Diseases and vaccines

Influenza

PATH is advancing new technologies to develop safe, effective, and affordable vaccines against influenza. PATH will collaborate with a number of public- and private-sector partners to advance the development of promising new vaccines that could be produced more quickly and used in developing countries during an influenza pandemic. Learn more about PATH’s work against pandemic influenza.

Influenza disease

  • Influenza, or flu, can be caused by three different virus types: influenza A, influenza B, and influenza C.
  • Influenza occurs in seasonal patterns worldwide and is estimated to cause 3 to 5 million cases and 300,000 to 500,000 deaths each year. The most severe influenza pandemic, in 1918, infected up to 50 percent of the world’s population and caused 20 to 50 million deaths worldwide.
  • Influenza symptoms include fever, headache, cough, tiredness, sore throat, runny or stuffy nose, body aches, and diarrhea or vomiting. These symptoms are common to several illnesses, including the common cold, which makes it harder to determine the incidence of influenza, particularly in countries where a doctor is not readily accessible.
  • The most common method of influenza transmission is human-to-human, although animal-to-human transmission is possible, particularly pig-to-human. A person may infect others even though they seemingly have no influenza symptoms. Currently, the avian influenza strain H5N1 is not spread from human-to-human; however, there is growing concern that the strain could evolve resulting in human-to-human transmission.
  • Influenza can be treated with antiviral drugs, which can lessen the severity of disease and are effective against influenza virus types A and B.

Influenza vaccines

  • Each year, currently circulating influenza strains are tested to determine the three strains that will be included in the vaccine, most commonly made from embryonated chicken eggs. Usually, one to two strains covered by the vaccine change each year.
  • The flu shot (using inactivated flu virus) is approved for use among healthy people six months of age or older and those with chronic medical conditions (such as asthma, diabetes, or heart disease). The intranasal, attenuated, live-virus vaccine, FluMist®, is recommended for healthy individuals between 2 and 49 years old who are not pregnant.
  • With the emergence of the H5N1 avian influenza strain, new vaccine development efforts are underway to prepare for a possible influenza pandemic. These new efforts focus on technologies that can be produced more easily and affordably than current vaccines and do not rely upon egg-based technology, which could be compromised in the event of an avian-strain pandemic.

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