The symptoms of diphtheria usually begin two to seven days after infection. Symptoms of diphtheria include fever of 38 °C (100.4 °F) or above, chills, fatigue, bluish skin coloration (cyanosis), sore throat, hoarseness, cough, headache, difficulty swallowing, painful swallowing, difficulty breathing, rapid breathing, foul-smelling and bloodstained nasal discharge, and lymphadenopathy. Within two to three days, diphtheria may destroy healthy tissues in the respiratory system. The dead tissue forms a thick, gray coating that can build up in the throat or nose. This thick gray coating is called a “pseudomembrane.” It can cover tissues in the nose, tonsils, voice box, and throat, making it very hard to breathe and swallow. Symptoms can also include cardiac arrhythmias, myocarditis, and cranial and peripheral nerve palsies.

Laryngeal diphtheria can lead to a characteristic swollen neck and throat, or "bull neck". The swollen throat is often accompanied by a serious respiratory condition, characterized by a brassy or "barking" cough, stridor, hoarseness, and difficulty breathing, and historically referred to variously as "diphtheritic croup", "true croup", or sometimes simply as "croup". Diphtheritic croup is extremely rare in countries where diphtheria vaccination is customary. As a result, the term "croup" nowadays most often refers to an unrelated viral illness that produces similar but milder respiratory symptoms.

Croup is characterized by a "barking" cough, stridor, hoarseness, and difficulty breathing which usually worsens at night. The "barking" cough is often described as resembling the call of a seal or sea lion. The stridor is worsened by agitation or crying, and if it can be heard at rest, it may indicate critical narrowing of the airways. As croup worsens, stridor may decrease considerably.

Other symptoms include fever, coryza (symptoms typical of the common cold), and indrawing of the chest wall–known as Hoover's sign. Drooling or a very sick appearance indicate other medical conditions, such as epiglottitis.

Common signs and symptoms include:

- sore throat

- red, swollen tonsils

- pain when swallowing

- high temperature (fever)

- headache

- tiredness

- chills

- a general sense of feeling unwell (malaise)

- white pus-filled spots on the tonsils

- swollen lymph nodes (glands) in the neck

- pain in the ears or neck

- weight loss

- difficulty ingesting and swallowing meal/liquid intake

- difficulty sleeping

Less common symptoms include:

- nausea

- fatigue

- stomach ache

- vomiting

- furry tongue

- bad breath (halitosis)

- voice changes

- difficulty opening the mouth (trismus)

- loss of appetite

- Anxiety/fear of choking

In cases of acute tonsillitis, the surface of the tonsil may be bright red and with visible white areas or streaks of pus.

Tonsilloliths occur in up to 10% of the population frequently due to episodes of tonsillitis.

Viral croup is usually a self-limiting disease, with half of cases resolving in a day and 80% of cases in two days. It can very rarely result in death from respiratory failure and/or cardiac arrest. Symptoms usually improve within two days, but may last for up to seven days. Other uncommon complications include bacterial tracheitis, pneumonia, and pulmonary edema.

Tonsillitis is inflammation of the tonsils, typically of rapid onset. It is a type of pharyngitis. Symptoms may include sore throat, fever, enlargement of the tonsils, trouble swallowing, and large lymph nodes around the neck. Complications include peritonsillar abscess.

Tonsillitis is most commonly caused by a viral infection, with about 5% to 40% of cases caused by a bacterial infection. When caused by the bacterium group A streptococcus, it is referred to as strep throat. Rarely bacteria such as "Neisseria gonorrhoeae", "Corynebacterium diphtheriae", or "Haemophilus influenzae" may be the cause. Typically the infection is spread between people through the air. A scoring system, such as the Centor score, may help separate possible causes. Confirmation may be by a throat swab or rapid strep test.

Treatment efforts involve improving symptoms and decreasing complications. Paracetamol (acetaminophen) and ibuprofen may be used to help with pain. If strep throat is present the antibiotic penicillin by mouth is generally recommended. In those who are allergic to penicillin, cephalosporins or macrolides may be used. In children with frequent episodes of tonsillitis, tonsillectomy modestly decreases the risk of future episodes.

