Hong Kong Flu

Hong Kong Flu (1968 Influenza Pandemic)

The 1968 influenza pandemic (the "Hong Kong flu") was a category 2 flu pandemic whose outbreak in 1968 and 1969 killed an estimated one million people worldwide.

Hong Kong flu was one of the famous influenza pandemics in history. It was caused by an H3N2 strain of the influenza A virus, descended from H2N2 through antigenic shift, a genetic process in which genes from multiple subtypes reassorted to form a new virus. The Hong Kong Flu (1968 pandemic influenza) H3N2 Hemagglutinin (HA) proteins and antibodies were the main research tools for this influenza pandemic.

Hong Kong Flu History

The first record of the outbreak in Hong Kong appeared on 13 July 1968. By the end of July 1968, extensive outbreaks were reported in Vietnam and Singapore. Despite the fatality of the 1957 Asian Flu in China, little improvement had been made regarding the handling of such epidemics. The Times newspaper was actually the first source to sound alarm regarding this new possible pandemic.

By September 1968, the flu reached India, Philippines, northern Australia and Europe. That same month, the virus entered California from returning Vietnam War troops but did not become widespread in the US until December 1968. It would reach Japan, Africa and South America by 1969.
The outbreak in Hong Kong, where density is about 500 people per acre, reached maximum intensity in 2 weeks, lasting 6 weeks in total from July to December 1968, however worldwide deaths from this virus peaked much later, in December 1968 and January 1969. By that time, public health warnings and virus descriptions were issued in the scientific and medical journals.

The same virus returned the following years: a year later, in late 1969 and early 1970, and in 1972.

Hong Kong Flu Symptoms

Flu symptoms lasted 4 to 5 days. Those over the age of 65 were most likely to die.

Hong Kong Flu Deaths

In comparison to other pandemics, the Hong Kong flu yielded a low death rate, with a case-fatality ratio below 0.5% making it a category 2 disease on the Pandemic Severity Index. The pandemic infected an estimated 500,000 Hong Kong residents, 15% of the population. In the United States, approximately 33,800 people died.

Fewer people died during this Hong Kong flu pandemic than the two previous influenza pandemics for various reasons: some immunity against the N2 flu virus may have been retained in populations struck by the Asian Flu strains which had been circulating since 1957; the pandemic did not gain momentum until near the winter school holidays, thus limiting the infection spreading; improved medical care gave vital support to the very ill; the availability of antibiotics that were more effective against secondary bacterial infections.

extracted from https://www.sinobiological.com/research/virus/1968-influenza-pandemic-hong-kong-flu

Hong Kong flu pandemic of 1968

1968 flu pandemic, also called Hong Kong flu pandemic of 1968 or Hong Kong flu of 1968, global outbreak of influenza that originated in China in July 1968 and lasted until 1969–70. The outbreak was the third influenza pandemic to occur in the 20th century; it followed the 1957 flu pandemic and the influenza pandemic of 1918–19. The 1968 flu pandemic resulted in an estimated one million to four million deaths, far fewer than the 1918–19 pandemic, which caused between 25 million and 50 million deaths.

The 1968 pandemic was initiated by the emergence of a virus known as influenza A subtype H3N2. It is suspected that this virus evolved from the strain of influenza that caused the 1957 pandemic. The 1957 pandemic flu virus, or influenza A subtype H2N2, is thought to have given rise to H3N2 through a process called antigenic shift, in which the hemagglutinin (H) antigen (a substance that stimulates an immune response) on the outer surface of the virus underwent genetic mutation to produce the new H3 antigen. Because the new virus retained the neuraminidase (N) antigen N2, persons who had been exposed to the 1957 virus apparently retained immune protection against the 1968 virus. This would explain the mildness of the 1968 outbreak relative to the pandemic of 1918–19.

Although the 1968 flu outbreak was associated with comparatively few deaths worldwide, the virus was highly contagious, a factor that facilitated its rapid global dissemination. Indeed, within two weeks of its emergence in July in Hong Kong, some 500,000 cases of illness had been reported, and the virus proceeded to spread swiftly throughout Southeast Asia.
Within several months it had reached the Panama Canal Zone and the United States, where it had been taken overseas by soldiers returning to California from Vietnam. By the end of December the virus had spread throughout the United States and had reached the United Kingdom and countries in western Europe. Australia, Japan, and multiple countries in Africa, eastern Europe, and Central and South America were also affected. The pandemic occurred in two waves, and in most places the second wave caused a greater number of deaths than the first wave.

The 1968 flu pandemic caused illness of varying degrees of severity in different populations. For example, whereas illness was diffuse and affected only small numbers of people in Japan, it was widespread and deadly in the United States. Infection caused upper respiratory symptoms typical of influenza and produced symptoms of chills, fever, and muscle pain and weakness. These symptoms usually persisted for between four and six days. The highest levels of mortality were associated with the most susceptible groups, namely infants and the elderly. Although a vaccine was developed against the virus, it became available only after the pandemic had peaked in many countries.

The H3N2 virus that caused the 1968 pandemic is still in circulation today and is considered to be a strain of seasonal influenza. In the 1990s a closely related H3N2 virus was isolated from pigs. Scientists suspect that the human H3N2 virus jumped to pigs; infected animals may show symptoms of swine flu.

extracted from https://www.britannica.com/event/Hong-Kong-flu-of-1968