The majority of human illnesses with known causes are produced by infectious agents. In fact, some of the greatest medical discoveries in the twentieth century have resulted in the controlling of many contagious diseases through public health measures, sanitary engineering, immunization, etc.

Although there remain some exceptions to this rule, infectious diseases as a class are more easily prevented and cured than any other major group of disorders. Yet, despite the elimination of certain infectious diseases and a profound reduction in the death statistics of others, man is by no means free of infection.

Only a modest decrease in the total effect of disease has been produced through these control measures. I am thinking primarily of smallpox vaccinations and malaria control.

Additionally, numerous new infections have resulted from the widespread use of broad spectrum antibiotics, immune suppressive agents used in transplant procedures, the progressive longevity of people with chronic degenerative disease, and high-risk lifestyles such as drug abuse and homosexuality.

Life threatening diseases that were never seen before this decade are now invading the immune deficient. These infections are termed opportunistic. There is a very complex interaction between the microorganism and man when an infectious disease occurs.

Much has been learned about the way microbes enter the body, the ways they produce injury to the tissues, and the resistance of a person (the host), as well as the mechanism of recovery. Unfortunately, though, it is often difficult to transfer much of this scientific information to help the individual patient with his infection.

It is well known that microorganisms of different species or different strains of the same species, vary widely in their capacity to produce disease. Furthermore, we know that human beings are not equally susceptible to disease caused by a given bacterium or virus.

Fortunately for us, the mere presence of an organism in the body does not always lead to clinical illness. Often there is a carrier state (like the story of Typhoid Mary) or a hidden (subclinical) infection. Several factors are involved in the mechanism of getting an infectious disease.

Most microorganisms that are capable of producing disease vary in several ways. Their virulence, that is, the degree of capability to produce illness, can be distinguished from their invasiveness, or their ability to spread and disseminate in the body. A few parasites produce toxins that account for their ability to damage body tissues.

Some organisms tend to localize in certain cells or organs and produce their damage there. Most vital, we must try to understand the natural and acquired factors that can enable a person to not only resist the invasion of organisms, but also reduce our susceptibility to disease.

The white blood cells, the antibodies, many enzymes, and environmental factors including nutrition, can affect a person’s recovery from infectious disease. There are general features that suggest infection. The abrupt onset of any illness, particularly associated with fever and chills, may well indicate an infection.

Pain in the muscles, sensitivity to light, sore throat, swelling of the lymph nodes or spleen, and upset in the digestive tract, often constitute hallmarks of infections. Many specific infectious diseases can be recognized by the “story of illness”, or medical history, in association with obvious physical findings.

Blood counts, urine testing, x-rays of the chest, and more specific laboratory procedures can be helpful in confirming the diagnosis of more difficult cases. Many organisms that cause disease can be demonstrated by a microscopic examination of properly stained preparations of sputum, spinal fluid, and other body secretions.

The microscope is indeed a most helpful laboratory instrument in the diagnosis of infections. Cultures can be obtained from the blood, sputum, urine, and other discharges. Investigation by the microbiologist, who applies appropriate tests to the germs, while growing these cultures in his incubator, will usually yield the specific infectious agent, particularly in bacterial disease.

The presence of antibodies may indicate the type of infection, and for contagious illnesses, such as tuberculosis, the skin test is very useful. All of these diagnostic procedures help to determine the cause, which then can lead one to specific therapy.

Viral Illnesses

By far, the majority of mild illnesses affecting people in their homes are caused by viruses. These conditions are usually self—limited, that is, our bodies overcome the infection and get well spontaneously. Recent advances in the science of microbiology, including the use of the electron microscope, have helped to identify most of these germs.

Viruses are nonliving organisms, different from bacteria or protozoa (one-celled animals). The virus particle is a combination of proteins and nucleic acid. They enter the cell of the host, take over its specific enzyme systems, and rapidly multiply to produce disease. Some of the more common viral infections will be discussed below.

Common Cold

More than one hundred types of viruses are known to cause the common cold. This explains why scientific attempts to produce a vaccine have been so unsatisfactory. Over 40% of respiratory illnesses in children and adults are caused by this family of organisms. Although colds occur throughout the year, there are peaks of incidence in the spring and fall.

The disease is more severe in children, especially those under two years of age. Higher fevers, cough, croup, and occasionally pneumonia occur. Family infections are more often initiated by children. They spread like gossip in schools or any setting where close contact is found.

After introducing the respiratory virus into the nose or throat, congestion, symptoms of discharge in the nose, general aching, and mild headache result. There is usually no fever. Nasal secretions increase over the period of a day or two. After a week or more, the individual has completely recovered.

A number of factors predispose to the common cold, including unwise ingestion of a large amount of sugar, and exposure to sudden changes in temperature, particularly with chilling. Negative emotions are thought to be related to host susceptibility through a change in the acidity of the nasal mucous membrane.

Such reactions as hatred, anger, fear and frustration bring about the temporary deficiency of lysozyme, a potent enzyme capable of killing many germs.

The treatment for a cold should include the general health measures for respiratory hygiene, utilizing copious intake of fluids, especially water, increased rest, steam inhalations, hot packs over the congested areas and the avoidance of close contact with other people who are susceptible to the same disease. Recovery is usually complete. Diet should be light with easily digested foods, especially fruit.

Influenza

A great deal of attention has been directed toward the prevention influenza, (an Italian word referring to the influence of heavenly bodies previously thought to cause disease). The disastrous epidemic of 1918 caused an estimated 20 to 40 million deaths from this viral disease.

Vaccinations are available annually, especially recommended for the elderly and others with a chronic debilitating illness.

