These include

- red skin rash usually of the face, elbows, and knees

- skin desquamation

- exanthema

- red tongue

- toxic shock syndrome

Other features include mesenteric lymphadenitis and arthritis. Kidney failure rarely occurs.

Relapses occur in up to 50% of patients.

Far East scarlet-like fever or scarlatinoid fever is an infectious disease caused by the gram negative bacillus "Yersinia pseudotuberculosis". In Japan it is called Izumi fever.

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%.

Yersinia pseudotuberculosis is a Gram-negative bacterium that causes Far East scarlet-like fever in humans, who occasionally get infected zoonotically, most often through the food-borne route. Animals are also infected by "Y. pseudotuberculosis". The bacterium is urease positive.

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

In animals, "Y. pseudotuberculosis" can cause tuberculosis-like symptoms, including localized tissue necrosis and granulomas in the spleen, liver, and lymph nodes.

In humans, symptoms of Far East scarlet-like fever are similar to those of infection with "Yersinia enterocolitica" (fever and right-sided abdominal pain), except that the diarrheal component is often absent, which sometimes makes the resulting condition difficult to diagnose. "Y. pseudotuberculosis" infections can mimic appendicitis, especially in children and younger adults, and, in rare cases, the disease may cause skin complaints (erythema nodosum), joint stiffness and pain (reactive arthritis), or spread of bacteria to the blood (bacteremia).

Far East scarlet-like fever usually becomes apparent five to 10 days after exposure and typically lasts one to three weeks without treatment. In complex cases or those involving immunocompromised patients, antibiotics may be necessary for resolution; ampicillin, aminoglycosides, tetracycline, chloramphenicol, or a cephalosporin may all be effective.

The recently described syndrome "Izumi-fever" has been linked to infection with "Y. pseudotuberculosis".

The symptoms of fever and abdominal pain mimicking appendicitis (actually from mesenteric lymphadenitis) associated with "Y. pseudotuberculosis" infection are not typical of the diarrhea and vomiting from classical food poisoning incidents. Although "Y. pseudotuberculosis" is usually only able to colonize hosts by peripheral routes and cause serious disease in immunocompromised individuals, if this bacterium gains access to the blood stream, it has an LD comparable to "Y. pestis" at only 10 CFU.

Signs and symptoms include fever, headache, muscle pain, cough, and gastrointestinal symptoms. More virulent strains of "O. tsutsugamushi" can cause hemorrhaging and intravascular coagulation. Morbilliform rash, eschar, splenomegaly, and lymphadenopathies are typical signs. Leukopenia and abnormal liver function tests are commonly seen in the early phase of the illness. Pneumonitis, encephalitis, and myocarditis occur in the late phase of illness.

Acute scrub typhus appears to improve viral loads in patients with HIV. This interaction is challenged by an "in vitro" study.

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.

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

Post-streptococcal glomerulonephritis (PSGN) is an uncommon complication of either a strep throat or a streptococcal skin infection. It is classified as a type III hypersensitivity reaction. Symptoms of PSGN develop within 10 days following a strep throat or 3 weeks following a GAS skin infection. PSGN involves inflammation of the kidney. Symptoms include pale skin, lethargy, loss of appetite, headache, and dull back pain. Clinical findings may include dark-colored urine, swelling of different parts of the body (edema), and high blood pressure. Treatment of PSGN consists of supportive care.

Acute rheumatic fever (ARF) is a complication of respiratory infections caused by GAS. The M-protein generates antibodies that cross-react with autoantigens on interstitial connective tissue, in particular of the endocardium and synovium, that can lead to significant clinical illness.

Although common in developing countries, ARF is rare in the United States, possibly secondary to improved antibiotic treatment, with small isolated outbreaks reported only occasionally. It is most common among children between 5 and 15 years old and occurs 1–3 weeks after an untreated GAS pharyngitis.

ARF is often clinically diagnosed based on Jones Criteria, which include: pancarditis, migratory polyarthritis of large joints, subcutaneous nodules, erythema marginatum, and sydenham chorea (involuntary, purposeless movement). The most common clinical finding is a migratory arthritis involving multiple joints.

