Historically, influenza (the flu) epidemics have cased havoc. Charlemagne’s army may have been decimated by the flu during an epidemic in 876. The great influenza pandemic of 1918-1919, the 20th century’s worst epidemic, killed millions of people. During World War I, the number of American killed by influenza (44,000) almost was equal to the number killed in battle (50,000). As the nation entered World War II, the military made influenza vaccination mandatory.

Influenza is a contagious disease spread by person-to-person contact and caused by the influenza virus. Peak flu season occurs usually from late December through March. There are three basic flu germs, variants of which are popularly designated according to where they first strike - that is, Hong Kong B, Bangkok A, and so forth. It is important to remember that influenza viruses are constantly changing, so an antibody made against one strain will become less effective against new strains as influenza strains evolve over time. In addition, different types of influenza viruses circulating and different variants within virus types, and the same type of flu virus does not necessarily circulate each year. For instance, during the 2005-2006 flu season, influenza A (H3N2) viruses predominated; however, infection with influenza A (H3N2) virus would not provide protection against influenza B or influenza A (H1N1) viruses. The viruses that cause flu are prone to mutation, making the manufacture of vaccines an annual guessing game of sorts. If a new mutation pops up anywhere in the world, resulting from a major change (antigenic “shift”), it will quickly spread, leaving most people unprotected.

A flu shot can help prevent one from getting sick, but even with the flu vaccine available, each year millions of people get sick, and some tens of thousands die from the flu.

When complicated by pneumonia, it is one of the 10 most common causes of death in the United States. Most people who get a flu shot have no serious problem from the vaccination. Those over age 60 should get a flu shot every year.

HEPATITIS
Hippocrates was the first to note epidemics of jaundice, a telltale characteristic of hepatitis. Hepatitis is a gastroenterological disease featuring inflammation of the liver. Most cases of acute hepatitis are due to viral infections. There are many types of hepatitis, and the disease can be contracted in a few different ways. Hepatitis A is transmitted by the orofecal route and is contracted through contaminated food or water. This form of hepatitis does not lead to chronic or lifelong disease, and just about everyone who gets hepatitis A has a full recovery. Hepatitis B can be contracted from blood, semen, and saliva (making it one of the venereal diseases) and also from tattoos. Hepatitis B can be a serious infection that can cause liver damage; some individuals are not able to get rid of the virus, which makes the infection chronic. Before routine testing of the blood supply, thousands of deaths occurred each year from post-transfusion hepatitis B. Fortunately, this is no longer a risk.

Hepatitis C is spread the same way as hepatitis B through an infected person’s blood and other body fluids as well as from injection drug use. Hepatitis C is a chronic infection and often causes liver damage. Hepatitis D can only thrive in cells also infected with hepatitis B and is not common. It can be spread through infected blood, dirty needles, and from unprotected sex with a person infected with hepatitis virus. Hepatitis E can be contracted from host to host via fecal-oral contact and contamination of water. This type of hepatitis does not occur often in the United States and does not cause long-term damage to the liver. In 1991, a recombinant hepatitis B vaccine was recommended for all newborn infants and children. There is no vaccine for hepatitis C, D, or E.

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Tony Rosen, MPH, MD
Tony Rosen, Division of Geriatric Medicine and Gerontology, Weill Cornell Medical College, Cornell University, New York, New York;

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REFERENCES

1. Barquest N, Domingo P. Smallpox: the triumph over the most terrible of the ministers of death. Ann Internal Med. 1997;127:627.
2. US Centers for Disease Control and Prevention. Ten great public health achievements in the twentieth century, 1900-1999.
3.   Parker AA. Implications of a 2005 measles outbreak in Indiana for sustained elimination of measles in the United States. New Engl J Med. 2006;355:1184.
4. Okonek BAM, Peters PM. Vaccines: how and why
5. Baxby D. Vaccination: Jenner’s Legacy. Berkeley, UK: Jenner Educational Trust; 1994. 6. Parish HJ. A History of Immunization. Edinburgh, UK: Livingstone; 1965.
6. Gross CP, Sepkowitz K. The myth of the medical breakthrough: smallpox, vaccination, and Jenner reconsidered. Int J Infect Dis. 1998;3:54-60.
7. Salmon DA,  et al.  Compulsory vaccination and conscientious or philosophical exemptions: past, present, and future. Lancet. 2006;367(9508):436-442.

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