anemia
condition resulting from a lack of hemoglobin or red blood cells, or by a loss of blood; symptoms include weakness, pallor, palpitation of the heart, and a tendency to fatigue.

arbovirus
a virus transmitted by arthropods (i.e., mosquitoes); yellow fever, dengue fever, and equine encephalitis are caused by arboviruses.

arthropod
any of a phylum of invertebrate animals that have a jointed exoskeleton and paired, jointed legs including Arachnida and Insecta; many species are important medically as parasites or as vectors of organisms capable of causing disease.

bacteria
a large group of one-celled microorganisms that multiply by fission or by forming spores; certain species cause diseases in humans.

bacterial meningitis
an inflammation of the protective membranes that surround the brain (meninges) and the spinal cord caused by a bacteria and resulting in an acute, and sometimes fatal, illness.

beriberi
a disease caused by a deficiency in thiamin (vitamin B1) and characterized by muscular paralysis, weakness, and extreme loss of weight; the epidemic form is found in areas where white (polished) rice is the staple food.

carcinogen
any substance or agent that produces cancer.

contagion
the communication of disease from one individual to another; a contagious disease.

contagious disease
a disease transmitted by contact.

cultural ecology
an approach to the study of the relations between a cultural group and the natural environment proposing that configurations of environment and technology are related to social organization.

demographic transition theory
a theory based on the historical experience of Western  industrialized countries that describes the process of change from high birth rates and death rates to low birth and death rates in a population as related to changes in economic development.

dengue fever
an infectious fever with severe pain in the head, joints, and muscles and usually a skin rash; caused by a virus transmitted by mosquitoes from the genus Aedes.

diphtheria
an acute, infectious disease of the throat caused by a bacillus bacteria, usually accompanied by a high fever and the formation of a membranous substance that hinders respiration.

disease
any deviation from or interruption in the normal structure or function of any part, organ, or system of the body manifested by a set of characteristic symptoms and signs.

dysentery
disease of the intestines that produces diarrhea.

Ebola virus
one of the most pathogenic viruses known to science spread by direct contact with the blood, secretions, organs, or semen of infected persons. The virus produces Ebola hemorrhagic fever characterized by fever, weakness, muscle pain, headache, and sore throat followed by vomiting, diarrhea, rash, internal and external bleeding, and death.

encephalitis
inflammation of the brain.

endemic
present or usually prevalent in a population or geographical area at all times.

environmental determinism
a doctrine holding that human activities are controlled by the environment.

epidemic
appearing suddenly in numbers clearly in excess of normal expectancy.

etiology
the study or theory of the factors that cause disease.

filariae
any family of threadlike, parasitic nematode worms whose larvae develop in mosquitoes and other arthropods and are transmitted to the blood and tissues of humans and other vertebrates causing diseases.

filariasis
a disease condition caused by the presence of filariae in the blood, tissues, and especially the lymph system.

greenhouse effect
the role of various trace components of the atmosphere (e.g., H₂O, CO₂,) in reabsorbing certain wavelengths of the energy spectrum radiated from the earth’s surface and thereby increasing the global temperature. This effect occurs naturally, but is augmented by human activities such as burning of fossil fuels and land cover changes since these changes emit trace gases that become further concentrated in the atmosphere (enhanced greenhouse effect). Humans have also added a new class of greenhouse gases called chlorofluorocarbons.

hanta virus
a genus of Bunyaviridae responsible for pnemonia and hemorrhagic fevers; an outbreak of the hantavirus infection causing severe and often fatal pulmonary symptoms occurred in the Four Corners region of the USA in 1993.

hemorrhagic fever
a group of diverse, severe epidemic viral infections of worldwide distribution, but occurring mainly in tropical climates, usually transmitted by to humans by arthropod bites or by contact with infected rodents; marked by fever, shock, hemorrhagic manifestations, and neurological disturbances.

hepatitis B
a viral disease resulting in inflammation of the liver; caused by the hepatitis B virus that is endemic worldwide and is transmitted through blood transfusions, needle sharing among intravenous drug users, sexual contact, and from mother to fetus.

helminth
a parasitic worm.

host
an animal or plant that harbors or nourishes another organism (parasite).

Huntington’s disease
a disease characterized by involuntary jerking or writhing of the limbs and face and mental deterioration; usually results in death within 15 years.

infectious disease
a disease by or capable of being communicated by the invasion and multiplication of microorganisms in the body tissues (infection).

lactose intolerance
the inability to digest a sugar found in milk known as lactose.

lassa fever
an acute, highly fatal infectious disease caused by a virus occurring epidemically in parts of Africa, transmitted by the multimammate rat which sheds the virus in its urine. Symptoms include fever, abdominal pain, vomiting, and fatal shock.

malaria
an infectious disease endemic to parts of Africa, Asia, Central and South America that is spread by the bite of an infected anopheline mosquito. It is characterized by high fever, shaking chills, sweating, and anemia.

natural increase
the increase in population that results from the positive difference between high birth rates and low death rates; prominent during Stage 2 and Stage 3 of the demographic transition.

onchocerciasis
an infection caused by the worm Onchocerca volvulus; characterized by a rash, thickening or wrinkling of the skin, and lesions.

paradigm
the working assumptions, procedures, and findings routinely accepted and employed by a group of people; a paradigm defines one’s world view and the approach one takes to defining, researching, and solving problems.

parasite
a plant or animal that lives upon or within another living organism.

pellagra
a condition resulting from a deficiency of niacin and characterized by dermatitis, inflammation of mucous membranes, diarrhea, and psychic disturbances.

pneumonia
a disease in which the lung becomes inflamed, often accompanied by chills, a pain in the chest, a hard dry cough, and a high fever.

protozoa
microscopic organisms, like amebas and paramecia, that belong to the Protozoa phylum of protists and which reproduce by fission.

quarantine
to confine away from others for a period of time to prevent the spread of an infectious disease.

Rift Valley fever
an acute infection of domestic animals and humans caused by a virus transmitted by mosquitoes of the Aedes, Culex, and Erethmapodites genera. In humans, it is characterized by flu-like symptoms; in severe cases it may be associated with encephalitis or hemorrhagic fever.

tuberculosis (TB)
an infectious disease caused by a species of Mycobacterium characterized by the formation of tubercules (small, rounded, granular lesions). In humans, the lung is the organ primarily infected and is the portal through which the infection spreads to other organs. Tuberculosis has a tendency to be a chronic ailment.

vector
a carrier (animal or arthropod) that transfers an infective agent from one host to another.

virulent
characterized by a rapid and severe infectious condition.

virus
one of a group of minute infectious agents characterized by a lack of an independent metabolism and by the ability to replicate only within living host cells.

whooping cough
an acute, highly contagious infection of the respiratory tract which commonly affects young children; the symptoms begin with a slight fever, and a dry cough, eventually leading to a persistent, quick cough marked by long-drawn, shrill, whooping noises resulting from spasmodic closure of the vocal chords.

yellow fever
an acute, infectious disease caused by a virus that is transmitted to humans by mosquitoes, which acquires the virus either from humans or from animals; occurs endemically and epidemically in the Americas and Africa. The disease in its severe form is marked by fever, jaundice, and kidney and liver damage.