About 7.5% of people have a sore throat in any three-month period and 2% of people visit a doctor for tonsillitis each year. It is most common in school aged children and typically occurs in the fall and winter months. The majority of people recover with or without medication. In 40% of people, symptoms resolve within three days, and in 80% symptoms resolve within one week, regardless of if streptococcus is present. Antibiotics decrease symptom duration by approximately 16 hours.

Symptoms include sudden fever with sore throat, headache, loss of appetite, and often neck pain. Within two days of onset an average of four or five (but sometimes up to twenty) 1 to 2 mm diameter grayish lumps form and develop into vesicles with red surrounds, and over 24 hours these become shallow ulcers, rarely larger than 5 mm diameter, that heal in one to seven days. These lesions most often appear on the tonsillar pillars (adjacent to the tonsils), but also on the soft palate, tonsils, uvula, or tongue.

A small number of lesions (usually 2 - 6) form in the back area of the mouth, particularly the soft palate or tonsillar pillars. The lesions progress initially from red macules to vesicles and lastly to ulcerations which can be 2 – 4 mm in size.

Pharyngitis is a type of inflammation, most commonly caused by an upper respiratory tract infection. It may be classified as acute or chronic. Acute pharyngitis may be catarrhal, purulent or ulcerative, depending on the causative agent and the immune capacity of the affected individual. Chronic pharyngitis may be catarrhal, hypertrophic or atrophic.

Tonsillitis is a sub type of pharyngitis. If the inflammation includes both the tonsils and other parts of the throat, it may be called pharyngotonsillitis. Another sub classification is nasopharyngitis (the common cold).

These comprise about 40–80% of all infectious cases and can be a feature of many different types of viral infections.

- Adenovirus – the most common of the viral causes. Typically the degree of neck lymph node enlargement is modest and the throat often does not appear red, although it is painful.

- Orthomyxoviridae which cause influenza – present with rapid onset high temperature, headache and generalized ache. A sore throat may be associated.

- Infectious mononucleosis ("glandular fever") caused by the Epstein–Barr virus. This may cause significant lymph gland swelling and an exudative tonsillitis with marked redness and swelling of the throat. The heterophile test can be used if this is suspected.

- Herpes simplex virus can cause multiple mouth ulcers.

- Measles

- Common cold: rhinovirus, coronavirus, respiratory syncytial virus, parainfluenza virus can cause infection of the throat, ear, and lungs causing standard cold-like symptoms and often pain.

A diagnosis can be made from clinical signs and symptoms, and treatment consists of minimizing the discomfort of symptoms. It can be differentiated from herpetic gingivostomatitis by the positioning of vesicles - in herpangina, they are typically found on the posterior oropharynx, as compared to gingivostomatitis where they are typically found on the anterior oropharynx and the mouth.

Diphtheritic stomatitis is a recently discovered disease and has thus far been reported only in Yellow-eyed penguins ("Megadyptes antipodes"). Its symptoms are similar to human diphtheria and is characterized by infecteous lesions in the mouth area that impede swallowing and cause respiratory troubles. The infection is caused by "Corynebacterium amycolatum", an aerobic Gram-positive bacterium and mainly affects very young chicks. However, it seems likely that a triggering agent (e.g. a virus) might be involved in which renders the corynebacterium a secondary pathogen.

The disease has been a serious cause of mortality in the 2002 and 2004 Yellow-eyed penguin breeding seasons. It seems that only the New Zealand South Island and Stewart Island/Rakiura were affected.

Acute infection with virus is associated with acute viral hepatitis, an illness that begins with general ill-health, loss of appetite, nausea, vomiting, body aches, mild fever, and dark urine, and then progresses to development of jaundice. It has been noted that itchy skin has been an indication as a possible symptom of all hepatitis virus types. The illness lasts for a few weeks and then gradually improves in most affected people. A few people may have a more severe form of liver disease known as (fulminant hepatic failure) and may die as a result. The infection may be entirely asymptomatic and may go unrecognized.

