Cold and Flu Season Arrives

September 21, 2004
Contact: News Office (415) 502-6397

By Dr. Homer Boushey and Theresa Ward

September does not just bring the end of summer and return to school, it also marks the beginning of the "cold and flu" season that runs until April. Throughout the northern hemisphere, the cold and flu season starts with rhinovirus infections, so named because they commonly affect the nose. Influenza, parainfluenza, respiratory syncytial virus and other viruses peak later.

Rhinoviruses are the most common cause of the common cold and are the most common infection in humans, UCSF experts say. While most people can expect to get one or two colds every year, small children have many more -- up to as many as 12. And these infections are easily spread -- explaining why epidemics of "colds" occur in the fall, after children return to school. It also explains why the population most affected after children are people in their early 30s - the parents of school-aged children. There are more than 100 different types of rhinovirus. So even though infection with any one type of rhinovirus results in partial immunity against that type, more are lurking so we'll keep getting colds.

So here we are at the start of the rhinovirus season. What can be done about it? There is no treatment for common colds, although several possible treatments are under development. So the approach is twofold. One is simple symptomatic therapy: taking aspirin or Tylenol, decongestants and getting plenty of fluid and rest. For the great majority, the illness runs its course over five to seven days. The other approach is preventive. Cold viruses are spread by two routes: by hand contact and by aerosol. Spread by hand contact can be reduced by frequent hand washing and has been shown to decrease transmission of colds in schools. Aerosol transmission is harder to prevent. When sneezing or coughing, it's important to cover up, but that's not fool-proof protection for others nearby.

Link to Serious Conditions

For most people, the illness caused by rhinovirus infection is no more than a few days of a sore throat, runny nose and nasal congestion, so rhinoviruses weren't regarded as very important. But use of a new, sensitive, molecular technique -- the polymerase chain reaction -- for detecting different viruses has shown that cold viruses, especially rhinoviruses, are found in the nasal secretions or sputum of most patients with acute ear infections, acute bronchitis or acute sinusitis.

Rhinoviruses also are found in more than half of patients with asthma attacks, and also in patients with exacerbations of chronic obstructive pulmonary disease or cystic fibrosis. This means that the most common cause of the common cold can cause severe disease, especially in people with a pre-existing lung disease, even mild asthma.

Some studies also have shown that people taking treatments to suppress their immune system, like those with organ transplants, may develop severe illness, even pneumonia, from infection with ordinary cold viruses. This is why hospital wards for patients being treated for cancer or for organ transplant typically insist that health care providers not work on the ward when they have symptoms of a cold. It is also why they so often restrict visitors to adults. It is not that hospitals don't appreciate the importance to patients of seeing children and grandchildren, it is that children very commonly carry respiratory viruses.

Age may be another predisposing condition to bad effects of common colds. Rhinovirus colds - "the most common kinds of colds" - cause fever, loss of appetite and general malaise in elderly people. Rhinoviruses are so much more common than influenza that some experts calculate that these "cold viruses" account for more sick days in bed among the elderly than influenza itself.

Research on Asthma

For some people, the stakes are higher than just avoiding a cold. In fact, 5 percent to 7 percent of the U.S. population has asthma, and cold viruses are the most common cause of attacks of asthma. But that is not the whole story, for it is clear that asthma does not get worse every time a person with asthma catches a cold. This raises the question being studied by pulmonologist Homer Boushey, allergist Pedro Avila and registered nurse Theresa Ward at the Asthma Clinical Research Center at UCSF Medical Center: Why do some rhinovirus infections make asthma worse and others don't?

Some of the center's research focuses on differences in the asthmatic person's condition when catching a cold. For example, one study has found evidence that catching a cold during a period of exposure to an allergen, like grass pollen or cat dander, is more likely to cause an asthma attack. But the UCSF center's study found the opposite -- that exposing allergic people to an allergen made them more resistant to infection by a cold virus.

Researchers at the center are now focusing not on possible differences in the asthmatics infected, but in the viruses causing the infection. Their theory is that some rhinoviruses are more likely to make asthma worse than others. For the first time, this possibility can be examined using a new method for identifying viruses and determining their genetic sequence (through the ViroChip microarray) developed by Joe DeRisi's lab in the Biochemistry and Biophysics Department at UCSF. This new method offers a way to find out quickly not only that a rhinovirus is present, but also exactly which of the more than 100 types of rhinovirus it is. If some rhinoviruses are worse for asthma than others, then it may be possible to find out which part of the genetic code is responsible, and this could lead to developing new treatments or vaccines to prevent attacks caused by colds.

How to Help

What the center needs are some of the viruses that make asthma worse. If you have asthma and get a cold that makes your asthma worse, you may be infected with an "asthmagenic" rhinovirus. The UCSF Asthma Clinical Research Center would like to "capture" it. In brief, if you have asthma, the center would like to see you within a few days after your cold symptoms first appear, even if your symptoms are mild. It doesn't matter if the cold has not made your asthma worse. In fact, they would like to "capture" cold viruses that just cause colds, so that they can compare them to those that also make asthma worse.

If you are between 12 to 50 years of age, have asthma and want to learn more about helping UCSF's Asthma Clinical Research Center capture the viruses that cause any cold you catch, please call (415) 476-3492, especially if colds make your asthma worse. Or visit their Web site, and click on the "Short Cold Study."