A History of Influenza A(H1N1)

1976 US outbreak

On February 5, 1976, an army recruit at Fort Dix said he felt tired and weak. He died the next day and four of his fellow soldiers were later hospitalized. Two weeks after his death, health officials announced that swine flu was the cause of death and that this strain of flu appeared to be closely related to the strain involved in the 1918 flu pandemic. Alarmed public-health officials decided that action must be taken to head off another major pandemic, and they urged President Gerald Ford that every person in the US be vaccinated for the disease. The vaccination program was plagued by delays and public relations problems, but about 24% of the population had been vaccinated by the time the program was canceled.

About 500 cases of Guillain-Barre syndrome, resulting in death from severe pulmonary complications for 25 people, were probably caused by an immunopathological reaction to the 1976 vaccine. Other influenza vaccines have not been linked to Guillain-Barré syndrome, though caution is advised for certain individuals, particularly those with a history of GBS.

2007 Philippine outbreak

On August 20, 2007 Department of Agriculture officers investigated the outbreak of swine flu in Nueva Ecija and Central Luzon, Philippines. The mortality rate is less than 10% for swine flu, if there are no complications like hog cholera. On July 27, 2007, the Philippine National Meat Inspection Service (NMIS) raised a hog cholera "red alert" warning over Metro Manila and 5 regions of Luzon after the disease spread to backyard pig farms in Bulacan and Pampanga, even if these tested negative for the swine flu virus.

2009 swine flu outbreak

In March and April 2009, more than 1,000 cases of swine flu in humans were detected in Mexico, and more than 80 deaths are suspected to have a connection with the virus. As of April 25, 2009 19:30 EDT there are 11 laboratory confirmed cases in the southwestern United States and in Kansas, and several suspected cases in the New York City metropolitan area. Following a series of reports of isolated cases of swine flu,  the first announcement of the outbreak in Mexico was documented on April 23, 2009. Some of the cases have been confirmed by the World Health Organization to be due to a new genetic strain of H1N1. The new strain has been confirmed in 16 of the deaths and 44 others are being tested as of April 24, 2009. The Mexican fatalities are said to be mainly young adults, a hallmark of pandemic flu.

At 8 p.m. on Sunday, April 26, the New Zealand Minister of Health confirmed that 22 students returning from a school trip from Mexico had flu-like symptoms (most likely swine flu). 13 of the students with flu-like symptoms were tested and 10 tested positive for Influenza A, their cases strongly suspected to be the swine flu strain. However there is a possibility that the infected are not infected with the swine flu but other forms of the flu. The government has suggested that citizens of New Zealand with flu-like symptoms should see their physician immediately.

There have been five cases of possible swine flu in Canada, according to the Canadian Press. Two are in British Columbia, and three in Nova Scotia. According to the provincial government, four students in Windsor, Nova Scotia have confirmed cases of swine flu.

The new strain appears to be a recombinant between two older strains. Preliminary genetic characterization found that the hemagglutinin (HA) gene was similar to that of swine flu viruses present in US pigs since 1999, but the neuraminidase (NA) and matrix protein (M) genes resembled versions present in European swine flu isolates. Viruses with this genetic makeup had not previously been found to be circulating in humans or pigs, but there is no formal national surveillance system to determine what viruses are circulating in pigs in the US

On April 26, 2009, some schools in the United States announced closures and cancellations related to possibilities that students may have been exposed to swine flu.

According to University of Virginia virologist Frederick Hayden, the most recent flu season was dominated by H1N1 viruses, and people who had received flu shots in the US may have some protection against swine flu.


 

[source:eBeijing.gov.cn]