VIRUSES

 A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. It infects all life forms, from animals and plants to microorganisms, including bacteria and archaea.
                                     A virus is made up of a core of genetic material, either DNA or RNA, surrounded by a protective coat called a capsid which is made up of protein. Sometimes the capsid is surrounded by an additional spikey coat called the envelope. Viruses are capable of latching onto host cells and getting inside them.
                 H3N2 influenza virus particles, colored transmission electron micrograph (TEM). Each virus consists of a nucleocapsid (protein coat) that surrounds a core of RNA (ribonucleic acid) genetic material. Surrounding the nucleocapsid is a lipid envelope that contains the glycoprotein spikes haemagglutinin (H) and neuraminidase (N). These viruses were part of the Hong Kong Flu pandemic of 1968-1969 that killed approximately one million people worldwide. H3N2 viruses can infect birds and mammals as well as humans. They often cause more severe infections in the young and elderly than other flu strains and can lead to increases in hospitalizations and deaths.