By the late 1890s and early 1900s, scientists understood that microorganisms caused disease. Most disease research focused on bacteria, which are large enough to be visible under a light microscope and can be isolated using filters. But technology at the time prevented scientists from identifying a disease-causing agent as small as a virus.
In the 1890s German bacteriologist Richard F. J. Pfeiffer reported that he had identified the bacterium Haemophilus influenzae as the cause of influenza. Further investigation indicated, however, that this bacterium was not always present in people with influenza. Scientists concluded that the Haemophilus influenzae bacterium probably played a role in secondary infections.
Meanwhile, the long-held belief that influenza only occurred in humans was overturned. Around 1930 American bacteriologist Richard E. Shope showed that it was possible to transfer an influenza-like disease from one pig to another. Thereafter scientists chiefly used animals in their research on influenza.
In 1933 English physicians Wilson Smith, Christopher H. Andrewes, and Patrick P. Laidlaw removed secretions from the throat of a human flu victim, filtered out a suspect infectious agent, and injected the material into ferrets. The ferrets then developed influenza, thereby demonstrating that the infectious agent caused influenza. Research performed by other researchers eventually proved that the infectious agent was the influenza A virus. The influenza B virus was isolated in 1940, and the influenza C virus in 1950.
In 1941 scientists demonstrated that a vaccine could control influenza. The first vaccine was developed to protect soldiers during World War II (1939-1945). Early influenza vaccines produced from the 1940s to the mid-1960s were all made from killed viruses, which cannot cause infection. But these early vaccines contained impurities that produced fever, headaches, and other severe side effects. Improved pharmaceutical procedures have made today’s vaccines almost free from impurities, greatly reducing the chance that the vaccines will cause side effects.
Despite these improvements, developing influenza vaccines remains a challenge. Current vaccines do not provide 100 percent protection against influenza, and they can be quickly rendered ineffective by changes in the viruses themselves. Some scientists, believing that vaccines will never be able to completely control influenza, work to expand the number and variety of drugs available to treat the disease once symptoms appear. Until a cure for influenza is discovered, public health officials hope that identifying and reporting new viral strains quickly will result in timely actions that prevent the recurrence of deadly pandemics. Even in best-case scenarios, however, influenza is expected to remain a formidable opponent of human health.
In the 1890s German bacteriologist Richard F. J. Pfeiffer reported that he had identified the bacterium Haemophilus influenzae as the cause of influenza. Further investigation indicated, however, that this bacterium was not always present in people with influenza. Scientists concluded that the Haemophilus influenzae bacterium probably played a role in secondary infections.
Meanwhile, the long-held belief that influenza only occurred in humans was overturned. Around 1930 American bacteriologist Richard E. Shope showed that it was possible to transfer an influenza-like disease from one pig to another. Thereafter scientists chiefly used animals in their research on influenza.
In 1933 English physicians Wilson Smith, Christopher H. Andrewes, and Patrick P. Laidlaw removed secretions from the throat of a human flu victim, filtered out a suspect infectious agent, and injected the material into ferrets. The ferrets then developed influenza, thereby demonstrating that the infectious agent caused influenza. Research performed by other researchers eventually proved that the infectious agent was the influenza A virus. The influenza B virus was isolated in 1940, and the influenza C virus in 1950.
In 1941 scientists demonstrated that a vaccine could control influenza. The first vaccine was developed to protect soldiers during World War II (1939-1945). Early influenza vaccines produced from the 1940s to the mid-1960s were all made from killed viruses, which cannot cause infection. But these early vaccines contained impurities that produced fever, headaches, and other severe side effects. Improved pharmaceutical procedures have made today’s vaccines almost free from impurities, greatly reducing the chance that the vaccines will cause side effects.
Despite these improvements, developing influenza vaccines remains a challenge. Current vaccines do not provide 100 percent protection against influenza, and they can be quickly rendered ineffective by changes in the viruses themselves. Some scientists, believing that vaccines will never be able to completely control influenza, work to expand the number and variety of drugs available to treat the disease once symptoms appear. Until a cure for influenza is discovered, public health officials hope that identifying and reporting new viral strains quickly will result in timely actions that prevent the recurrence of deadly pandemics. Even in best-case scenarios, however, influenza is expected to remain a formidable opponent of human health.
