Every time we touch the nose or mouth, bacteria and virus transfer between our hands and our face. This "self-inoculation" or transfer of germs from one body part to another, is a primary way by which end up spreading germs from contaminated surfaces to the faces of people and sick people to places surfaces crowded.

"There are many opportunities for washing and hand washing that recontamination" says Dr. Wladimir Alonso, global health researcher at the National Institute of Health in Bethesda.
The Dr.Alonso and colleagues randomized 249 people in public places in Washington, DC and in the Brazilian city of Florianopolis. The researchers studied the frequency with which these individuals played any common surface and then the mouth or nose. They found that people in the study were touching face an average of 3.6 times per hour and common objects an average of 3.3 times per hour.

This rate touching your nose or mouth indicates that people infected their hands as often as you wash.

"It is important to understand the basic mechanisms by which diseases are transmitted to make the most of the hand washing," said Dr. Alonso.

"If there is a virus in the respiratory deadly environment, this is something to bear in mind," Alonso said, pointing to the 2009 influenza pandemic, as an example of a situation where knowledge of self-inoculation may limit the spread of the disease.

Alonso said that knowing the frequency of self-inoculation should not turn people into hypochondriac, or lead to an uncomfortable or life in a constant state of alert. The immune system provides good protection against disease.

"But it is important to note that self-inoculation can occur very quickly after washing your hands," he said.

This study was published Nov. 15 in the journal Clinical Infectious Diseases.

Picture By James Gathany (CDC Public Health Image library ID 11162) [Public domain], via Wikimedia Commons