Kissing Can Be Dangerous

— -- So, Cupid has flown the coop and love is not in the air. Settle in and get ready to feel smug. A smooch-free Valentine's Day may have advantages for your health.

By not kissing that special someone, you're also not exposing yourself to the 500 or so bacteria in your partner's mouth, and you're not letting viruses in either.

"Kissing is a great way to pass a virus," explains Dr. Lewis Smith, a professor of medicine at Northwestern University in Chicago. When an infected person exchanges fluids, or even touches, his or her partner, they basically set up their true love for total viral attack.

As your coupled friends, relatives and neighbors take pity on you spending your Valentine's Day all by your lonesome, you can have the last laugh: Here is an explanation of how the flu virus wreaks its havoc, even after the tenderest kiss.

The sparks may be flying between lovers, but on a cellular level, bugs are engaged in battle.

Attaches, Invades, Enters

Influenza A, a common strain of the flu virus, is clever. Its raison d'etre is to make copies of itself in a warm, nurturing environment, such as a human being. It gets to its target through droplets of fluid released in the air by an infected person's sneeze or cough. Or through the exchange of saliva otherwise known as a kiss.

Specially equipped with sticky proteins that allow it to attach to a person's healthy cells, the virus hangs on to the cell's surface until it can get in and co-opt the cell's machinery for its own purposes.

The viral particle is covered with something called a "glycoprotein envelope." The envelope is covered with two different kinds of enzymes — hemagglutinin, which is sticky and helps the virus to attach the healthy cells in the nose, throat or lungs, and neuraminidase, which helps the virus spread from cell to cell.

These two enzymes enable the virus to invade the cell. Once it penetrates the cell membrane, the virus redirects the cell's energy so that it unwittingly concentrates on creating copies of the unwelcome guest. The viruses then multiply and multiply.