STD and ecological niches


The bald eagle is making a comeback following near extinction from the insidious effects of DDT on the environment. Environmental awareness in the United States is growing, and people are becoming aware of the close interrelationship between the plants and animals of any given habitat. These relationships extend to the microscopic world of viruses, bacteria, fungi, and parasites, which are organisms that are much more difficult to see and often more difficult to understand. While we are becoming aware of the environment around us, we often fail to understand the environment within us.

A habitat is host to the plants and animals that live within it. In a successful habitat a balance is struck from the bottom of the food chain to the top, such that each participant has its place and its effects, all juggled in a complex relationship.

Humans (or any animal or plant for that matter) are much the same as a small habitat. We are host to a large number of viruses, bacteria, fungi, and parasites that are part of our NORMAL flora and fauna. In other words, these creatures are found in normal humans and do not produce disease; in fact, some of these may actually benefit humans. Examples of beneficial organisms are the intestinal bacteria that produce Vitamin B12 and vitamin K. Viruses, bacteria, fungi, and parasites that cause illness are called disease-causing organisms or pathogens, and are not part of our normal flora and fauna.

Living things have a strong drive (not necessarily a conscious thing) to reproduce. This drive is no less for virus and bacteria than it is for higher animals. Virus, bacteria, fungi, or parasites have several requirements to be successful in their drive to reproduce:

1. They must be ensured of a way of passing from host to host.
2. They must survive host defenses long enough to be guaranteed of making that passage
3. They should maintain the health of the host for as long as possible, so they have a greater likelihood of being passed on many times.

In these three areas, sexually transmitted diseases (STDs) excel, for the following reasons.
1. Sex between humans is governed by one of nature’s basic drives. Sex has and will always be present and it is often difficult to “just say NO.” Sex is such a strong drive that it often clouds judgment, certainly a benefit to any STD.
2. Most STDs have a long residence time in humans before they are eradicated by host defenses. Gonorrhea, an STD with one of the shortest residence times (2 to 5 weeks) but a high rate of transmission, is a very successful STD that depends on the guaranteed high frequency of sex between humans. Gonorrhea is the most frequently reported infectious disease in the United States. Syphilis has one of the longest residence times of any STD, causing disease and increasing disability often for more than 20 years in an individual.
3. Most STDs do not kill their host. Although herpes is a lifelong infection, it does not destroy the host. Syphilis may ultimately destroy its host, but only more than 20 years after infection. AIDS is the only STD that consistently kills its host and even then requires 10 to 12 years to do so. AIDS has the added bonus of not causing apparent disease for the first 5 to 10 years, so individuals may be unaware they are infected and subsequently do not change their sexual behavior, further guaranteeing spread of the organism.

Sexually transmitted diseases fit into the ecology of the human host habitat just as the coyote and jackrabbit fit into the sagebrush habitat of the West or the alligator and the wild boar fit into the swamp habitat of the Everglades. Understanding the nature of STDs, their mode of transfer, and their effects on health will help each of us individually avoid becoming infected and infecting others. Sexual health is just that, sexual experience between humans without fear of disease or health consequences.

Johns Hopkins patient information

Last revised: December 4, 2012
by Harutyun Medina, M.D.

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