What is the difference between a cold and the flu? What over-the-counter medicine is the one to get when you feel like you have a cold coming on? I did get the flu shot this year as I do every year.
It is clear that the viruses causing the flu and those causing colds are different, so why is there so much confusion about distinguishing between a cold and the flu when someone is sick? The answer to this is that all of the viruses can cause overlapping syndromes — that is, the symptoms may be similar enough so that neither the person with the disease nor their doctor can tell them apart. Until recently there have been no rapid tests to distinguish the two. Also until recently, there has been no treatment to kill the viruses, so it was not critical for doctors to be able to tell them apart.
About six different virus families cause the disease that we call a cold. The most common of these are rhinoviruses, the coronaviruses and the adenoviruses. Some, like the adenoviruses, are more likely to cause symptoms in the nose, throat and chest, and fever, whereas the coronaviruses are more likely to cause only nose and throat symptoms with no fever. There are two flu viruses, and they usually cause abrupt onset of fever, sore throat, headache and muscle aches. Some of the cold viruses may come on this way as well, so without a specific test, it is impossible to distinguish them.
Historically, doctors have diagnosed flu when it was present as an epidemic, and it was safe to say that anyone with the typical symptoms had it. Flu has always tended to sweep through countries as an epidemic, in the southern hemisphere during their winter, and the northern hemisphere during ours. The influenza A virus is responsible for most of these epidemics. It tends to mutate frequently, so that the form of the virus seen in succeeding years is slightly different. This is referred to as antigenic drift, and accounts for the fact that having the flu one year (or the flu vaccine), does not protect you the next year, and so on. Every 20-30 years, a major mutation occurs, referred to as an antigenic shift, and those years the epidemic tends to be much worse because the immunity that people accumulated in previous years offers even less protection than usual.
There are still no vaccines available against any of the viruses causing colds. There are, of course, vaccines against the major strains of flu viruses, and they are highly effective. Like today’s letter writer, I always get the flu vaccine, and have not had a case for years. This would not protect me, of course, against any of the cold viruses. I often see people who come in disgusted because they got the flu shot, but still got very sick, and assume that the vaccine did not work for them. They have come down with one of the cold viruses, and since the syndromes overlap so much, we can’t tell them apart.
Standard antibiotics do not help either the flu viruses or those that cause colds. In recent years, a number of special antibiotics effective against the flu viruses have been developed. The most recent ones are effective against both influenza A and influenza B. Oseltamivir (Tamvir) is a capsule taken twice daily. Zanamivir is an inhaled powder which uses a special inhaler, and is also taken twice daily. There is little evidence to indicate that one is better than the other. Both must be started within two days of the beginning of symptoms or they won’t work, and both reduce the length of the illnes by one to two days. Neither is effective against any of the cold viruses, and it is therefore recommended that they be prescribed only if a known flu epidemic is occurring in the community.
Over-the-counter medicines may help some of the symptoms of both colds and flu. For adults, I suggest a cough medicine containing dextromethorphan. For the runny, stuffy nose, an antihistamine like diphenhydramine together with a decongestant like pseudoephedrine may help. The diphenhydramine makes people sleepy and the pseudoephedrine make them jittery. For fever and pains, I like plain old aspirin, unless someone is allergic or their stomachs can’t take it, in which case acetominophen is a poor second choice. Children should not be given aspirin. There are lots of brand names on the shelves of every pharmacy containing various combinations of these ingredients. Always buy the generic or house brands, and always the cheapest. They work just as well as the expensive brands.