Typhus is a group of acute infectious diseases caused by rickettsiae (microorganisms classified as an intermediate in size between bacteria and viruses) that are transmitted by arthropods (lice, fleas, mites). There are two principal forms of typhus: Endemic typhus (alternative names - Flea-borne typhus, Murine typhus, Rat typhus) and Epidemic typhus ( alternative names - Classic epidemic typhus, Human typhus, Louse-borne typhus). The disease agent for Endemic typhus is Rickettsia mooseri and for Epidemic typhus is Rickettsia prowazekii. Epidemic typhus (Louse-borne typhus) is transmitted by the body louse (Pediculus humanus) through their bites to humans and also from infected humans to louse. Epidemic typhus on the other hand, is a disease of humans and lice. It occurs mainly in temperate countries in crowded, unsanitary conditions where people don’t bathe themselves or wash their clothing. As such, people in communities especially during the cold climate are in close living conditions to keep themselves warm thus, encouraging and maintaining the spreading of lice living among humans.

Since humans are the host in epidemic typhus, this means that the conditions of war are ideal for typhus to explode into a raging epidemic disease which has been known historically to be a major killer in wartime. Typically in wars, diseases such as Typhus spreads rapidly amongst soldiers and the reasons for this is that there are usually forced to live in poor hygienic conditions (infrequent bathing and changing of clothes), mass migrations of troops (simultaneously moving in large numbers), crowding (that leads to close personal contact), inadequate housing (make shift houses), poverty (poor army maintenance) and malnutrition (undernourishment) all of which encourages the spreading of typhus more easily. Epidemic typhus is therefore a disease of war, as well as, one of famine and overcrowding. Epidemic typhus carries a large list of names that it is known by. Some of these names are: War Fever or Frebris Militarius, Camp Fever, Famine Fever, Gaol Fever, Jail Fever, Ship Fever, Spotted Fever, or el tabarillo (Spanish, red cloak), Sharp Fever, Epidemic Fever, Putrid Fever, Fourteen Day Fever, Malignant Fever, Petechial Fever, Spotted Ague, Exanthematique (French), Morbis Hungaricus, Matlazahuatl (Mexican Indian), just to name a few!

The epidemic typhus infects humans of all ages and occurs in the blood in the first day of the infection which, eventually spreads over the entire body. The incubation period is between 5 to 14 days after the first symptoms of the disease. The diseases’ typical symptoms is characterized by shivering and rigour (chills), high fever, severe headache, nausea, vomiting, transient rash, running nose, cough, malaise, stupor, constipation, and pain in the chest, back and limbs. Rash usually appears after 4 or 5 days on the trunk, the wrist or the shoulders, and under the armpit. Rash does not appear on the face or neck. The disease last between 2 - 2 ½ weeks. The patient’s fever usually disappears after 14 days provided they are no complications. A second attack of the disease is rare since the body builds an immunity for the disease. However, the disease can re-emerge in the individual that is, relapses may occur. When this occurs, it is usually known as Brill-Zinsser Disease.

Epidemic typhus for centuries have been associated with war where it is a major killer. Thus, this makes it a war disease - an important factor affecting the outcome of wars. In the 15th century Epidemic typhus made it first major appearance in Spain in 1489 during the Spanish siege of Moorish Granada which, is said to be brought in from the Eastern Mediterranean. During the war, the Spanish which had an army of 25,000 soldiers laid siege to the city by barricading the Moors inside their stronghold at Granada while suffering a lost of 3,000 men to their enemy. This outcome they hoped, would quickly bring the war campaign to a successfully end and, as a result, remove the Moslem influence on the European continent. However, to the Spaniards dismay, they were stroke by a raging epidemic disease known as epidemic typhus (louse-borne typhus) which took over the army and killed 17,000 of their men (more than half the army) which was far more than the 3,000 that they lost to their enemy. This totally devastated the Spanish army where the remaining soldiers fled, bringing back the disease with them to Spain thus, introducing the disease to many parts throughout Europe. The Christian reconquest of Spain was eventually achieved in 1492 with the fall of Granada.

In the 17th century, the Thirty Years War of 1618-1648 not surprisingly also had its share of the epidemic typhus which had its impact on wars during this era. War during this time period was a religious one among Catholics, Lutherans, Calvinists and also the rivalry between the Habsburg emperor and others (e.g. Danish, Dutch, France and Sweden). It consisted of a series of wars which raged for 30 years throughout central Europe. During this time epidemic typhus which was the dominant disease after 1630 partnered with plague where they ravaged all that came in their path. Two examples of typhus impact during this time period were: 1). Charles I, who had a superior army, was unable to march to London from his palace at Hampstead to crush the Earl of Exeter uprising due to an outbreak of typhus in his army. The second example 2); In 1632, as two armies - the Swedish king (Gustavos Adolphus) and the Catholic commander (Baron Von Wallenstein) - prepared to engage themselves in a major battle at Nuremburg, Germany, epidemic typhus stroke both armies. About 18,000 soldiers were killed on both sides from the disease and as a result of this, commanders of both armies quickly decided to withdraw their forces. Thus epidemic typhus prevented a war from taking place.

