The following signs and symptoms refer to epidemic typhus as it is the most important of the typhus group of diseases.

Signs and symptoms begin with sudden onset of fever, and other flu-like symptoms about one to two weeks after being infected. Five to nine days after the symptoms have started, a rash typically begins on the trunk and spreads to the extremities. This rash eventually spreads over most of the body, sparing the face, palms, and soles. Signs of meningoencephalitis begin with the rash and continue into the second or third weeks. Other signs of meningoencephalitis include sensitivity to light (photophobia), altered mental status (delirium), or coma. Untreated cases are often fatal.

Multiple diseases include the word "typhus" in their description. Types include:

Classically, the course of untreated typhoid fever is divided into four distinct stages, each lasting about a week. Over the course of these stages, the patient becomes exhausted and emaciated.

- In the first week, the body temperature rises slowly, and fever fluctuations are seen with relative bradycardia (Faget sign), malaise, headache, and cough. A bloody nose (epistaxis) is seen in a quarter of cases, and abdominal pain is also possible. A decrease in the number of circulating white blood cells (leukopenia) occurs with eosinopenia and relative lymphocytosis; blood cultures are positive for "Salmonella" Typhi or "S. paratyphi". The Widal test is usually negative in the first week.

- In the second week, the person is often too tired to get up, with high fever in plateau around and bradycardia (sphygmothermic dissociation or Faget sign), classically with a dicrotic pulse wave. Delirium is frequent, often calm, but sometimes agitated. This delirium gives to typhoid the nickname of "nervous fever". Rose spots appear on the lower chest and abdomen in around a third of patients. Rhonchi are heard in lung bases.

- The abdomen is distended and painful in the right lower quadrant, where borborygmi can be heard. Diarrhea can occur in this stage: six to eight stools in a day, green, comparable to pea soup, with a characteristic smell. However, constipation is also frequent. The spleen and liver are enlarged (hepatosplenomegaly) and tender, and liver transaminases are elevated. The Widal test is strongly positive, with antiO and antiH antibodies. Blood cultures are sometimes still positive at this stage.

- (The major symptom of this fever is that the fever usually rises in the afternoon up to the first and second week.)

- In the third week of typhoid fever, a number of complications can occur:

- Intestinal haemorrhage due to bleeding in congested Peyer's patches; this can be very serious, but is usually not fatal.

- Intestinal perforation in the distal ileum: this is a very serious complication and is frequently fatal. It may occur without alarming symptoms until septicaemia or diffuse peritonitis sets in.

- Encephalitis

- Respiratory diseases such as pneumonia and acute bronchitis

- Neuropsychiatric symptoms (described as "muttering delirium" or "coma vigil"), with picking at bedclothes or imaginary objects.

- Metastatic abscesses, cholecystitis, endocarditis, and osteitis

- The fever is still very high and oscillates very little over 24 hours. Dehydration ensues, and the patient is delirious (typhoid state). One-third of affected individuals develop a macular rash on the trunk.

- Platelet count goes down slowly and risk of bleeding rises.

- By the end of third week, the fever starts subsiding

Symptoms include severe headache, a sustained high fever, cough, rash, severe muscle pain, chills, falling blood pressure, stupor, sensitivity to light, delirium and death. A rash begins on the chest about five days after the fever appears, and spreads to the trunk and extremities. A symptom common to all forms of typhus is a fever which may reach 39 °C (102 °F).

Brill-Zinsser disease, first described by Nathan Brill in 1913 at Mount Sinai Hospital in New York City, is a mild form of epidemic typhus which recurs in someone after a long period of latency (similar to the relationship between chickenpox and shingles). This recurrence often occurs in times of relative immunosuppression, which is often in the context of malnutrition and other illnesses. In combination with poor sanitation and hygiene which leads to a greater density of lice, this reactivation is why typhus forms epidemics in times of social chaos and upheaval.

Yellow fever begins after an incubation period of three to six days. Most cases only cause a mild infection with fever, headache, chills, back pain, fatigue, loss of appetite, muscle pain, nausea, and vomiting. In these cases, the infection lasts only three to four days.

In 15% of cases, however, people enter a second, toxic phase of the disease with recurring fever, this time accompanied by jaundice due to liver damage, as well as abdominal pain. Bleeding in the mouth, the eyes, and the gastrointestinal tract cause vomit containing blood, hence the Spanish name for yellow fever, "vómito negro" ("black vomit"). There may also be kidney failure, hiccups, and delirium.

