Ebola is only the latest infectious disease to make its appearance in the news.
Previously there was SARS, MERS, swine flu, and bird flu. All of these viral diseases occurred in third world settings and caused considerable panic until each in its turn dwindled away and disappeared from the world stage. Why were heath officials worried about these illnesses initially? Why has each one proved to be of concern for only a short time? Should we still be concerned about a world pandemic?
The answers to these questions are in the basic formula for catching an infectious disease: the infectious agent, the host, and the environment. To catch and continue to propagate an infectious disease, all three must allow for the passing of the disease from one person to another.
The infectious agent, the bug, must be virulent (make the patient very sick), must be hard to kill, and must be easily passed from one person to another. The host, the human who is to catch the bug, must be very susceptible and in close contact with the means (air, fluids, body contact, vectors) by which the bug is passed. The host should also have poor nutrition and a weakened immune system, to pass the bug more easily.
The environment must allow for close contact with the means for spread. Overcrowding – close, continual contact – and unsanitary conditions will facilitate the spreading of the bug. And the absence of adequate health care facilities will hinder the care of patients thus infected.
The infectious agent, the ebola virus, is virulent and it is hard to kill. However, it is hard to catch – as evident by the number of people in the immediate casual vicinity of the various people in the US who have had ebola, none of whom have caught the infection. The host must be in close, continual contact with the bodily fluids of someone who is actively shedding the virus (has a fever, which indicates that the virus is multiplying in the person).
In the US culture, the only people doing so with sick patients (and got infected) were those medically caring for an infected patient. People in casual contact were not infected. The environment in the US is not generally overcrowded. Basic sanitary conditions are prevalent everywhere – clean public surfaces, water, sewage care, air filtration, food preparation. And most health care facilities can do basic isolation and several centers are prepared to do highly intensive isolation and supportive care with excellent methods to transport patients to these facilities.
Then why the high mortality (50-70%) in African countries and such low mortality (one in eight so far) in the US? Although ebola is actually hard to catch, the environment in Africa (fear of health care, close contact, poor sanitation, inadequate health care facilities, and the culture of caring for the dead) makes the passing of the infection extremely likely.
In the US, the environment – no overcrowding, wide-spread basic sanitation, and excellent health care – very effectively prevents the spread of the disease among the general population.
Yes, an epidemic anywhere in the world is cause for concern, until we understand the nature of the infection – it’s cause, how it is spread, weapons to use against it. Yes, ebola – if you catch it – makes people very sick.
But no, the environment is not right for it to spread in the US – just as it wasn’t for those other diseases. But if we ever become complacent about our excellent public health policies or about taking care of our own body’s immune system and its ability to fight off an infectious disease . . .