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Major Infectious Disease Causing Agents: Their Differences and the Diseases they Cause

An infectious disease-causing agent is the pathogen (living micro-organism be it bacterial, viral or parasitic) that can cause disease to its host. The major infectious disease causing agents are bacteria (germ), virus, rickettsia (louse) and parasite.

Bacteria are single-celled (unicellular) living organisms with tiny flagella (a tail like appendage that they use to swim). They are invisible to the naked eye and can only be seen with a microscope. They generally have cell walls and may appear in one of several shapes. Bacillus (rodlike), coccus (spherical or ovoid), and spiral (corkscrew or curved). They reproduce by dividing themselves into equal cells (daughter cells). This process is called binary fission. They live in and reproduce in warm, moist environments in the body and other areas where they grow quickly, causing an infection.

Many bacterial diseases generally produce inflammation, swelling and pain from nerve irritation and fever caused by increased body temperature by the body fighting the disease. Bacterial infections can usually be treated with antibiotic. Some examples of bacterial disease are: Cholera - caused by the ingestion of contaminated water and food containing the vibrio cholerae agent by excrement of an individual with the disease. A second one is Syphilis. Syphilis spread by sexual intercourse of an infected person to the sexual partner or from an infected mother to her fetus containing the disease agent Treponema pallidium. Other bacterial diseases include; Dysentery, Leprosy, Plague and Scarlet Fever just to name a few.

Viruses unlike bacteria are smaller and can only be seen using an electron microscope. They are acellular (not cellular) and are structurally very simple. This makes viruses the smallest life form existing. A virus contains a core made of one type of nuclei acid molecule, which can either be a DNA or RNA. This contains the virus's genes. The core of a virus is usually covered by a protein coat and sometimes may be encased by an additional layer (lipid (fat) membrane) called an envelop. They can be rod-shaped, sphere-shaped, or multisided.

Viruses lack the means for self-reproduction outside a host cell and depend on their host cellular system to reproduce. Thus in a sense, they are parasite of a different life form. Unlike parasites however, they are not considered to be to be truly alive. This is due to the fact that when they are outside of a living host they are inert, and are considered living when they multiply within a host cell that they infect. The virus DNA enters cells and uses its DNA to make copy of itself, similar to what the ordinary cell would do. This means that the host body cell is tricked into making many copies of the virus inside the cell host cell thus, killing the cell where the viruses then enter (infecting) other cells to repeat the process. Inside the body viruses produce toxins (poisons) that can cause rashes, aches and fevers. A Virus is very difficult to kill and cannot be killed with antibiotics like bacteria. Some examples of viral diseases are: Aids - transmitted through bodily fluid through from an infected human to another through semen, vaginal secretion, blood and the sharing of needles by the disease agent HIV 1 and HIV 11 and Smallpox - through human to human contact through sneezing and coughing by the disease agent variola. Others include Influenza, Yellow Fever and Lassa Fever just to name a few.

Rickettsia is any group of parasitic bacteria that live in arthropods (e.g. ticks, lice, fleas and mites) and can cause disease if transmitted to humans. Thus, transmission occurs through the infected arthropod vector. Rickettsiae can only survive inside cells and is spread through the bloodstream of the host. They divide (reproduce) by a process called binary fission. Therefore, Rickettsia is some where between bacteria and viruses in comparison. Rickettsia cause disease by the damaging blood vessels in various tissues and organs. Rickettsial diseases basically fall into 4 groups and some example are: 1. Typhus: epidemic typhus, scrub typhus, murine (endemic) typhus, and Brill-Zinsser disease; 2. spotted fever-Rocky Mountain spotted fever, Eastern tick-borne rickettsioses, and rickettsialpox; 3. trench fever and 4. Q fever.

Finally, parasites are organisms whose survival depends on other organisms (the host) to feed , grow and live. They live in or on the living tissue of a host organism which may cause disease to it and generally without killing the host. There are several different sizes of parasites which can be either single-celled protozoa or multi-celled parasites (e.g. worms, flukes, and insects). The infection from a parasite are often transmitted through contact with an intermediate vector or from the result of direct contact with the parasite. Some examples of parasitic infections are : Hookworm - a worm larva that hatch from eggs containing the disease agent Ancylostoma duodenal or Necator americanus found in stool of an infected organism which penetrate the skin of the victim and continue its life cycle. A second one is Malaria. Malaria is disease caused by a protozoan parasites (of disease agents; P. falciparum, P. vivax, P. ovale, and P. malariae) which is transmitted by the bite of an infected female mosquito of the genus Anopheles. Others include Schistosomiasis and Trypanoso.