Flu symptoms are of sudden onset, with headache, muscle pains, fever, and prostration.

Often a discharge from the nose, sneezing, hoarseness, cough, chest pain, and shortness of breath and or gastric symptoms make the patient feel quite ill.

The disease begins within one to three days after exposure. Like other common viral infections, antibiotics are completely ineffective.

Hot baths are very helpful and should always be followed by a cool shower, cold mitten friction and a period of bed rest.

The avoidance of usual activities and the consumption of a light diet, such as fruit, juices, and increased water intake, will help your body fight these infections.

Hot packs to the chest and steam inhalations will relieve many of the symptoms of chest pain, and aid the fight for recovery.

They help as well to control fever. Return to full activity should be gradual. Usually one infection confers immunity to that particular type of virus.

Polio

Poliomyelitis was a common acute viral infection; it occurs naturally only in human beings. Infection with the polio virus produces a wide variety of clinical manifestations. Its most severe form attacks part of the central nervous system. After an incubation period of 3 to 35 days, the poliovirus infection may assume one of four forms:

1. Inapparent infection.
2. Minor illness, such as a transient respiratory or gastrointestinal disturbance.
3. Nonparalytic Poliomyelitis, which usually produces temporary stiffness of the neck and other symptoms of spinal meningitis.
4. Paralytic poliomyelitis.

In the latter, most serious form, the virus attacks specialized cells in the spinal cord and brain stem, producing paralysis in the face or extremities. This varies from mild affliction to respiratory paralysis. Some of the most heroic medical treatments have been developed to save the lives of these respiratory polio cases, often maintaining the patient for years in an “iron lung.”

Some of the most dramatic uses of hydrotherapy have also been effective in the treatment of advanced polio cases, especially the Kenny packs, used for severe muscle spasm. Rehabilitation in a specialized setting offers maximal potential for complete recovery.

Prevention, however, is the best approach. With several vaccines available for each type of polio, childhood immunization offers an inexpensive and relatively safe medical practice to avoid this dreaded disease.

Rabies

All mammals are affected by this serious viral disease of the central nervous system. Usually, it is transmitted by accidental or traumatic inoculation with infected saliva. The bite of an animal may transfer this to humans. The urban type is propagated chiefly by unimmunized domestic dogs.

Sylvatic rabies is propagated in skunks, foxes, raccoons, wolves, and bats. When the live rabies virus is introduced through an animal bite, there will be an early infection in 1-4 days, marked by fever, headache, fatigue, nausea, vomiting, or cough. Later, encephalitis develops with excitation, confusion, hallucination, combativeness, muscle spasm, and seizures.

The latter dysfunction of brain stem centers brings the traditional picture of foaming at the mouth, followed by frank paralysis, coma, and death. Unless artificial supportive measures are instituted, the survival is seldom longer than four days! Approximately 30,000 persons in the United States and 1,000,000 in the world are treated preventively for rabies each year.

The local wound should be generously scrubbed with soap, then flushed with water or alcohol. Lacerations should not be sewed shut. Active immunization is then given with either nerve tissue derived vaccine (NTV) or duck embryo derived vaccine (DEV). When the vaccine is given alone, fourteen daily doses are sufficient.

When rabies vaccine is given with antirabies antiserum, twenty-one daily injections, followed by boosters, ten and twenty days after the initial series are required. The antirabies antiserum from human origin is best, to avoid serum sickness so common when equine (horse) serums are used.

Until recently, rabies in a human being was regarded as 100% fatal. With the advent of specific vaccines, as well as intensive cardiorespiratory assistance, for the first time in history there is hope of survival in this dreaded disease.

Gastrointestinal Viruses Although tropical diseases and food poisoning may cause sudden vomiting, nausea, and diarrhea, viral infections are very commonly the cause of these symptoms. These are usually transmitted through stool-to-mouth contact. Personal hygiene, particularly hand washing eliminates the infectious cycle.

Toddlers often bring intestinal viruses into a household. Insects, including flies and mosquitoes may act as carriers (vectors). Their incubation period lasts 2-5 days. Symptoms may be limited to the throat with soreness or tonsillar enlargement, but skin rash, and serious illness— hepatitis, viral meningitis, or pericarditis (inflammation of the pericardium)— is also seen.

Pleurodynia (pain in the pleura or coverings of the lungs) also occurs in these viral infections, as well as malaise, sore throat, anorexia, fever and severe muscle and abdominal pain. Cardiac disease brings symptoms of heart murmurs, electrocardiographic changes, and even heart failure.

By far more common, though, is the illness we termviral gastroenteritis, also called “winter vomiting” or “intestinal flu”. This disease is highly contagious; many cases are often seen in one family. Onset usually occurs within 48 hours, and recovery is rapid. Less commonly, mild diarrhea may persist for several weeks.

General measures for the treatment of any infection, including adequate fluid intake, rest, and hydrotherapy (hot packs) to relieve abdominal pain, constitute the general measures most effective in these selflimited conditions.

Hantavirus

Carried by the deer mouse (Peromyscus maniculatus) this strain of virus caused in 1993 a serious outbreak of respiratory illness. Fever, muscular aching, and cough--all resembling flu symptoms--are followed by abrupt onset of severe respiratory distress. Patients had seemed otherwise healthy.

Many (56%) of the victims died in our initial outbreak, located in the southwestern United States. Treatment was primarily supportive, with stabilization of serious cases in hospital intensive care.

To prevent Hantavirus exposure, avoid occupational or leisure activities that bring individuals into contact with infected rodents, their excreta or bites. This requires caution in harvesting field crops, sleeping in vacant cabins, cleaning barns, or living in dwellings with indoor rodent populations. Prevention is the best approach to cure.