Chronic infection with virus either may be asymptomatic or may be associated with a chronic inflammation of the liver (chronic hepatitis), leading to cirrhosis over a period of several years. This type of infection dramatically increases the incidence of hepatocellular carcinoma (HCC; liver cancer). Across Europe, hepatitis B and C cause approximately 50% of hepatocellular carcinomas. Chronic carriers are encouraged to avoid consuming alcohol as it increases their risk for cirrhosis and liver cancer. virus has been linked to the development of membranous glomerulonephritis (MGN).

Symptoms outside of the liver are present in 1–10% of HBV-infected people and include serum-sickness–like syndrome, acute necrotizing vasculitis (polyarteritis nodosa), membranous glomerulonephritis, and papular acrodermatitis of childhood (Gianotti–Crosti syndrome). The serum-sickness–like syndrome occurs in the setting of acute , often preceding the onset of jaundice. The clinical features are fever, skin rash, and polyarteritis. The symptoms often subside shortly after the onset of jaundice but can persist throughout the duration of acute . About 30–50% of people with acute necrotizing vasculitis (polyarteritis nodosa) are HBV carriers. HBV-associated nephropathy has been described in adults but is more common in children. Membranous glomerulonephritis is the most common form. Other immune-mediated hematological disorders, such as essential mixed cryoglobulinemia and aplastic anemia have been described as part of the extrahepatic manifestations of HBV infection, but their association is not as well-defined; therefore, they probably should not be considered etiologically linked to HBV.

Hepatitis B is an infectious disease caused by the hepatitis B virus (HBV) that affects the liver. It can cause both acute and chronic infections. Many people have no symptoms during the initial infection. Some develop a rapid onset of sickness with vomiting, yellowish skin, tiredness, dark urine and abdominal pain. Often these symptoms last a few weeks and rarely does the initial infection result in death. It may take 30 to 180 days for symptoms to begin. In those who get infected around the time of birth 90% develop chronic while less than 10% of those infected after the age of five do. Most of those with chronic disease have no symptoms; however, cirrhosis and liver cancer may eventually develop. These complications result in the death of 15 to 25% of those with chronic disease.

The virus is transmitted by exposure to infectious blood or body fluids. Infection around the time of birth or from contact with other people's blood during childhood is the most frequent method by which hepatitis B is acquired in areas where the disease is common. In areas where the disease is rare, intravenous drug use and sexual intercourse are the most frequent routes of infection. Other risk factors include working in healthcare, blood transfusions, dialysis, living with an infected person, travel in countries where the infection rate is high, and living in an institution. Tattooing and acupuncture led to a significant number of cases in the 1980s; however, this has become less common with improved sterility. The viruses cannot be spread by holding hands, sharing eating utensils, kissing, hugging, coughing, sneezing, or breastfeeding. The infection can be diagnosed 30 to 60 days after exposure. The diagnosis is usually confirmed by testing the blood for parts of the virus and for antibodies against the virus. It is one of five known hepatitis viruses: A, B, C, D, and E.

The infection has been preventable by vaccination since 1982. Vaccination is recommended by the World Health Organization in the first day of life if possible. Two or three more doses are required at a later time for full effect. This vaccine works about 95% of the time. About 180 countries gave the vaccine as part of national programs as of 2006. It is also recommended that all blood be tested for hepatitis B before transfusion and condoms be used to prevent infection. During an initial infection, care is based on the symptoms that a person has. In those who develop chronic disease, antiviral medication such as tenofovir or interferon may be useful; however, these drugs are expensive. Liver transplantation is sometimes used for cirrhosis.

About a third of the world population has been infected at one point in their lives, including 343 million who have chronic infections. Another 129 million new infections occurred in 2013. Over 750,000 people die of hepatitis B each year. About 300,000 of these are due to liver cancer. The disease is now only common in East Asia and sub-Saharan Africa where between 5 and 10% of adults are chronically infected. Rates in Europe and North America are less than 1%. It was originally known as "serum hepatitis". Research is looking to create foods that contain HBV vaccine. The disease may affect other great apes as well.