The toxic phase is fatal in about 20 to 50% of cases, making the overall fatality rate for the disease about 3.0 to 7.5%. However, the fatality rate of those with the toxic phase of the disease may exceed 50%.

Surviving the infection provides lifelong immunity, and normally no permanent organ damage results.

Typhoid fever, also known simply as typhoid, is a bacterial infection due to "Salmonella" typhi that causes symptoms. Symptoms may vary from mild to severe and usually begin six to thirty days after exposure. Often there is a gradual onset of a high fever over several days. Weakness, abdominal pain, constipation, and headaches also commonly occur. Diarrhea is uncommon and vomiting is not usually severe. Some people develop a skin rash with rose colored spots. In severe cases there may be confusion. Without treatment, symptoms may last weeks or months. Other people may carry the bacterium without being affected; however, they are still able to spread the disease to others. Typhoid fever is a type of enteric fever along with paratyphoid fever.

The cause is the bacterium "Salmonella" typhi, also known as "Salmonella enterica" serotype Typhi, growing in the intestines and blood. Typhoid is spread by eating or drinking food or water contaminated with the feces of an infected person. Risk factors include poor sanitation and poor hygiene. Those who travel to the developing world are also at risk and only humans can be infected. Diagnosis is by either culturing the bacteria or detecting the bacterium's DNA in the blood, stool, or bone marrow. Culturing the bacterium can be difficult. Bone marrow testing is the most accurate. Symptoms are similar to that of many other infectious diseases. Typhus is a different disease.

A typhoid vaccine can prevent about 30% to 70% of cases during the first two years. The vaccine may have some effect for up to seven years. It is recommended for those at high risk or people traveling to areas where the disease is common. Other efforts to prevent the disease include providing clean drinking water, better sanitation, and better handwashing. Until it has been confirmed that an individual's infection is cleared, the individual should not prepare food for others. Treatment of disease is with antibiotics such as azithromycin, fluoroquinolones or third generation cephalosporins. Resistance to these antibiotics has been developing, which has made treatment of the disease more difficult.

In 2015, there were 12.5 million new cases worldwide. The disease is most common in India. Children are most commonly affected. Rates of disease decreased in the developed world in the 1940s as a result of improved sanitation and use of antibiotics to treat the disease. Each year in the United States, about 400 cases are reported and it is estimated that the disease occurs in about 6,000 people. In 2015, it resulted in about 149,000 deaths worldwide – down from 181,000 in 1990 (about 0.3% of the global total). The risk of death may be as high as 20% without treatment. With treatment, it is between 1 and 4%. The name typhoid means "resembling typhus" due to the similarity in symptoms.

Epidemic typhus is a form of typhus so named because the disease often causes epidemics following wars and natural disasters. The causative organism is "Rickettsia prowazekii", transmitted by the human body louse ("Pediculus humanus humanus").

Paratyphoid fever resembles typhoid fever. Infection is characterized by a sustained fever, headache, abdominal pain, malaise, anorexia, a nonproductive cough (in early stage of illness), a relative bradycardia (slow heart rate), and hepatosplenomegaly (an enlargement of the liver and spleen). About 30% of Caucasians develop rosy spots on the central body. In adults, constipation is more common than diarrhea.

Only 20% to 40% of people initially have abdominal pain. Nonspecific symptoms such as chills, sweating, headache, loss of appetite, cough, weakness, sore throat, dizziness, and muscle pains are frequently present before the onset of fever. Some very rare symptoms are psychosis (mental disorder), confusion, and seizures.

Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains particularly in the back, and headaches. Symptoms typically improve within five days. In about 15% of people within a day of improving, the fever comes back, abdominal pain occurs, and liver damage begins causing yellow skin. If this occurs, the risk of bleeding and kidney problems is also increased.

The disease is caused by the yellow fever virus and is spread by the bite of an infected female mosquito. It infects only humans, other primates, and several species of mosquitoes. In cities, it is spread primarily by "Aedes aegypti", a type of mosquito found throughout the tropics and subtropics. The virus is an RNA virus of the genus "Flavivirus". The disease may be difficult to tell apart from other illnesses, especially in the early stages. To confirm a suspected case, blood sample testing with polymerase chain reaction is required.

