Glossary of Important Terms

Acute respiratory distress syndrome A serious reaction to various forms of injuries to the lung. Persons developing ARDS are critically ill, often with multisystem organ failure. Hospitalization is required.
Adamantanes A class of drugs used to treat influenza. Amantadine and rimantadine are two of these drugs. Some influenza viruses are resistant to some of the drugs in this class.
Adjuvant A compound that stimulates a nonspecific immune response. Adjuvants act to accelerate, prolong, or enhance antigen-specific immune responses when used in combination with specific vaccine antigens.
Antibiotic A medication that kills bacteria.
Antibodies A protein produced by a plasma cell in the lymphatic system or bone marrow. An antibody binds to the specific antigen that has stimulated the immune system. Once bound, the antigen can be destroyed by other cells of the immune system.
Antigen A substance, foreign to the body, that stimulates the production of antibodies by the immune system. Antigens include foreign proteins, bacteria, viruses, pollen and other materials.
Antigenic drift A modest change in the antigens of a virus during reproduction, usually the result of a copying error. Some immunity may persist. (also see antigentic drift graphic in SCIENCE chapter)
Antigenic shift A dramatic change in the antigens of a virus, which may occur for several reasons (see antigenic shift graphic in SCIENCE chapter). No immunity persists.
Antiviral A medication that inactivates viruses.
Avian flu A broad term that refers to influenza in birds, which may be caused by any number of viral subtypes, not just H5N1.
Epidemic An intense, greater-than-expected outbreak of disease over a local or wide geographic area
Face mask Disposable masks, cleared by the FDA for use as medical devices. Such masks include masks labeled as surgical, dental, medical procedure, isolation, or laser. They serve to help stop droplets from being spread by the person wearing them but are not designed to protect against breathing in small-particle aerosols that may contain viruses.
H5N1 A subtype of avian flu that was first identified in poultry in 1997 in Hong Kong and successfully jumped the species barrier to infect and kill humans, albeit rarely; H5N1 was the major source of renewed concerns about a possible flu pandemic in recent years.
2009 H1N1 A novel swine flu that was first identified in two unrelated children in California and subsequently identified as the cause of influenza among patients worldwide. The virus contains a unique combination of genes from Eurasian swine, avian, and classical swine influenza viruses and is substantially different from human influenza A (H1N1).
Hemagglutinin An enzyme that governs the ability of the influenza virus to bind to and enter cells, where multiplication of the virus then occurs.
HPAI High-pathogenic avian influenza. Describes any flu virus that causes much illness and death among birds. For example, there are several high-pathogenic versions of H5 and H7 avian flu viruses. (See LPAI.)
Immunofluorescence The labeling of antibodies or antigens with fluorescent dyes, which makes them visible when looking through a microscope.
Incubation period The time between infection and the onset of illness or first symptoms of illness.
Infectious period The time during which ill patients can transmit the disease.
Influenza Also called flu. A contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The only way to prevent it is through vaccination.
Isolation The separation of persons who have a specific infectious illness from those who are healthy and the restriction of their movement to stop the spread of that illness.
LPAI Low-pathogenic avian influenza. The majority of avian fluviruses are LPAI viruses, which cause little or mild illness among birds.
Neuraminidase An enzyme that governs the release of newly formed influenza virus from the cells.
Oseltamivir An antiviral drug used to treat influenza. The trade name for the drug is Tamiflu.
Pandemic An epidemic that sweeps over the globe (from the Greek for all and peoplepan demos).
Pneumonia An inflammation of the lungs, which is usually caused by bacteria or viruses, and may develop secondary to flu.
Quarantine The separation and restriction of movement of persons who, while not yet ill, have been exposed to an infectious agent and therefore may become infectious.
Reassortment A process by which viral genes from different strains or species are reassembled to form a new virus. The 2009 influenza A (H1N1) was produced by so called reassortment events.
Resistance The ability of a virus or antibiotic to render previously effective drug treatment ineffective. Resistance usually occurs because not all micro-organisms are equally susceptible to drug treatment. Those that survive pass on their ability to their progeny. Improper use of antivirals or antibiotics contributes significantly to the rise of resistance.
Respirator A kind of mask that protects the wearer from the environment, including flu viruses. N95 respirators must be carefully fitted, worn and disposed of to provide maximum effectiveness.
Strain With respect to flu viruses, a variation of a single subtype, e.g. there are different strains of H5N1 and H1N1.
Type With respect to flu viruses, one of three broad categories: A, B or C. Subtypes of influenza A are further designated by their hemagglutinin and neuraminidase antigens, e.g. H1N1, H3N2, etc.
Vaccination Any biological preparation intended to produce immunity to a disease by stimulating the production of antibodies. Vaccines contain an agent that resembles a microorganism and stimulates the body's immune system to recognize the agent as foreign, destroy it, and "remember" it, so that the immune system can more easily recognize and destroy any of these microorganisms later.
Ventilator A mechanical device that automatically moves air into and out of the lungs. Used to treat patients with severe cases of flu or pneumonia, as well as other conditions that affect the lungs.
Zanamivir An antiviral drug used to treat influenza. The trade name is Relenza.