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Hong Kong flu is a type of seasonal flu that is caused by a subtype of the influenza virus called H3N2. The H3N2 strain is able to infect birds and mammals, such as humans. It causes symptoms similar to that of a common cold, so people often disregard it until their conditions become worse. Hong Kong flu, however, can cause serious diseases and even lead to death if not addressed properly.
Like any other influenza virus, the H3N2 subtype has two distinct proteins on its surface. These proteins are called hemagglutinin, represented by the letter H, and neuraminidase, represented by the letter N. It is believed to have formed because of an antigenic shift, or a gene reassortment of different existing flu strains. In particular, it has been shown that the H3N2 subtype has genes from existing bird, pig, and human influenza A strains.
The H3N2 influenza A virus can cause Hong Kong Flu when it is transmitted from a person who has the virus to a person who is not immune to the virus. Transmission can occur through different routes. The most common routes are through direct contact and respiratory droplets. This means that simply being in the same room with an infected person or touching his or her things could result in the transmission of Hong Kong flu.
It is also said that the H3N2 virus can be transmitted through the gastrointestinal; hematogenous, or blood; and sexual routes. A person can get infected by eating contaminated food, undergoing a transfusion with contaminated blood, or having sexual contact with an infected person. Fetal transmission may also occur when a pregnant woman gets the virus.
Symptoms include runny nose, nasal congestion, cough, and sore throat. Headache, fever, joint and muscle aches, chills, and fatigue may present as well. Symptoms typically last about 4 to 5 days. A patient might feel so sick that he loses his appetite and feels weak. If not properly addressed, the disease can lead to pneumonia and asthma or chronic obstructive pulmonary disease (COPD) exacerbation. In children, it can result in a high fever and seizures. It also can lead to fetal developmental problems during pregnancy.
Bed rest aids in recovery and prevents further transmission of the virus. To relieve fever and pain symptoms, aspirin or paracetamol may be taken. An adequate fluid intake is essential to prevent dehydration. The doctor may give antiviral drugs, such as oseltamivir or zanamivir, if deemed appropriate.
The first world pandemic occurred between 1968 and 1969 and was believed to have caused a million deaths. This disease still holds a pandemic status because it affects multiple countries annually. The World Health Organization (WHO) considers it as a category 2 flu pandemic because it only causes a 0.1- to 0.5-percent case fatality rate. This means that for every thousand people affected by the flu, one to five die from the infection. Therefore, compared to other influenza pandemics, such as severe acute respiratory syndrome (SARS), the Hong Kong flu pandemic is considered mild.