A safe and effective vaccine against yellow fever exists and some countries require vaccinations for travelers. Other efforts to prevent infection include reducing the population of the transmitting mosquito. In areas where yellow fever is common and vaccination is uncommon, early diagnosis of cases and immunization of large parts of the population is important to prevent outbreaks. Once infected, management is symptomatic with no specific measures effective against the virus. Death occurs in up to half of those who get severe disease.

In 2013, yellow fever resulted in about 127,000 severe infections and 45,000 deaths, with nearly 90% of these occurring in Africa. Nearly a billion people live in an area of the world where the disease is common. It is common in tropical areas of South America and Africa, but not in Asia. Since the 1980s, the number of cases of yellow fever has been increasing. This is believed to be due to fewer people being immune, more people living in cities, people moving frequently, and changing climate. The disease originated in Africa, from where it spread to South America through the slave trade in the 17th century. Since the 17th century, several major outbreaks of the disease have occurred in the Americas, Africa, and Europe. In the 18th and 19th centuries, yellow fever was seen as one of the most dangerous infectious diseases. In 1927 yellow fever virus became the first human virus to be isolated.

The disease is classically a five-day fever of the relapsing type, rarely exhibiting a continuous course. The incubation period is relatively long, at about two weeks. The onset of symptoms is usually sudden, with high fever, severe headache, pain on moving the eyeballs, soreness of the muscles of the legs and back, and frequently hyperaesthesia of the shins. The initial fever is usually followed in a few days by a single, short rise but there may be many relapses between periods without fever. The most constant symptom is pain in the legs. Recovery takes a month or more. Lethal cases are rare, but in a few cases "the persistent fever might lead to heart failure". Aftereffects may include neurasthenia, cardiac disturbances and myalgia.

After an incubation period around seven days, the disease manifests abruptly with chills, high fevers, muscular and articular pains, severe headache, and photophobia. The location of the bite forms a black ulcerous crust (tache noire). Around the fourth day of the illness, a widespread rash appears, first macular and then maculopapular and sometimes petechial.

"Bartonella quintana" is transmitted by contamination of a skin abrasion or louse-bite wound with the faeces of an infected body louse ("Pediculus humanus corporis"). There have also been reports of an infected louse bite passing on the infection.

Paratyphoid fever, also known simply as paratyphoid, is a bacterial infection caused by one of the three types of "Salmonella enterica". Symptoms usually begin six to thirty days after exposure and are the same as those of typhoid fever. Often there is a gradual onset of a high fever over several days. Weakness, loss of appetite, and headaches also commonly occur. Some people develop a skin rash with rose colored spots. Without treatment symptoms may last weeks or months. Other people may carry the bacteria without being affected; however, are still able to spread the disease to others. Both typhoid and paratyphoid are of similar severity. Paratyphoid fever is a type of enteric fever along with typhoid fever.

Paratyphoid is caused by the bacteria "Salmonella enterica" of the serotype Paratyphi A, Paratyphi B or Paratyphi C growing in the intestines and blood. They are usually spread by eating or drinking food or water contaminated with the feces of an infected person. They may occur when a person who prepares food is infected. Risk factors include poor sanitation as is found among poor crowded populations. Occasionally they may be transmitted by sex. Humans are the only animal infected. Diagnosis may be based on symptoms and confirmed by either culturing the bacteria or detecting the bacteria's DNA in the blood, stool, or bone marrow. Culturing the bacteria can be difficult. Bone marrow testing is the most accurate. Symptoms are similar to that of many other infectious diseases. Typhus is an unrelated disease.

While there is no vaccine specifically for paratyphoid, the typhoid vaccine may provide some benefit. Prevention includes drinking clean water, better sanitation, and better handwashing. Treatment of the disease is with antibiotics such as azithromycin. Resistance to a number of other previously effective antibiotics is common.

Paratyphoid affects about 6 million people a year. It is most common in parts of Asia and rare in the developed world. Most cases are due to Paratyphi A rather than Paratyphi B or C. In 2015 paratyphoid fever resulted in about 29,200 deaths down from 63,000 deaths in 1990. The risk of death is between 10% and 15% without treatment while with treatment it may be less than one percent.