Other indicators of GAS infection such as a DNAase or ASO serology test must confirm the GAS infection. Other minor Jones Criteria are fever, elevated ESR and arthralgia. One of the most serious complications is pancarditis, or inflammation of all three heart tissues. A fibrinous pericarditis can develop with a classic friction rub that can be auscultated. This will give increasing pain upon reclining.

Further endocarditis can develop with aseptic vegetations along the valve closure lines, in particular the mitral valve. Chronic rheumatic heart disease mostly affects the mitral valve, which can become thickened with calcification of the leaflets, often causing fusion of the commissures and chordae tendineae.

Other findings of ARF include erythema marginatum (usually over the spine or other bony areas) and a red expanding rash on the trunk and extremities that recurs over weeks to months. Because of the different ways ARF presents itself, the disease may be difficult to diagnose.

A neurological disorder, Sydenham chorea, can occur months after an initial attack, causing jerky involuntary movements, muscle weakness, slurred speech, and personality changes. Initial episodes of ARF as well as recurrences can be prevented by treatment with appropriate antibiotics.

It is important to distinguish ARF from rheumatic heart disease. ARF is an acute inflammatory reaction with pathognomonic Aschoff bodies histologically and RHD is a non-inflammatory sequela of ARF.

Erythema infectiosum or fifth disease is one of several possible manifestations of infection by parvovirus B19.

The name "fifth disease" comes from its place on the standard list of rash-causing childhood diseases, which also includes measles (1st), scarlet fever (2nd), rubella (3rd), Dukes' disease (4th, however is no longer widely accepted as distinct) and roseola (6th).

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.

Equine infectious anemia or equine infectious anaemia (EIA), also known by horsemen as swamp fever, is a horse disease caused by a retrovirus and transmitted by bloodsucking insects. The virus ("EIAV") is endemic in the Americas, parts of Europe, the Middle and Far East, Russia, and South Africa. The virus is a lentivirus, like human immunodeficiency virus (HIV). Like HIV, EIA can be transmitted through blood, milk, and body secretions.

Transmission is primarily through biting flies, such as the horse-fly and deer-fly. The virus survives up to 4 hours in the vector (epidemiology). Contaminated surgical equipment and recycled needles and syringes, and bits can transmit the disease. Mares can transmit the disease to their foals via the placenta.

The risk of transmitting the disease is greatest when an infected horse is ill, as the blood levels of the virus are then highest.

Scrub typhus or bush typhus is a form of typhus caused by the intracellular parasite "Orientia tsutsugamushi", a Gram-negative α-proteobacterium of family Rickettsiaceae first isolated and identified in 1930 in Japan.

Although the disease is similar in presentation to other forms of typhus, its pathogen is no longer included in genus "Rickettsia" with the typhus bacteria proper, but in "Orientia". The disease is thus frequently classified separately from the other typhi.

The usual symptoms are:

- Abdominal pain

- Bleeding under skin due to blood clotting problems

- Bleeding from mouth, nose or rectum

- Diarrhea

- Fever

- Chills

- Low blood pressure

- Nausea

- Organ failure

- Vomiting

- Shock

- Death of tissue (gangrene) causing blackening in extremities, mostly fingers, toes and nose

- Difficulty breathing

However, septicemic plague may cause death before any symptoms occur. Also, the above symptoms are common to many human illnesses, and are not considered diagnostic of any form of plague.

Acute: The acute form is a sudden onset of the disease at full-force. Symptoms include high fever, anemia (due to the breakdown of red blood cells), weakness, swelling of the lower abdomen and legs, weak pulse, and irregular heartbeat. The horse may die suddenly.

Subacute: A slower, less severe progression of the disease. Symptoms include recurrent fever, weight loss, an enlarged spleen (felt during a rectal examination), anemia, and swelling of the lower chest, abdominal wall, penile sheath, scrotum, and legs.

Chronic: The horse tires easily and is unsuitable for work. The horse may have a recurrent fever and anemia, and may relapse to the subacute or acute form even several years after the original attack.

A horse may also not appear to have any symptoms, yet still tests positive for EIA antibodies. Such a horse can still pass on the disease. According to most veterinarians, horses diagnosed EIA positive usually do not show any sign of sickness or disease.

EIA may cause abortion in pregnant mares. This may occur at any time during the pregnancy if there is a relapse when the virus enters the blood. Most infected mares will abort, however some give birth to healthy foals. Foals are not necessarily infected.