Ludwig's angina is a fascial space infection with bilateral involvement of the submandibular, sublingual and submental spaces. The external signs may include bilateral lower facial edema around the mandible and upper neck. Intraoral signs may include a raised floor of mouth due to sublingual space involvement and posterior displacement of the tongue. Symptoms may include dysphagia, pain with swallowing, difficulty breathing, and pain.

Ludwig's angina should be treated urgently due to the airway being compromised. The infection may rapidly spread to other fascial spaces of the head and neck, further compromising the airway.

Symptoms in eosinophilc myocarditis are highly variable. They tend to reflect the many underlying disorders causing eosinophil dysfunction as well as the widely differing progression rates of cardiac damage. Before cardiac symptoms are detected, some 66% of cases have symptoms of a common cold and 33% have symptoms of asthma, rhinitis, urticarial, or other allergic disorder. Cardiac manifestations of eosinophilic myocarditis range from none to life-threatening conditions such as cardiogenic shock or sudden death due to abnormal heart rhythms. More commonly the presenting cardiac symptoms of the disorder are the same as those seen in other forms of heart disease: chest pain, shortness of breath, fatigue, chest palpitations, light headedness, and syncope. In its most extreme form, however, eosinophilic myocarditis can present as acute necrotizing eosinophilic myocarditis, i.e. with symptoms of chaotic and potentially lethal heart failure and heart arrhythmias. This rarest form of the disorder reflects a rapidly progressive and extensive eosinophilic infiltration of the heart that is accompanied by massive myocardial cell necrosis.

Hypereosinophilia (i.e. blood eosinophil counts at or above 1,500 per microliter) or, less commonly, eosinophilia (counts above 500 but below 1,500 per microliter) are found in the vast majority of cases of eosinophilic myocarditis and are valuable clues that point to this rather than other types of myocarditis or myocardial injuries. However, elevated blood eosinophil counts may not occur during the early phase of the disorder. Other, less specific laboratory findings implicate a cardiac disorder but not necessarily eosinophilic myocarditis. These include elevations in blood markers for systemic inflammation (e.g. C reactive protein, erythrocyte sedimentation rate), elevations in blood markers for cardiac injury (e.g. creatine kinase, troponins); and abnormal electrocardiograms ( mostly ST segment-T wave abnormalities).

Ludwig's angina, otherwise known as angina ludovici, is a serious, potentially life-threatening cellulitis, or connective tissue infection, of the floor of the mouth, usually occurring in adults with concomitant dental infections and if left untreated, may obstruct the airways, necessitating tracheostomy. It is named after the German physician Wilhelm Friedrich von Ludwig who first described this condition in 1836. Other names include "angina Maligna" and "Morbus Strangularis".

Ludwig's angina should not be confused with "angina pectoris", which is also otherwise commonly known as ""angina"". The word ""angina"" comes from the Greek word ἀγχόνη "ankʰónē", meaning "strangling". In this case, Ludwig's angina refers to the feeling of strangling, not the feeling of chest pain, though there may be chest pain in Ludwig's angina if the infection spreads into the retrosternal space.

The life-threatening nature of this condition generally necessitates surgical management with involvement of critical care physicians such as those found in an intensive care unit.

Eosinophilic coronary periarteritis is a heart disorder caused by extensive eosinophilic infiltration of the adventitia and periadventitia, i.e. the soft tissues, surrounding the coronary arteries. The intima, tunica media, and tunica intima layers of these arteries remain intact and are generally unaffected. Thus, this disorder is characterized by episodes of angina, particularly Prinzmetal's angina, and sudden death due to heart dysfunction. The disorder is considered distinct from eosinophilic myocarditis.