A few days after the infective bite, a feeling of lassitude, abdominal distress and chills develop followed by fever of 39 °C to 40 °C, severe frontal headaches, muscle and joint aches, flushing of the face and a fast heart rate. After two days the fever begins to subside and the temperature returns to normal. Fatigue, a slow heart rate and low blood pressure may persist from few days to several weeks but complete recovery is the rule.

African tick bite fever is often asymptomatic or mild in clinical presentation and complications are rare. The onset of illness is typically 5–7 days after the tick bite, although in some cases it may take up to 10 days for symptoms to occur. Symptoms can persist for several days to up to three weeks. Common presenting symptoms include:

- Fever

- Headache

- Muscle aches

- Inoculation eschar, which is dead, often black, tissue around a bite site (see photo above)

- Eschars may or may not be present. "Amblyomma" ticks actively attack cattle or humans and can bite more than once. In African tick bite fever, unlike what is typically seen with other Rickettsial spotted fevers when only one eschar is identified, multiple eschars may be seen and are considered pathognomonic.

- Swollen lymph nodes near the site of the bite

- Maculopapular and/or vesicular rash

Complications are rare and are not life-threatening. No deaths due to African tick bite fever have been reported. Reported complications include:

- Prolonged fever > 3 weeks in duration

- Reactive arthritis

- Moderate to severe headache

Incubation period is usually two to three weeks. The most common manifestation is flu-like symptoms with abrupt onset of fever, malaise, profuse perspiration, severe headache, muscle pain, joint pain, loss of appetite, upper respiratory problems, dry cough, pleuritic pain, chills, confusion, and gastrointestinal symptoms, such as nausea, vomiting, and diarrhea. About half of infected individuals exhibit no symptoms.

During its course, the disease can progress to an atypical pneumonia, which can result in a life-threatening acute respiratory distress syndrome, whereby such symptoms usually occur during the first four to five days of infection.

Less often, Q fever causes (granulomatous) hepatitis, which may be asymptomatic or becomes symptomatic with malaise, fever, liver enlargement, and pain in the right upper quadrant of the abdomen. Whereas transaminase values are often elevated, jaundice is uncommon. Retinal vasculitis is a rare manifestation of Q fever.

The chronic form of Q fever is virtually identical to inflammation of the inner lining of the heart (endocarditis), which can occur months or decades following the infection. It is usually fatal if untreated. However, with appropriate treatment, the mortality falls to around 10%.

The diagnosis is made with serologic methods, either the classic Weil-Felix test

(agglutination of Proteus OX strains ), ELISA, or immunofluorescence assays in the bioptic material of the primary lesion.

A spotted fever is a type of tick-borne disease which presents on the skin. They are all caused by bacteria of the genus "Rickettsia". Typhus is a group of similar diseases also caused by "Rickettsia" bacteria, but spotted fevers and typhus are different clinical entities.

The phrase apparently originated in Spain in the seventeenth century and was ‘loosely applied in England to typhus or any fever involving petechial eruptions.’ During the seventeenth and eighteenth centuries, it was thought to be ‘“cousin-germane” to and herald of the bubonic plague’, a disease which periodically afflicted the city of London and its environs during the sixteenth and seventeenth centuries, most notably during the Great Plague of 1665.

Types of spotted fevers include:

- Mediterranean spotted fever

- Rocky Mountain spotted fever

- Queensland tick typhus

- Helvetica Spotted fever

Respiratory infection in humans is relatively rare and presents as two stages. It infects the lymph nodes in the chest first, rather than the lungs themselves, a condition called hemorrhagic mediastinitis, causing bloody fluid to accumulate in the chest cavity, therefore causing shortness of breath. The first stage causes cold and flu-like symptoms. Symptoms include fever, shortness of breath, cough, fatigue, and chills. This can last hours to days. Often, many fatalities from inhalational anthrax are when the first stage is mistaken for the cold or flu and the victim does not seek treatment until the second stage, which is 90% fatal. The second (pneumonia) stage occurs when the infection spreads from the lymph nodes to the lungs. Symptoms of the second stage develop suddenly after hours or days of the first stage. Symptoms include high fever, extreme shortness of breath, shock, and rapid death within 48 hours in fatal cases. Historical mortality rates were over 85%, but when treated early (seen in the 2001 anthrax attacks), observed case fatality rate dropped to 45%. Distinguishing pulmonary anthrax from more common causes of respiratory illness is essential to avoiding delays in diagnosis and thereby improving outcomes. An algorithm for this purpose has been developed.

