Influenza Jack Edwards,
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INTRODUCTION The word "flu" today encompasses such a large variety of vague ailments and symptom-complexes that it would be impossible to discuss them aJI in this paper. Respiratory flu often refers to the common cold, and when a person says he has had stomach flu , it usually means he has spent a miserable night running to the toilet. In this paper, I shall attempt to describe influenza in its pure form. Before 1890, influenza was practicaJiy unknown, and except for a minor outbreak in 1855, was not a significant cause of death. In fact, it was becoming an almost extinct disease in Britain. .According to Burnet and Clark, influenza remained endemic somewhere in Central .Asia until the spring of 1889, when its virulence became exalted in Bukhara. Other parts of Russia were affected in the fall , and by December the epidemic had spread to Western Europe. The 1889-90 pandemic affected a large part of the world but was not associated with particularly high mortality for young adults. The first wave in January 1890 was succeeded by others in May 1891 and January 1892, causing progressively high mortality. Influenza has never since fallen to the pre 1889 low level and has become an important cause of mortality and morbidity in most temperate climates. In 1918-19, influenza accounted for the most lethal pandemic known in history. .According to Frost, there had been a steady increase in the mortality from influenza and pneumonia in New York betwee.n 1914 and 1918. It is questionable whether this progressive rise can be ascribed to the activity of influenza .A, or of any other single virus. In fact it is not known what led to the catastrophic events of 1918-19. In the early months of 1918 the influenza had no unusual properties, but in June in Britain, there was some indication that it was beginning to kill young adults. The really virulent form of the disease appeared at about the same time in the U.S.A. around Boston, and in Brest France - ports of embarkation and debarkation of .American troops corning to Europe. The rapid spread of the lethal kind of influenza all over the world is a familiar story. It is estimated that at least 15 million people died as a result. Mter the pandemic years, influenza gradually returned to its habits of killing the old and weak, rather than the young and vigorous. This reversion took at least three years in the U.S.A. and perhaps a decade in Britain. We may suppose that the 1918-19 influenza lacked some property enabling it to persist between epidemics, so that a less spectacu lar derivative gradually replaced it. Since the great pandemic the mortality from influe.nza has been falling and the peaks have been tending to be smaJier and more widely spaced. However, influenza is still an important cause of morbidity and lost working time as witnessed in London this winter.
DEFINITION AND ETIOLOGY Influenza is an acute, suddenly onsetting, infectious disease of viral etiology, usually occurring in epidemic form and characterized by general symptoms of fever, chills, headache, myalgia, and by mild upper respiratory symptoms. In 1892 Pfeiffer described a small gram negative bacillus, which grew with difficulty upon blood media, as the causative agent of influenza. It is known as Pfeiffer's bacillus or Hemophilus influ-
enza and bas since been proved to be only a common secondary invader of influenza. In 1933 the true etiology was established in England by Smith, Andrews, and Laidlaw, with the isolation of a vi rus from gargling of patients, during a typical epidemic of influenza. It was designated influenza A virus. In 1940 a second etiological type of the virus was isolated independently by Francis and Magill, known as influenza B VICUS.
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