Walking (a) Pneumonia

Background

The lungs have two major components that are crucial to the respiration process:

1. Air conducting tubular passages (the bronchi and their branching smaller bronchioles.)
2. The air exchange microscopic chambers (the alveoli)

The respiratory gases , oxygen and carbon dioxyde (the latter being the waste product of breathing) are exchanged back and forth, between the air in the alveoli and the blood circulating within the minute blood vessels present in the ultra-thin walls of the air chambers.

It clearly follows that normal respiration requires not only free passage of air into the air-chambers but also thin, unencumbered alveolar walls that can permit easy diffusion of the respiratory gases in and out of the circulating blood in the lungs.

The pneumonias

Pneumonias are infections of the lungs, in which the offending organism (i.e. bacteria, viruses, molds or other micro-organisms) trigger a substantial defense response. This defensive response , called inflammation, mobilizes to the infected organ , millions of microscopic fighters ( white blood cells) that attack and actually swallow the foreign invaders.

The trouble is that like in real wars, even friendly armies can create problems, and in the case of the pulmonary infections, the inflammatory cells may either:

1. Fill and clog the airways and the airchambers and prevent access of the inflowing air and/or interfere with the exchange of gases

or

2. Infiltrate the walls of the airchambers, and form a barrier interfering with the diffusion of gases between the air within the lungs’ chambers and the circulating blood in the thin blood vessels of the walls.

Bacterial pneumonias, including the common bronchopneumonia, are usually associated with clogging of airways and air chambers by acute inflammatory cells (“pus cells”).

Viral infections on the other hand, are generally associated with invasion of the walls of the alveoli by a different type of inflammatory cells and these cause the so called interstitial (in between tissue) pneumonia.

The severity of pneumonia depends on a number of factors including how dangerous is the infecting organism, the closeness and amount of exposure and the health condition of the patient.

The “walking pneumonia”

Walking or atypical pneumonias are pneumonias that are caused by less common micro-organisms, and most of them are caused by Mycoplasma, an extremely tiny microscopic organism related to bacteria.

The pneumonia is called “walking pneumonia” because in most cases the disease is not severe enough to confine the patient to bed or to warrant hospitalization.

Mycoplasma pneumonia affects primarily adults below 40 years of age and children.

Mycoplasma infections occur year round but are more common in late summer and fall.

Mycoplasma pneumonia is infectious and is spread through contact with droplets expelled from the nose and throat of affected people when they sneeze or cough.

Generally the transmission of the disease requires a relatively prolonged close contact with an infected person, and most transmissions occur within families. However, every four to eight years, Mycoplasma pneumonia epidemics may occur and involve as many as 50% of all pneumonias.

Symptoms begin about 15-25 days after being exposed to an infected person, and develop gradually over the next two to four days.

Typical symptoms may include fever, chills, excessive sweating, sore throat, a cough that may or may not be productive, malaise and occasional chest pain.Symptoms may persist for a few days to more than a month.

Occasionally, the Mycoplasma pneumonia may be associated with a painful ear infection, anemia or skin rashes. The disease is usually relatively mild, but occasionally individual symptoms may be quite distressing with the patients feeling generally much worse than they look.

Diagnostic tests may reveal increased concentrations of certain immune substances (cold agglutininns) but a definite diagnosis of Mycoplasma infection, requires more complicated serological tests which are not usually done unless they are part of a research protocol or for diagnostic purposes of suspected epidemics.

The outlook for most treated patients is excellent as the infection responds well to Erythromycin and Tetracyclines. (Tetracyclines are usually not recommended in patients under 7 years of age, because it may cause yellowing of the permanent teeth.) An untreated Mycoplasma pneumonia, in most cases will resolve spontaneously, but may easily drag on over a couple of months or more.

Immunity after mycoplasma infections does occur but it is not life long and its exact duration is unknown. Recurrent infections are usually much milder than the original episode.

Currently there are no vaccines for the prevention of Mycoplasma infection and the only way of averting the associated walking pneumonia is to avoid being exposed to the sneezing or coughing of infected patients.