AromatheraphyHistory of Influenza
Influenza A and B viruses continually undergo antigenic drift. This process accounts for most of the changes that occur in the viruses from one influenza season to another. influenza virus is difficult to control because it is not limited to human populations. Various strains of the virus can infect pigs, horses, and birds (including chickens). Antigenic shift occurs only occasionally. When it does occur, large numbers of people, and sometimes the entire population, have no antibody protection against the virus. This may result in a worldwide epidemic, called a pandemic.Influenza pandemics occur when antigens change slightly by antigenic drift. The history of influenza states that the pandemics occurred in 1918, 1957, and 1968, each of which resulted in large numbers of deaths. The reason that so many influenza epidemics seem to begin in Asia is the close contact between human and animal populations in rural China. When people work on or near farms with pigs and chickens, influenza viruses can spread between species, thereby leading to a new form of influenza that may cause an epidemic. The most disastrous pandemic recorded in history of influenza if from 1918-1919 during which more people died from influenza than the Great War. This was commonly known as "Spanish Flu" or "La Grippe". The history of influenza records that 20 million people died in just 120 days, with 12.5 million in India, half a million in the United States, and more than half the population of Alaska died. (Ingrahm, 538)
There are still many things about influenza viruses that are not understood. Although the newly emerged type A(H3N2) virus caused only moderate mortality in 1968 compared with other pandemic viruses, this virus has continued to cause substantial mortality as it has continued to circulate and evolve. In the years since its emergence, type A(H3N2) epidemics have caused more than 400,000 deaths in the United States alone, and more than 90% of these deaths have occurred among elderly people. Of the influenza viruses currently in worldwide circulation, A(H3N2) still has the most severe overall impact.
History of influenza suggests that influenza pandemics have happened during at least the last four centuries. During the 20th century, three pandemics and several "pandemic scares" occurred. These are described in more detail below.
- 1918: Spanish Flu
The Spanish influenza pandemic is the catastrophe against which all modern pandemics are measured. It is estimated that approximately 20 to 40 percent of the worldwide population became ill and that over 20 million people died. Many people died from this very quickly. - 1957: Asian Flu
In February 1957, the Asian influenza pandemic was first identified in the Far East. In preparation, vaccine production began in late May 1957, and health officials increased surveillance for flu outbreaks. Most influenza-and pneumonia-related deaths occurred between September 1957 and March 1958. The elderly had the highest rates of death. Although the Asian flu pandemic was not as devastating as the Spanish flu, about 69,800 people in the U.S. died. - 1968: Hong Kong Flu
In early 1968, the Hong Kong influenza pandemic was first detected in Hong Kong. The first cases in the U.S. were detected as early as September of that year, but illness did not become widespread in the U.S. until December. - 1976: Swine Flu Scare
When a novel virus was first identified at Fort Dix, it was labeled the "killer flu." Experts were extremely concerned because the virus was thought to be related to the Spanish flu virus of 1918. - 1977: Russian Flu Scare
In May 1977, influenza A/H1N1 viruses isolated in northern China, spread rapidly, and caused epidemic disease in children and young adults worldwide. The 1977 virus was similar to other A/H1N1 viruses that had circulated prior to 1957. - 1997: Avian Flu Scare
The most recent pandemic "scares" occurred in 1997 and 1999. In 1997, at least a few hundred people became infected with the avian A/H5N1 flu virus in Hong Kong and 18 people were hospitalized. In 1999, another novel avian flu virus – A/H9N2 – was found that caused illnesses in two children in Hong Kong. Although both of these viruses have not gone on to start pandemics, their continued presence in birds, their ability to infect humans, and the ability of influenza viruses to change and become more transmissible among people is an ongoing concern.