Microbes

John Snow is famous for his work in 1854 identifying that a cholera outbreak in London was linked to a contaminated water pump. This discovery was a foundational moment for modern epidemiology.

Antibodies are highly specific proteins that bind to unique antigens found on the surface of specific pathogens. Because of this specificity, one type of antibody cannot destroy all different types of microbes.

When antibodies bind to a microbe, they often act as a marker that makes it easier for phagocytes (a type of white blood cell) to identify and engulf the pathogen through a process called phagocytosis.

HIV (Human Immunodeficiency Virus) is caused by a virus. Impetigo and Salmonella are caused by bacteria, and cholera is also caused by a bacterium.

Chlamydia is a sexually transmitted infection caused by the bacterium Chlamydia trachomatis. Chicken pox, rabies, and polio are all caused by viruses.

Athlete's foot is a common skin infection caused by a fungus. The flu is viral, E. coli is bacterial, and malaria is caused by a protist.

The common cold is a viral infection of the upper respiratory tract. It is most commonly caused by rhinoviruses.

Polio is primarily transmitted through the fecal-oral route, which often involves contaminated water or food. Among the choices provided, water is a primary vector.

Malaria is a vector-borne disease transmitted to humans through the bite of an infected female Anopheles mosquito. Mosquitoes are animals.

Sleep is a physiological state of rest and does not involve the transmission of pathogens. Food, sexual contact, and animals are all well-documented modes of disease transmission.

An infectious disease is one that can be spread from one person to another, often caused by pathogens. Pathogen is the agent itself, not the property of being spread.

Viruses are the smallest, typically ranging from 20 to 300 nanometers. Bacteria are larger, usually in the micrometer range, and fungi are generally the largest of the three.

Bacteria have cell walls made of peptidoglycan, and fungi have cell walls made of chitin. Viruses are non-cellular and do not possess cell walls.