Depending on the site of infection, tularemia has six characteristic clinical variants: ulceroglandular (the most common type representing 75% of all forms), glandular, oropharyngeal, pneumonic, oculoglandular, and typhoidal.

The incubation period for tularemia is one to 14 days; most human infections become apparent after three to five days. In most susceptible mammals, the clinical signs include fever, lethargy, loss of appetite, signs of sepsis, and possibly death. Nonhuman mammals rarely develop the skin lesions seen in people. Subclinical infections are common, and animals often develop specific antibodies to the organism. Fever is moderate or very high, and tularemia bacilli can be isolated from blood cultures at this stage. The face and eyes redden and become inflamed. Inflammation spreads to the lymph nodes, which enlarge and may (mimicking bubonic plague). Lymph node involvement is accompanied by a high fever.

Spotted fever can be very difficult to diagnose in its early stages, and even experienced doctors who are familiar with the disease find it hard to detect.

People infected with "R. rickettsii" usually notice symptoms following an incubation period of one to two weeks after a tick bite. The early clinical presentation of Rocky Mountain spotted fever is nonspecific and may resemble a variety of other infectious and non-infectious diseases.

Initial symptoms:

- Fever

- Nausea

- Emesis (vomiting)

- Severe headache

- Muscle pain

- Lack of appetite

- Parotitis in some cases (somewhat rare)

Later signs and symptoms:

- Maculopapular rash

- Petechial rash

- Abdominal pain

- Joint pain

- Conjunctivitis

- Forgetfulness

The classic triad of findings for this disease are fever, rash, and history of tick bite. However, this combination is often not identified when the patient initially presents for care. The rash has a centripetal, or "inward" pattern of spread, meaning it begins at the extremities and courses towards the trunk.

The rash first appears two to five days after the onset of fever, and it is often quite subtle. Younger patients usually develop the rash earlier than older patients. Most often the rash begins as small, flat, pink, non-itchy spots (macules) on the wrists, forearms, and ankles. These spots turn pale when pressure is applied and eventually become raised on the skin. The characteristic red, spotted (petechial) rash of Rocky Mountain spotted fever is usually not seen until the sixth day or later after onset of symptoms, but this type of rash occurs in only 35 to 60% of patients with Rocky Mountain spotted fever. The rash involves the palms or soles in as many as 80% of the patients. However, this distribution may not occur until later on in the course of the disease. As many as 15 percent of patients may never develop a rash.

Most people who are infected develop sickness between five and 15 days after they are bitten. The symptoms may include a sudden fever, chills, headaches, muscle or joint aches, and nausea. A rash may also occur. These symptoms usually continue for two to 9 days, then disappear. This cycle may continue for several weeks if the person is not treated.

Three serotypes of Phlebovirus are known as the causative agents: Naples virus, Sicilian virus and Toscana virus.

Cutaneous anthrax, also known as Hide porter's disease, is when anthrax occurs on the skin. It is the most common form (>90% of anthrax cases). Cutaneous anthrax is also the least dangerous form of anthrax (less than 1% mortality rate with treatment). Cutaneous anthrax presents as a boil-like skin lesion that eventually forms an ulcer with a black center (eschar). The black eschar often shows up as a large, painless, necrotic ulcer (beginning as an irritating and itchy skin lesion or blister that is dark and usually concentrated as a black dot, somewhat resembling bread mold) at the site of infection. In general, cutaneous infections form within the site of spore penetration between two and five days after exposure. Unlike bruises or most other lesions, cutaneous anthrax infections normally do not cause pain. Nearby lymph nodes may become infected, reddened, swollen, and painful. A scab forms over the lesion soon, and falls off in a few weeks. Complete recovery may take longer.

Cutaneous anthrax is typically caused when "B. anthracis" spores enter through cuts on the skin. This form is found most commonly when humans handle infected animals and/or animal products.

Cutaneous anthrax is rarely fatal if treated, because the infection area is limited to the skin, preventing the lethal factor, edema factor, and protective antigen from entering and destroying a vital organ. Without treatment, about 20% of cutaneous skin infection cases progress to toxemia and death.