Epidemic typhus

Epidemic typhus, also known as louse-borne typhus, is an acute infectious disease caused by Rickettsia prowazekii and transmitted primarily by the human body louse (Pediculus humanus corporis). The disease has historically been associated with periods of war, famine, and population displacement, where overcrowding and poor hygiene enable rapid transmission. Although responsible for millions of deaths throughout history, epidemic typhus is now considered rare, occurring chiefly in colder, mountainous regions of Central and East Africa and in parts of Central and South America. It is distinct from murine typhus, which is less severe and transmitted by fleas.

Clinical features and progression

Symptoms of epidemic typhus typically manifest within one to two weeks following exposure to the causative organism. The initial presentation is generally sudden and includes:

• Fever and chills
• Severe headache
• Myalgia and general body aches
• Cough and rapid breathing
• Nausea and vomiting
• Confusion or altered mental status

A characteristic macular rash usually appears after five to six days, beginning on the upper trunk and spreading to the remainder of the body, though it rarely involves the face, palms, or soles. If untreated, the disease may progress rapidly, leading to serious complications and a case-fatality rate of approximately 40 per cent.
A unique manifestation associated with R. prowazekii infection is Brill–Zinsser disease, a mild recrudescent form occurring years or decades after the initial infection. This relapse often arises during periods of immunosuppression or malnutrition and is of epidemiological importance because it can reinitiate outbreaks in communities experiencing social disruption and poor sanitation.

Complications

Complications may occur in severe or untreated cases and can include:

• Acute renal failure
• Kidney or bladder infections
• Encephalitis
• Myelitis
• Septic shock

These developments significantly increase morbidity and underscore the importance of prompt diagnosis and treatment.

Transmission and epidemiology

Epidemic typhus is transmitted through the faeces of infected body lice. When a louse feeds on a person carrying R. prowazekii, the bacterium proliferates in the louse’s gut and is excreted in its faeces. The pathogen enters the human body when the host scratches the itchy bite, inadvertently rubbing contaminated faeces into the skin. R. prowazekii can remain viable in dried louse faeces for many days and persists for weeks within the body of a dead louse.
Historically, epidemic typhus has flourished in environments characterised by deprivation and overcrowding. Notable examples include outbreaks in German concentration camps during the Second World War, where unhygienic conditions enabled rampant louse infestation. In modern times, situations with potential for epidemic spread include refugee camps, famine-affected regions, and areas struck by natural disasters.
In intervals between human outbreaks, the flying squirrel serves as a recognised zoonotic reservoir, allowing the bacterium to persist in nature.

Diagnosis and treatment

Diagnosis is typically confirmed using serological tests such as indirect fluorescent antibody (IFA), enzyme-linked immunosorbent assay (ELISA), or molecular detection via PCR, which generally becomes positive after around ten days.
Treatment requires the prompt use of antibiotics, with tetracycline, chloramphenicol, and doxycycline being the most commonly employed. Intravenous fluids and oxygen therapy may be necessary in severe cases. The difference between untreated and treated mortality is substantial: untreated mortality ranges from 10 to 60 per cent, whereas early antibiotic therapy typically reduces mortality to near zero.
Preventive measures focus on eliminating body lice and reducing exposure to unsanitary, overcrowded environments. Effective approaches include:

• Washing clothing and bedding in hot water
• Leaving clothes unworn for at least seven days to ensure death of lice and eggs
• Using insecticidal powders containing DDT, malathion, or permethrin
• Avoiding close contact with rodents such as rats, squirrels, and opossums, which can carry lice

Early historical accounts

Historical descriptions of epidemic typhus date back many centuries. Scholars suggest that as early as 430 BCE, the Plague of Athens may have been caused by epidemic typhus, based on clinical features such as high mortality, rapid progression, and gangrenous complications. The disease was likely documented in 1083 at La Trinità della Cava near Salerno, Italy.
By the mid-sixteenth century, Girolamo Fracastoro provided a detailed account of typhus in his treatise De Contagione et Contagiosis Morbis. During the siege of Granada in 1489, typhus decimated the besieging forces, with roughly 17,000 deaths attributed to the disease—far exceeding those caused by combat.
Typhus was prevalent in prisons throughout Europe, where it became known as gaol fever due to the overcrowded, unsanitary living conditions that favoured louse transmission. During the Black Assize of Oxford in 1577, over 510 individuals, including prominent judicial officials, died of epidemic typhus after exposure in court. Between 1577 and 1579, the outbreak killed roughly ten per cent of the English population. Gaol fever continued to cause high mortality throughout the eighteenth century, often claiming more lives than judicial executions.

Developments from the nineteenth to the mid-twentieth century

Substantial scientific progress occurred during the late nineteenth and early twentieth centuries. In 1916, Henrique da Rocha Lima identified Rickettsia prowazekii as the causative agent of epidemic typhus, naming it in honour of colleagues who died from the disease while studying it.
In 1930, Rudolf Weigl developed the first practical vaccine, using infected lice to propagate the bacterium. Although effective, this method posed significant occupational hazards. A safer and scalable vaccine-production technique using egg yolks was devised by Herald R. Cox in 1938, enabling wide distribution by the early 1940s.
Despite these advances, epidemic typhus remained a major cause of mortality during conflict, most notably in the concentration camps of the Second World War, where millions perished under conditions ideal for louse proliferation.

Nineteenth- and twentieth-century outbreaks

Epidemic typhus persisted in Europe, Asia, and the Americas into the modern period. Outbreaks were common wherever warfare, social upheaval, or inadequate hygiene enabled louse infestation. In the early twentieth century, improved public health measures, antibiotic availability, and widespread vaccination campaigns significantly reduced global incidence.
Nevertheless, epidemic typhus continues to pose a risk in areas affected by extreme poverty, displacement, and disaster. Public health strategies therefore emphasise surveillance, rapid diagnosis, vector control, and access to effective antibiotic therapy to prevent large-scale outbreaks.