During the latest outbreak of the disease (2004), several treatment methods were tested. Main treatment involved the administration of antibiotics, in some cases glucose solution or dietary mixtures were additionally supplemented. Outcome of the different treatment methods varied greatly. Especially the success of antibiotic treatment and a widespread use on wild animals remains a matter of debate.

The main presentation of the syndrome is significant, acute pain in the chest, along with tenderness and some swelling of the cartilages affected, which is commonly palpable on examination. Perceived pain is often exacerbated with respiration. Although many times it can be extremely painful, to the point of being debilitating, Tietze's syndrome is considered to be a benign condition that generally resolves in 12 weeks. However, it can often be a chronic condition.

The associated chest pain may present similarly to angina pectoris, normally associated with heart disease, and can cause hyperventilation, anxiety or panic attacks, syncope (passing out), and temporary hypoesthesia (numbness) or paralysis.

Many cases of myocardial infarction (heart attack) patients have been re-considered and improperly diagnosed, due to the identical nature of the symptoms. In females, it is often misdiagnosed as mastalgia. Costochondritis symptoms are similar to Tietze's, the prime difference being that the pain radiates to the arms and shoulders in the latter.

In the early stages some patients may complain of a feeling of tightness around the teeth. Three signs/symptoms must be present to diagnose this condition:

- Severe gingival pain.

- Profuse gingival bleeding that requires little or no provocation.

- Interdental papillae are ulcerated with necrotic slough. The papillary necrosis of NUG has been described as "punched out".

Other signs and symptoms may be present, but not always.

- Oral malodor (intraoral halitosis).

- Bad taste (metallic taste).

Malaise, fever and/or cervical lymph node enlargement are rare (unlike the typical features of herpetic stomatitis). Pain is fairly well localized to the affected areas. Systemic reactions may be more pronounced in children. Cancrum oris (noma) is a very rare complication, usually in debilitated children. Similar features but with more intense pain may be seen in necrotizing periodontitis in HIV/AIDS.

Necrotizing gingivitis is part of a spectrum of disease termed necrotizing periodontal diseases. It is the most minor form of this spectrum, with more advanced stages being termed necrotizing periodontitis, necrotizing stomatitis and the most extreme, cancrum oris.

Acute necrotizing ulcerative gingivitis (ANUG) refers to the clinical onset of NUG. The word acute is used because usually the onset is sudden. Other forms of NUG may be chronic or recurrent.

Necrotizing ulcerative periodontitis (NUP) is where the infection leads to attachment loss, and involves only the gingiva, periodontal ligament and alveolar ligament. Progression of the disease into tissue beyond the mucogingival junction characterizises necrotizing stomatitis.

Membranous glomerulonephropathy (MGN) is a slowly progressive disease of the kidney affecting mostly people between ages of 30 and 50 years, usually Caucasian.

It is the second most common cause of nephrotic syndrome in adults, with focal segmental glomerulosclerosis (FSGS) recently becoming the most common.

Angina bullosa haemorrhagica (ABH) is a condition of the mucous membranes characterized by the sudden appearance of one or more blood blisters within the oral cavity.

The lesions, which may be caused by mild trauma to the mouth tissues such as hot foods, typically rupture quickly and heal without scarring or further discomfort. The condition is not serious except in rare cases where a large bulla that does not rupture spontaneously may cause airway obstruction.

The blisters usually affect the palate or oropharynx and are often long lived to the extent that patients burst them for symptomatic relief.

The condition is diagnosed on the basis of exclusion of other conditions and the typical presentation, particularly the constant presence of blood as the blister fluid. Angina bullosa haemorrhagica does not cause desquamative gingivitis.

The clinical presentation of plastic bronchitis beyond expectoration of casts includes a productive cough, dyspnea, fever and wheezing. Focal wheezing is a characteristic, if not specific, physical examination finding. If the casts completely obstruct the airway, breath sounds will be decreased and dullness will be present with percussion. With partial obstruction, a “fan sound” or “flag flapping” sound can be heard during auscultation. Bronchial casts can sometimes fill the airways of almost an entire lung, and present as an acute, life-threatening emergency.