission, with a particular focus on airborne transmission and the protection of health care workers during a future pandemic. Here are some of the questions that are being addressed:


Is there a correlation between exposure to airborne influenza and illness among healthcare workers?

A combination of three approaches is being used to better understand worker exposure to influenza and its consequences. First, aerosol sampling will be conducted in a health care clinic. Second, the amount of genetic material (RNA) from influenza virus on surgical masks, respirators and gloves worn by health care workers and on the surfaces of equipment and furniture in the clinic will be measured. Third, the health status and any occurrences of influenza among the workers in the study will be monitored. This project is part of a large multi-hospital study to compare the relative effectiveness of surgical masks and respirators in preventing influenza among health care workers.


Can better methods be developed to detect infectious airborne influenza virus? 

The current methods for determining the infectivity of influenza aren’t sensitive enough to work with the small amounts of virus in a typical aerosol sample. NIOSH researchers are developing new, more sensitive methods of measuring influenza virus viability. One technique is a hybrid system called a “viral replication assay” that combines PCR with a more traditional culture method for increased sensitivity. A second technique uses genetically modified cells that glow faintly when they are infected with the influenza virus. This luminescence can be detected using standard laboratory equipment.


How well do different types of personal protective equipment perform under different exposure scenarios? 

To explore this, NIOSH researchers constructed a simulated medical examination room containing a custom-built coughing machine that can cough an influenza-laden aerosol into the room much like a patient would, and a breathing machine that can simulate a health care worker treating the patient. The breathing machine can be outfitted with personal protective equipment (PPE), such as surgical masks, respirators, face shields, and powered air-purifying respirators (PAPRs). The simulated exam room is now being used to study how well different types of PPE and combinations of PPE protect from large spray droplets and small aerosol particles at shorter and longer distances.


Researchers at NIOSH have presented their work at scientific and public health conferences, and several articles have been published in peer-reviewed scientific journals. Information on NIOSH influenza research and influenza-related Health Hazard Evaluations can be found at and In addition, the CDC provides a comprehensive set of guidelines for preventing transmission of influenza in healthcare settings at


Experts think influenza may be spread to uninfected people in three ways: large-particle respiratory droplet transmission, airborne transmission, and contact (or fomite) transmission. Most experts think that influenza viruses are spread mainly by large-particle respiratory droplets produced when people infected with influenza cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled.  Transmission via large-particle droplets requires close contact between source and recipient persons, because droplets do not remain suspended in the air and generally travel only a short distance (usually less than 2 meters) through the air. Airborne transmission (via small particles suspended in the air for extended periods of time) also is thought to be possible, although data are limited. Less often, a person might also become infected with influenza by touching a surface or object that has influenza virus on it and then touching his or her own mouth or nose.