Influenza Epidemic »
Hong Kong Flu
Hong Kong Flu was a pandemic outbreak
of influenza A (H3N2) which occurred in 1968-69. This virus was
first detected in Hong Kong in early 1968 and spread to the United States
later that year where it caused about 34,000 deaths, making it the mildest
pandemic in the 20th century.
There could be several reasons why fewer people in the US died due to
this virus. First, the Hong Kong flu virus was similar in some ways
to the Asian flu virus that circulated between 1957 and 1968. Earlier
infections by the Asian flu virus might have provided some immunity
against the Hong Kong flu virus that may have helped to reduce the severity
of illness during the Hong Kong pandemic.
Second, instead of peaking in September or October, like pandemic influenza
had in the previous two pandemics, this pandemic did not gain momentum
until near the school holidays in December. Since children were at home
and did not infect one another at school, the rate of influenza illness
among schoolchildren and their families declined.
Because of its similarity to the 1957 Asian Flu (which was the H2N2
strain, differing from the Hong Kong flu only in the chemical arrangement
of the hemagglutinin protein as a result of antigenic shift) and possibly
the subsequent accumulation of related antibodies in the affected population,
the Hong Kong flu resulted in much fewer casualties than most pandemics.
Casualty estimates vary: between 750,000 and two million people died
of the virus worldwide (34,000 people in the United States) during the
two years (1968-1969) that it was active. It was therefore the least
lethal pandemic in the 20th century.
