The Hong Kong flu in 1968 was a category 2 pandemic of H3N2 influenza, a new flu strain at the time that is estimated to have killed a million people worldwide during the pandemic. Sino Biological traces the origin of the virus to a genetic mutation in an H2N2 strain of the flu virus, which caused a flu pandemic starting in Asia approximately 10 years prior.
The first cases of Hong Kong flu
The first case of H3N2 influenza, and the start of the 1968-1969 pandemic, occurred in Hong Kong in July 1968. The virus quickly spread in Asia, reaching Australia and Europe by Sept. 1968, and finally Africa and South America in 1969. Cases first appeared in the United States in Sept. 1968 and were widespread in the country by December of that year. The same virus circulated in the population at the end of 1969 and early 1970, and then again in 1972. Though the pandemic virus ran its course in Hong Kong over approximately six weeks, the death toll peaked over the winter of 1968-1969.
Hong Kong flu deaths 1968 – 1969
The fatality rate of this pandemic flu strain was actually much lower than that of other pandemic strains. Sino Biological cites a case-fatality ratio of less than 0.5 percent, though 15 percent of Hong Kong residents, approximately half a million people, were infected. More than 33,000 deaths in the United States during the outbreak were attributed to the Hong Kong flu according to Flu.gov. People over the age of 65 years were more likely to succumb to the viral infection and its complications, but a combination of new medical advances in the mid-20th century and the winter holiday for schoolchildren reduced the effect of the pandemic.
Hong Kong flu symptoms
The symptoms of infection with the H3N2 Hong Kong flu of 1968 lasted 4 to 5 days. Human influenza A viruses like H3N2 share a similar set of symptoms caused by the infection in the respiratory system and the response of the immune system to the presence of the virus. Not everyone with the flu has a fever, but feeling feverish or having chills is considered a common symptom, as well as cough, sore throat, runny or stuffy nose, headache, muscle ache and fatigue or tiredness. Children may also have gastrointestinal symptoms, including nausea, vomiting and diarrhea. If a person does have a fever, it is over 100 degrees Fahrenheit.
The potential complications of the flu include pneumonia, bronchitis and ear or sinus infections. The availability of antibiotics in 1968 reduced the number of deaths from secondary bacterial infections, which can lead to the complications, compared to earlier pandemics.
The place of Hong Kong flu in history
The H3N2 flu strain that emerged in 1968 was just one step in the mutation of influenza to the strains involved in outbreaks and pandemics today. The recombination of multiple sub-types from previous pandemics caused a resurgence of disease that was countered by the immunity of the populace and advanced medical treatments. Hong Kong flu is generally considered to have been the third, final and mildest notable flu pandemic of the 20th century. But it was just the beginning for the discovery of new influenza strains in humans, including the H1N1 strain of recent outbreaks.
