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.

When the cell can no longer contain all those copies, it bursts. Now, there are hundreds of thousands of viruses attaching themselves to the other healthy cells in the body, exponentially increasing the infection process.

The virus incubates over a few days and the infected person starts feeling achy, fatigued and a little feverish as the bug makes itself at home throughout the body. Pretty soon that person won't be kissing much more than Kleenex.

Taking Back the Body

The body, however, has ways to fight back. "[The healing process] is a little like warfare," says Howard Berg, professor of molecular and cellular biology at Harvard University.

Your body, the fallen warrior, may be sneezing, running a fever and experiencing muscle aches, a drippy nose and a sore throat, but that's the good news. It shows your immune system is mobilizing for action, according to Northwestern's Smith.

Lymphocytes, colorless cells capable of spontaneous motion, are part of the army of cells responsible for that immune response. When stimulated by certain antigens, such as the flu virus, lymphocytes secrete chemicals that act on other cells, recruiting them to join the fight against the virus. When the troops have all been rallied, some of the lymphocytes evolve into killer T cells, which can actually ferret out and attack specific infected cells.

The result of all this action is inflammation in the lungs and a general malaise throughout the body, but ultimately in a healthy person the immune system wins, things calm down and health is restored.

The whole process from infection to incubation back to health generally takes about two weeks, and for healthy children and adults, is not considered life-threatening. For unhealthy or older people, however, the flu can be deadly.

Because each kiss varies in time and intensity, there is no way of knowing how much kissing sets you up for cellular attack, but experts estimate it takes only 10 viral particles to transfer an infection. So, the longer and more intensely two people make out, the more likely it is a virus can invade a partner.

"It's a time and quality phenomenon," says Smith.

According to the American Lung Association, there were more than 95 million estimated cases of influenza nationwide, resulting in 191.9 million bed days and an estimated 70.2 million work-loss days in 1996, the latest data available. The organization estimates the total annual costs of influenza in the United States are $14.6 billion.

Now, don't you feel better that you're all alone?