H1N1 virus , UPSC PRELIMS 2015

First go through the text (given after the questions) and then attempt the questions

QUES.  H1N1 virus is sometimes mentioned in the news with reference to which one of the following diseases?
(a) AIDS
(b) Bird flu
(c) Dengue
(d) Swine flu

ANSWER . (d) Swine flu

H1N1 virus

In virology, influenza A virus subtype H1N1 (A/H1N1) is the subtype of Influenza A virus that was the most common cause of human influenza (flu) in 2009, and is associated with the 1918 flu pandemic.

It is an orthomyxovirus that contains the glycoproteins haemagglutinin and neuraminidase. For this reason, they are described as H1N1, H1N2 etc. depending on the type of H or N antigens they express with metabolic synergy.

Haemagglutinin causes red blood cells to clump together and binds the virus to the infected cell. Neuraminidase is a type of glycoside hydrolase enzyme which helps to move the virus particles through the infected cell and assist in budding from the host cells.

Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. Other strains of H1N1 are endemic in pigs (swine influenza) and in birds (avian influenza).

Swine influenza is an infection caused by any one of several types of swine influenza viruses. Swine influenza virus (SIV) or swine-origin influenza virus (S-OIV) is any strain of the influenza family of viruses that is endemic in pigs. As of 2009, the known SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3.