Epidemics of the Past
Influenza: A Twentieth-Century Epidemic
On June 28, 1914, Archduke Franz Ferdinand, heir to the throne of the Austro-Hungarian Empire, was assassinated in Sarajevo, starting World War I. Four years and three months later, on November 11, 1918, an armistice was signed in Northern France ending “The Great War.” The death toll was enormous, estimated at 8 to 10 million, but it paled in comparison to the influenza pandemic that also struck in 1918. War, for all its horror and casualties, was actually less deadly than the outbreak of influenza.
In the spring of 1918, soldiers in the trenches in France complained of sore throats, headaches, and general malaise. Most of them recovered quickly, and only a few died. The soldiers called their illness the Spanish Flu although its origins were, and still are, unknown. By summer of that same year, soldiers' symptoms became much worse. One in five who got sick developed pneumonia or blood poisoning. Many died. Others developed a strange condition called heliotrope cyanosis—they literally turned blue! Almost all of them died within a few days. This second wave of the epidemic spread quickly. More than 70,000 American troops on the Western Front were hospitalized, and one-third of them died.
Influenza is a common, contagious respiratory infection caused by a virus with outbreaks of different forms occurring almost every winter with varying severity. It is characterized by fever, muscle aches, headache, and sore throat.
The virus did not play favorites in the war, and by the end of the summer, the infection had reached Germany, and over 400,000 civilians died there. The first cases in Britain showed up in Glasgow during May 1918, and in a few months' time the virus killed 228,000 Brits. The epidemic swept through the United States in September, and by early December about 20 million people were infected and 450,000 Americans had died. That was not the worst of it. India suffered the largest toll. The first cases appeared in Bombay in June 1918, followed by cases in Karachi and Madras. Many of India's doctors were serving with the British army, so the country was unprepared to deal with the enormity of their problem. In one year, 16 million people in India died.
The 1918-1919 worldwide epidemic, or pandemic, is estimated to have infected 500 million people resulting in nearly 40 million deaths.
The Flu Today
Today, the influenza virus appears virtually every year in a slightly different form and causes respiratory infections. Some years, cases are sporadic and local. In other years there are epidemics that can spread through cities, rural areas, and even whole countries.
Acute infections usually have a rapid onset and require medical attention to cure. Chronic infections may start slowly and last for a long time. Often medical help manages a chronic infection but cannot cure it.
Each winter, the flu is the most frequent cause of acute respiratory illness requiring medical care. It is highly contagious, affects all age groups, and has caused epidemics and pandemics of human disease for many centuries. During most flu seasons, up to 20 percent of the population becomes infected, and approximately 1 percent of those infected have to be hospitalized. Close to 20,000 Americans die from complications of the flu each year. In the United States, the flu pandemics of 1957 and 1968 were associated with an attack rate of up to 50 percent and an estimated 100,000 deaths.
Signs and Symptoms of the Flu
The flu virus spreads through the air. It moves from person to person primarily when someone who is infected coughs or sneezes. The incubation period is one to four days, and you can be infectious, or pass the virus to someone else, starting the day before symptoms begin, and lasting through five days after you get sick. The infectious period for children can be longer. Uncomplicated flu in adults and children is characterized by the abrupt onset of the following symptoms:
A major new strain of influenza appears approximately every 10 to 15 years, causing a worldwide flu epidemic.
Fever usually peaks within the first day and lasts up to five days.
The flu usually goes away after several days, although some symptoms, like coughing, can last for more than two weeks. In some people, the flu aggravates underlying medical conditions. The risks for complications, hospitalizations, and deaths from flu are higher among people over age 65, very young children, and people with underlying health conditions. During flu epidemics, deaths can result from pneumonia as well as from heart conditions and other chronic diseases.
A Quick-Change Artist
All viruses have genetic material, either DNA or RNA. Viruses replicate—make copies of themselves by using the machinery of their hosts to copy their DNA or RNA—in order to cause infection. During replication, errors in the sequence of the building blocks that make up DNA and RNA can occur, causing the resulting copies of the virus to be slightly different than their “parents.” If this happens a number of times, the virus changes enough to elude the antibodies that worked to kill it before.
As the flu virus grows and spreads, the replication of individual cells occurs many times, and the errors compound. Eventually, though the virus remains a flu virus, the cumulative effect of many genetic errors results in a new strain. This is similar to taking a word and rearranging the letters one by one. At first it might be nonsense, but eventually you could have a new word.
The United States will produce about 88 million doses of vaccine in 2002. Not all will be taken. In persons over age 65, the vaccination rate is about 65 percent. The vaccination rate for those age 18 to 64 is 31 percent.
If your body becomes infected with this new strain, it's as though it is meeting the virus for the very first time. The fact that you may have had the flu last year makes absolutely no difference. The antibodies your immune system produced in the past give you little or no protection against another flu virus type or subtype. This is why it is not possible to give a vaccine that gives us long-term immunity to the flu. It is also the reason for seasonal epidemics, and for the incorporation of one or more new strains into each year's flu vaccine.
Controlling the Flu
Each year the flu vaccine in the United States contains three strains representing the flu viruses most likely to circulate in the United States in the upcoming winter. The effectiveness of the vaccine depends on the age and health of the vaccine recipient and the degree of similarity between the viruses in the vaccine and those in circulation. When the vaccine and circulating viruses are similar, the vaccine prevents illness in approximately 70 to 90 percent of healthy people under 65. Among the elderly who live in nursing homes, the flu vaccine is most effective in preventing severe illness, secondary complications, and death.
Vaccinating people at high risk for complications before the flu season each year is the most effective means of reducing the flu's impact. When vaccine and epidemic strains are well matched, vaccination of health-care workers and others in close contact with people in groups at high risk—or among people living in closed settings like nursing homes or other chronic-care facilities—can reduce transmission and subsequent complications.
In Russia there is a flu vaccine that is given through the nose instead of by injection; this vaccine is under development in the United States. It is possible that the use of a vaccine without an injection may encourage more people to get flu shots each fall.
In view of its enormous human and economic toll, the flu remains a major target for improved vaccines, vaccine delivery, and antiviral treatment. The use of flu-specific antiviral drugs for treatment is an important adjunct to vaccine. However, these agents are not a substitute for vaccination.
Smallpox, plague, and influenza are just three examples of epidemics that have struck throughout history. They and other infectious diseases have caused devastation and death all around the globe. Although smallpox has been eradicated, there is still fear about its use as a bioterrorist weapon, and most other infectious diseases are still causing illness despite the implementation of better diagnosis, treatment, and prevention.