Studies indicate that there are breeds with a tolerance to EIA.

Recent studies in Brazil on living wild horses have shown that in the Pantanal, about 30% of domesticated and about 5.5% of the wild horses are chronically infected with EIA.

Fifth disease starts with a low-grade fever, headache, rash, and cold-like symptoms, such as a runny or stuffy nose. These symptoms pass, then a few days later the rash appears. The bright red rash most commonly appears in the face, particularly the cheeks. This is a defining symptom of the infection in children (hence the name "slapped cheek disease"). Occasionally the rash will extend over the bridge of the nose or around the mouth. In addition to red cheeks, children often develop a red, lacy rash on the rest of the body, with the upper arms, torso, and legs being the most common locations. The rash typically lasts a couple of days and may itch; some cases have been known to last for several weeks. Patients are usually no longer infectious once the rash has appeared.

Teenagers and adults may present with a self-limited arthritis. It manifests in painful swelling of the joints that feels similar to arthritis. Older children and adults with fifth disease may have difficulty in walking and in bending joints such as wrists, knees, ankles, fingers, and shoulders.

The disease is usually mild, but in certain risk groups it can have serious consequences:

- In pregnant women, infection in the first trimester has been linked to hydrops fetalis, causing spontaneous miscarriage.

- In people with sickle-cell disease or other forms of chronic hemolytic anemia such as hereditary spherocytosis, infection can precipitate an aplastic crisis.

- Those who are immuno-compromised (HIV/AIDS, chemotherapy) may be at risk for complications if exposed.

There are a number of symptoms of the virus. In the first 1–8 days the first phase begins. The symptoms in this phase are:

- chills

- headache

- pain in the lower and upper extremities and severe prostration

- a rash on the soft palate

- swollen glands in the neck

- appearance of blood in the eyes (conjunctival suffusion)

- dehydration

- hypotension

- gastrointestinal symptoms (symptoms relating to the stomach and intestines)

- patients may also experience effects on the central nervous system

In 1–2 weeks, some people may recover, although others might not. They might experience a focal hemorrhage in mucosa of gingival, uterus, and lungs, a papulovesicular rash on the soft palate, cervical lymphadenopathy (it occurs in the neck which that enlarges the lymph glandular tissue), and occasional neurological involvement. If the patient still has OHF after 3 weeks, then a second wave of symptoms will occur. It also includes signs of encephalitis. In most cases if the sickness does not fade away after this period, the patient will die. Patients that recover from OHF may experience hearing loss, hair loss, and behavioral or psychological difficulties associated with neurological conditions.

An exanthem or exanthema (from Greek ἐξάνθημα "exánthēma", "a breaking out") is a widespread rash usually occurring in children. An exanthem can be caused by toxins, drugs, or microorganisms, or can result from autoimmune disease.

It can be contrasted with an enanthem.

Historically, six "classical" infectious childhood exanthems have been recognized, four of which are viral. Numbers were provided in 1905.

The four viral exanthema have much in common, and are often studied together as a class. They are:

Scarlet fever, or "second disease", is associated with the bacterium "Streptococcus pyogenes". Fourth disease, a condition whose existence is not widely accepted today, was described in 1900 and is postulated to be related to the bacterium "Staphylococcus aureus".

Many other common viruses apart from the ones mentioned above can also produce an exanthem as part of their presentation, though they are not considered part of the classic numbered list:

- Varicella zoster virus (chickenpox or shingles)

- Mumps

- rhinovirus (the common cold)

- unilateral laterothoracic exanthem of childhood

- Some types of viral haemorrhagic fever are also known to produce a systemic rash of this kind during the progression of the disease.

- Tick-borne diseases like Rocky Mountain spotted fever produce a rash that may become extensive enough so as to be classified as exanthemous in as many as 90% of children with the disease.

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.

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 features of scarlet fever can differ depending on the age and race of the person. Children less than 5 years old can have atypical presentations. Children less than 3 years old can present with nasal congestion and a lower grade fever. Infants can potentially only present with increased irritability and decreased appetite.

Children who have darker skin can have a different presentation in that the redness of the skin involved in the rash and the ring of paleness around the mouth can be less obvious. Suspicion based on accompanying symptoms and diagnostic studies are important in these cases.