In today’s column, I’ll be doing a quick rundown on common terms used in relation to infection.
CONTAGION is the transmission of a disease from a sick person to a susceptible individual. INFECTIOUS DISEASES are those caused by pathogens or harmful organisms or microorganisms like viruses, bacteria, fungus, protozoa, and bigger ones like helminths or worms.
In layman’s terms, all these pathogens or disease-causing organisms are collectively called GERMS.
COMMUNICABLE diseases are those that are transmissible from one human to another; CONTAGIOUS diseases are communicable diseases which are MORE EASILY TRANSMITTED from one person to another. ZOONOTIC diseases are infectious diseases that humans contract or acquire from animal sources.
A SPORADIC disease is an illness that occurs only OCCASIONALLY within the population of a particular geographic area (town, province, barangay), whereas an ENDEMIC disease is one that is ALWAYS present within that population. A good example is goiter which is endemic to certain areas of the Cordillera because of the paucity or lack of iodine sources crucial in the synthesis of thyroid hormones.
EPIDEMIC diseases are those that occur in a greater-than-usual number of cases in a particular region (country and its nearby neighbors), usually occurring within a worrisome short period of time.
A PANDEMIC disease is one that occurs in epidemic proportions in many countries SIMULTANEOUSLY, WORLDWIDE. The 1918 Spanish flu pandemic was the most devastating illness of the 20th century, killing more than 20 million worldwide; thus, it has become the catastrophe against which all pandemics of modern times are measured.
As a standard procedure by the World Health Organization (WHO), pandemics like flu are named after the point of origin or first recognition, like the Hong Kong flu, or where the variant of a virus was first identified, like the UK or the alpha variant of the SARs-Cov2 virus.
The sources of microbes or germs that cause infectious diseases are many and varied. They are known as RESERVOIRS which may be a living host or even inanimate objects or materials where the pathogen can multiply or merely survive until it is transferred to a susceptible host.
Living reservoirs include humans, household pets, farm animals, certain insects, and arachnids like ticks and mites, with these hosts not suffering from a disease brought by “transient boarders.”
Inanimate reservoirs include air, soil, dusts, food, milk, and FOMITES (inanimate objects, personal property or possessions of a patient like their handkerchief, comb, slippers, towels, as well as items found in healthcare facilities like beddings, gowns, eating and drinking utensils, hospital equipment such as bedpans, stethoscopes, latex gloves and other clinical gadgets and apparatus). Even telephones, doorknobs, and computer keyboards in clinics are fomites that may be contaminated by microorganisms and contribute to the spread of disease.
VECTORS are animals, mostly arthropods, which are commonly associated with human infection, including insects (mosquitoes, biting flies, lice, fleas) and arachnids (mites and ticks). The arthropods vector may first take a blood meal from an infected person or animal, then bites and eventually transfers the pathogen to a healthy individual. Examples very close to our minds is the female biting Aedes aegypti mosquito that spreads dengue fever or that pesky female Anopheles flavirostris mosquito that brings the plasmodium parasites that cause malaria.
CARRIERS are persons who are colonized—the microbe is in their bodies—with a particular pathogen, but the microbe is NOT CURRENTLY causing disease in them. However, asymptomatic as they are, the pathogen can be transmitted by the carrier to other persons who may become ill. Incubatory carriers are those capable of transmitting the disease before symptoms appear, while convalescent carriers are those who can transmit the disease while in the first few days of their recovery.
Isolation is a quarantine procedure designed to prevent a sick person from infecting others, like an active TB patient having a room to himself to avoid infecting his family. REVERSE ISOLATION IS keeping a sick person away from others who might infect him some more as exemplified by HIV patients whose immunity is so low, even a cold virus from a visitor could eventually led to a deadly bout with pneumonia caused by Pneumocystis jirovecii (formerly carinii).
