Colds & Flu Support Group

Acute nasopharyngitis, often known as the common cold, is a mild viral infectious disease of the upper respiratory system (nose and throat). Symptoms include sneezing, sniffling, nasal congestion; scratchy, sore, or phlegmy throat; coughing; headache; and tiredness. Colds typically last three to five days, with residual coughing lasting up to three weeks. As its name suggests, it is the most common of all human diseases, infecting subjects at an average rate of slightly over one infection per year per person. Infection rates greater than three infections per year per person are not uncommon in some populations. Children and their caretakers are at a higher risk, probably due to the high population density of schools and the fact that transmission to family members is highly efficient.

Influenza, commonly known as the flu, is an infectious disease that infects birds and mammals (primarily of the upper airways and lungs in mammals) and is caused by an RNA virus of the Orthomyxoviridae family (the influenza viruses). The most common and characteristic symptoms of influenza in humans are fever, sore throat, myalgia (muscle pains), severe headache, cough, and malaise (weakness and fatigue).

Influenza, commonly known as the 'flu, is an infectious disease that infects birds and mammals (primarily of the upper airways and lungs in mammals) and is caused by an RNA virus of the Orthomyxoviridae family (the influenza viruses). The most common and characteristic symptoms of influenza in humans are fever, pharyngitis (sore throat), myalgia (muscle pains), severe headache, coughing, and malaise (weakness and fatigue).

A cold and a 'stomach flu' are very different from a flu. Influenza can be far more severe than the common cold and can even lead to death. Influenza and the common cold are caused by very different viruses. Gastroenteritis is commonly called "stomach flu" or "24 hour flu"; but that is a misnomer as it is not connected with actual flu.

Flu rapidly spreads around the world in seasonal epidemics, killing millions of people in pandemic years and hundreds of thousands in nonpandemic years. It creates health care costs and lost productivity. Three influenza pandemics in the 20th century, each following a major genetic change in the virus, killed millions of people all over the world. The world's current major influenza pandemic threat is H5N1; but it is at present mostly a flu in birds, not in people.

Influenza reaches peak prevalence in winter, and because the Northern and Southern Hemisphere have winter at different times of the year, there are actually two flu seasons each year. Therefore, the World Health Organization (assisted by the National Influenza Centers) makes two vaccine formulations every year; one for the Northern, and one for the Southern Hemisphere.

While most influenza outbreaks in the Northern Hemisphere tend to peak in January or February, not all do. For example, the influenza pandemic of 1918 and 1919 reached peak virulence during late spring and summer worldwide, and not until October in the US. It remains unclear why outbreaks of the flu occur seasonally rather than uniformly throughout the year.

One possible explanation is that, because people are indoors more often during the winter, they are in close contact more often, and this promotes transmission from person to person. Another is that cold temperatures lead to drier air, which may dehydrate mucus, preventing the body from effectively expelling virus particles. The virus may also linger longer on exposed surfaces (doorknobs, countertops, etc.) in colder temperatures. Increased travel and visitation due to the holiday season may also play a role.

It is possible and in many cases recommended to get vaccinated against influenza with a flu vaccine. Its effectiveness varies with many criteria.

Due to the high mutability of the virus, a particular flu vaccine formulation usually only works for about a year. The World Health Organization co-ordinates the contents of the vaccine each year to contain the most likely strains of the virus that probably will attack the next year.

It is possible to get vaccinated for the season and still catch the flu. The vaccine is reformulated each season for a few specific flu strains, but cannot possibly include all the different strains actively infecting people in the world for that season. This means that you could catch a virus not covered by the vaccine. Also, it takes about six months for the manufacturers to formulate and make the millions of doses required to deal with the seasonal epidemics; occasionally a new or overlooked strain becomes prominent during that six months and infects people even though they've been vaccinated (as in the 2003-2004 season). The vaccine may have partial coverage for these unexpected strains. It is also possible to get infected and then get vaccinated the next day, before flu symptoms appear, and still get sick with the very strain that the vaccine is supposed to prevent. The vaccine can take a few days to become effective.

Vaccines can cause the immune system to react as if the body were actually being infected, and general infection symptoms (many cold and flu symptoms are just general infection symptoms) can appear, though these symptoms are usually not as severe or as long lasting as the flu.