Antibody, or immunoglobulins -- Any of the protein molecules produced by specialized immune system cells (B cells) that can recognize and bind to a particular foreign antigen. If the antigen is on the surface of a cell, this binding leads to cell aggregation and subsequent destruction. Antibodies are also referred to as immunoglobulins.

Antigen -- A substance that induces the formation of antibodies because the immune system recognized it as a threat. It may be a foreign substance from the environment, such as chemicals, or formed within the body, such as bacterial or viral toxins.

Attenuation -- The reduction of the virulence of a pathogenic organism, usually by adaptation to another host or to a different culture medium.

Culture -- To grow bacteria in a special medium, such as agar, which allows for their rapid reproduction. The term can also refer to the colony of bacteria resulting from this process, or to the laboratory cultivation of living tissue cells.

Encephalitis -- Inflammation of the brain usually caused by a virus. Symptoms include headache, neck pain, drowsiness, nausea, and fever.

Harmattan -- A dry, hot wind, prevailing on the Atlantic coast of Africa, in December, January, and February, blowing from the interior or Sahara. It is usually accompanied by a haze which obscures the sun.

Hepatitis -- Inflammation of the liver, usually due to a viral disease, that exists in three variants, A, B, and C. Hepatitis A is a self-limited disease caused by the hepatitis A virus, which is more prevalent is areas of poor hygiene and low socioeconomic standards, being transmitted almost exclusively by the fecal-oral route. The incubation period is about 30 days. Most cases are not clinically apparent or have mild, flu-like symptoms. Jaundice is possible, but more common with types B and C. Hepatitis B is caused by the hepatitis B virus that is shed in all body fluids by individuals with acute or chronic infections and by asymptomatic carriers. It is transferred primarily by parenteral routes, such as blood transfusion or by sharing needles, but is also transferred through sexual contact and by mother to neonate. The incubation period is about 90 days, but can range from 40 to 180 days. Symptoms initially include fever, malaise, anorexia, nausea, and vomiting, but give way to clinical jaundice, urticaria, angiodema, or arthritis. Most patients recover completely. Hepatitis C is caused by the hepatitis C virus and is the most common form of post-transfusion hepatitis. It also follows parenteral drug abuse and is a common acute sporadic hepatitis, with approximately fifty percent of acutely infected persons developing chronic hepatitis. Chronic infection is generally mild and asymptomatic, but cirrhosis may occur.

Hookworm -- An intestinal parasite of humans that usually causes mild diarrhea and cramps. However, heavy infection can cause serious problems for newborns, children, pregnant women, and the malnourished. Persons are infected when they come into direct contact with soil contaminated with hookworm larvae, generally by walking barefoot or accidental swallowing.

Immune serum, or antiserum -- A serum that contains antibody or antibodies; it may be obtained from an animal that has been immunized either by injection of antigen into the body or by infection with microorganisms containing the antigen. Antisera may be monovalent, specific for one antigen, or polyvalent, specific for more than one antigen. See "serum."

Jaundice, or icterus -- A yellowish pigmentation of the skin, tissues, and certain body fluids caused by the deposition of bile pigments resulting from interference with normal production and discharge of bile, as in certain liver diseases, such as hepatitis, or excessive breakdown of red blood cells, as after internal hemorrhage or in various hemolytic states.

Paw-paw -- An older term for the papaya tree (Asimina triloba), or its fruit. It is found in most tropical countries, having flowers with three sepals, three petals, and numerous stamens and fleshy, edible fruit. The term "papaya" is ultimately from Spanish and obsolete Portuguese.

Poochie -- The Tamil word for insect. In the early twentieth century, public health workers in what is now India and Sri Lanka often extended the term to include parasites such as hookworm.

Quoits -- A game in which flat rings of iron or rope are pitched at a stake, with points awarded for encircling it.

Serum -- The clear yellowish fluid obtained upon separating whole blood into its solid and liquid components, often referred to as plasma; also the clear portion of any body fluid.

Typhoid fever, or enteric fever -- An acute, highly infectious disease caused by the bacillus Salmonella typhi transmitted chiefly by contaminated food or water and characterized by high fever, headache, coughing, intestinal hemorrhaging, and rose-colored spots on the skin.

Typhus fever -- Louse-borne typhus is the only rickettsial disease that can cause explosive epidemics in humans. Rickettsia prowazelkii is transmitted by human body lice infected while feeding on the blood of persons with acute typhus fever. Infected lice excrete rickettsiae when feeding on a second host. People are infected by rubbing louse fecal matter or crushed lice into a bite wound, often through scratching. Typhus fever is characterized by the sudden appearance of headaches, chills, prostration, high fever, delirium, coughing, severe muscle pain, and sensitivity to light. A rash appears, usually on or near the upper trunk, on the fifth or sixth day of infection and then spreads to the entire body, except for the face, palms and soles of the feet.

Virulence -- The degree of pathogenicity of a microorganism as indicated by the severity of the disease produced and its ability to invade the tissues of a host. It is measured experimentally by the median lethal dose or median infective dose. By extension, virulence is the competence of any infectious agent to produce pathologic effects.

Virus -- Any of a large group of submicroscopic infective agents that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, animals, or plants. Viruses typically consist of a DNA or RNA core of genetic material surrounded by a protein coat. They can be considered either as very simple microorganisms or as extremely complex molecules.

Viscerotropic -- Primarily acting on the internal organs (viscera); having a predilection for the abdominal or thoracic viscera.

Wat -- A Buddhist temple in Thailand or Cambodia.