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.

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

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.

"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.

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%.

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.

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.

Symptoms of endemic typhus include headache, fever, muscle pain, joint pain, nausea and vomiting. 40–50% of patients will develop a discrete rash six days after the onset of signs. Up to 45% will develop neurological signs such as confusion, stupor, seizures or imbalance.

Symptoms may resemble those of measles, rubella, or possibly Rocky Mountain spotted fever. These symptoms are likely caused by a vasculitis caused by the rickettsia.

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

The diagnosis of relapsing fever can be made on blood smear as evidenced by the presence of spirochetes. Other spirochete illnesses (Lyme disease, syphilis, leptospirosis) do not show spirochetes on blood smear. Although considered the gold standard, this method lacks sensitivity and has been replaced by PCR in many settings.

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.

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.

Rocky Mountain spotted fever (RMSF), also known as blue disease, is the most lethal and most frequently reported rickettsial illness in the United States. It has been diagnosed throughout the Americas. Some synonyms for Rocky Mountain spotted fever in other countries include “tick typhus,” “Tobia fever” (Colombia), “São Paulo fever” or “"febre maculosa"” (Brazil), and “"fiebre manchada"” (Mexico). It is distinct from the viral tick-borne infection, Colorado tick fever. The disease is caused by "Rickettsia rickettsii", a species of bacterium that is spread to humans by "Dermacentor" ticks. Initial signs and symptoms of the disease include sudden onset of fever, headache, and muscle pain, followed by development of rash. The disease can be difficult to diagnose in the early stages, and without prompt and appropriate treatment it can be fatal.

The name “Rocky Mountain spotted fever” is something of a misnomer. The disease was first identified in the Rocky Mountain region, but beginning in the 1930s, medical researchers realized that it occurred in many other areas of the United States. It is now recognized that the disease is broadly distributed throughout the contiguous United States and occurs as far north as Canada and as far south as Central America and parts of South America. Between 1981 and 1996, the disease was reported from every state of the United States except for Hawaii, Vermont, Maine, and Alaska.

Rocky Mountain spotted fever remains a serious and potentially life-threatening infectious disease. Despite the availability of effective treatment and advances in medical care, approximately three to five percent of patients who become ill with Rocky Mountain spotted fever die from the infection. However, effective antibiotic therapy has dramatically reduced the number of deaths caused by Rocky Mountain spotted fever. Before the discovery of tetracycline and chloramphenicol during the latter 1940s, as many as 30% of those infected with "R. rickettsii" died.

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.

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.

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

Q fever is a disease caused by infection with "Coxiella burnetii", a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, including cats and dogs. The infection results from inhalation of a spore-like small-cell variant, and from contact with the milk, urine, feces, vaginal mucus, or semen of infected animals. Rarely, the disease is tick-borne. The incubation period is 9–40 days. Humans are vulnerable to Q fever, and infection can result from even a few organisms. The bacterium is an obligate intracellular pathogenic parasite.

The characteristic symptoms of dengue are sudden-onset fever, headache (typically located behind the eyes), muscle and joint pains, and a rash. The alternative name for dengue, "breakbone fever", comes from the associated muscle and joint pains. The course of infection is divided into three phases: febrile, critical, and recovery.

The febrile phase involves high fever, potentially over , and is associated with generalized pain and a headache; this usually lasts two to seven days. Nausea and vomiting may also occur. A rash occurs in 50–80% of those with symptoms in the first or second day of symptoms as flushed skin, or later in the course of illness (days 4–7), as a measles-like rash. A rash described as "islands of white in a sea of red" has also been observed. Some petechiae (small red spots that do not disappear when the skin is pressed, which are caused by broken capillaries) can appear at this point, as may some mild bleeding from the mucous membranes of the mouth and nose. The fever itself is classically biphasic or saddleback in nature, breaking and then returning for one or two days.

In some people, the disease proceeds to a critical phase as fever resolves. During this period, there is leakage of plasma from the blood vessels, typically lasting one to two days. This may result in fluid accumulation in the chest and abdominal cavity as well as depletion of fluid from the circulation and decreased blood supply to vital organs. There may also be organ dysfunction and severe bleeding, typically from the gastrointestinal tract. Shock (dengue shock syndrome) and hemorrhage (dengue hemorrhagic fever) occur in less than 5% of all cases of dengue, however those who have previously been infected with other serotypes of dengue virus ("secondary infection") are at an increased risk. This critical phase, while rare, occurs relatively more commonly in children and young adults.

The recovery phase occurs next, with resorption of the leaked fluid into the bloodstream. This usually lasts two to three days. The improvement is often striking, and can be accompanied with severe itching and a slow heart rate. Another rash may occur with either a maculopapular or a vasculitic appearance, which is followed by peeling of the skin. During this stage, a fluid overload state may occur; if it affects the brain, it may cause a reduced level of consciousness or seizures. A feeling of fatigue may last for weeks in adults.

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

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.

Typically, people infected with dengue virus are asymptomatic (80%) or have only mild symptoms such as an uncomplicated fever. Others have more severe illness (5%), and in a small proportion it is life-threatening. The incubation period (time between exposure and onset of symptoms) ranges from 3 to 14 days, but most often it is 4 to 7 days. Therefore, travelers returning from endemic areas are unlikely to have dengue if fever or other symptoms start more than 14 days after arriving home. Children often experience symptoms similar to those of the common cold and gastroenteritis (vomiting and diarrhea) and have a greater risk of severe complications, though initial symptoms are generally mild but include high fever.

The infection has a slow onset with fever, malaise, headache and muscular pains, very similar to Malaria symptoms. Petechiae (blood spots) on the upper body and bleeding from the nose and gums are observed when the disease progresses to the hemorrhagic phase, usually within seven days of onset.

It is caused by the bacteria "Rickettsia typhi", and is transmitted by the fleas that infest rats. While rat fleas are the most common vectors, cat fleas and mouse fleas are less common modes of transmission. These fleas are not affected by the infection. Human infection occurs because of flea-fecal contamination of the bites on human skin. Rats, cats, opossums maintain the rickettsia colonization by providing it with a host for its entire life cycle. Rats can develop the infection, and help spread the infection to other fleas that infect them, and help multiply the number of infected fleas that can then infect humans.

Less often, endemic typhus is caused by "Rickettsia felis" and transmitted by fleas carried by cats or opossums.

In the United States of America, murine typhus is found most commonly in southern California, Texas and Hawaii. In some studies, up to 13% of children were found to have serological evidence of infection.

Typical symptoms of streptococcal pharyngitis (also known as strep throat):

- Sore throat, painful swallowing

- Fever - typically over 39 °C (102.2 °F)

- Fatigue

- Enlarged and reddened tonsils with yellow or white exudates present (this is typically an exudative pharyngitis)

- Enlarged and tender lymph nodes usually located on the front of the neck

The following symptoms will usually be absent: cough, hoarseness, runny nose, diarrhea, and conjunctivitis. Their presence indicates it is more likely a viral infection.