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Diphtheria

Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Most infections are asymptomatic or have a mild clinical course, but in some outbreaks, the mortality rate approaches 10%. Signs and symptoms may vary from mild to severe, and usually start two to five days after exposure. Symptoms often develop gradually, beginning with a sore throat and fever. In severe cases, a grey or white patch develops in the throat called a pseudomembrane. This tough, leathery membrane slowly blocks the airway. Starting with a barking cough similar to what is observed in croup, the neck may also swell, in part due to the enlargement of the facial lymph nodes. The pseudomembrane can grow to cover a wide area of the throat, leading to strangulation and death. Diphtheria can also involve the skin, eyes, or genitals, and can cause complications, including myocarditis, inflammation of nerves, kidney problems, and bleeding problems due to low levels of platelets.

Signs and symptoms
s, myocarditis, and cranial and peripheral nerve palsies. Diphtheritic croup 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. == Transmission ==
Transmission
Human-to-human transmission of diphtheria typically occurs through the air when an infected individual coughs or sneezes. Breathing in particles released from the infected individual leads to infection. Contact with any lesions on the skin can also lead to transmission of diphtheria, but this cause is uncommon. Indirect infections can occur, as well. If an infected individual touches a surface or object, the bacteria can be left behind and remain viable. Also, some evidence indicates diphtheria has the potential to be zoonotic, but this has yet to be confirmed. Corynebacterium ulcerans has been found in some animals, which would suggest zoonotic potential. ==Mechanism==
Mechanism
Diphtheria toxin (DT) is produced only by C. diphtheriae infected with a certain type of bacteriophage. Toxinogenicity is determined by phage conversion (also called lysogenic conversion); i.e., the ability of the bacterium to make DT changes as a consequence of infection by a particular phage. DT is encoded by the tox gene. Strains of corynephage are either tox+ (e.g., corynephage β) or tox− (e.g., corynephage γ). The tox gene becomes integrated into the bacterial genome. The chromosome of C. diphtheriae has two different but functionally equivalent bacterial attachment sites (attB) for integration of β prophage into the chromosome. The diphtheria toxin precursor is a protein of molecular weight 60 kDa. Certain proteases, such as trypsin, selectively cleave DT to generate two peptide chains, amino-terminal fragment A (DT-A) and carboxyl-terminal fragment B (DT-B), which are held together by a disulfide bond. ADP-ribosylation of EF-2 is reversed by giving high doses of nicotinamide (a form of vitamin B3), since this is one of the reaction's end products, and high amounts drive the reaction in the opposite direction. ==Diagnosis==
Diagnosis
The current clinical case definition of diphtheria used by the United States' Centers for Disease Control and Prevention is based on both laboratory and clinical criteria. Laboratory criteria • Isolation of C. diphtheriae from a Gram stain or throat culture from a clinical specimen. • Histopathologic diagnosis of diphtheria by Albert's stain. Toxin demonstration • In vivo tests (guinea pig inoculation): Subcutaneous and intracutaneous tests. • In vitro test: Elek's gel precipitation test, detection of tox gene by PCR, ELISA, ICA. Clinical criteria • Upper respiratory tract illness with sore throat. • Low-grade fever (above is rare). • An adherent, dense, grey pseudomembrane covering the posterior aspect of the pharynx; in severe cases, it can extend to cover the entire tracheobronchial tree. Case classification • Probable: a clinically compatible case that is not laboratory-confirmed, and is not epidemiologically linked to a laboratory-confirmed case. • Confirmed: a clinically compatible case that is either laboratory-confirmed or epidemiologically linked to a laboratory-confirmed case. Empirical treatment should generally be started in a patient in whom suspicion of diphtheria is high. ==Prevention==
Prevention
Diphtheria prevention relies primarily on vaccination with the diphtheria toxoid, an inactivated form of the toxin produced by Corynebacterium diphtheriae. Introduced in the 1920s and widely adopted after World War II, the toxoid vaccine triggers strong antitoxin immunity that prevents the severe respiratory and systemic effects of the disease. Today, it is administered as part of combination vaccines such as DTaP (for children) and Tdap or Td (for adolescents and adults), with booster doses recommended every 10 years to maintain protection. Widespread immunization has reduced diphtheria from a common childhood killer to a rare disease in most countries, though cases can still occur in areas with low vaccination coverage. Pentavalent vaccines, which vaccinate against diphtheria and four other childhood diseases simultaneously (Diphtheria, Tetanus, Pertussis (whooping cough), Hepatitis B, and Haemophilus influenzae type b (Hib)), are frequently used in disease prevention programs in developing countries by organizations such as UNICEF. ==Treatment==
Treatment
The disease may remain manageable, but in more severe cases, lymph nodes in the neck may swell, and breathing and swallowing are more difficult. People in this stage should seek immediate medical attention, as obstruction in the throat may require intubation or a tracheotomy. Abnormal cardiac rhythms can occur early in the course of the illness or weeks later, and can lead to heart failure. Diphtheria can also cause paralysis in the eye, neck, throat, or respiratory muscles. Patients with severe cases are put in a hospital intensive care unit, and given diphtheria antitoxin (consisting of antibodies isolated from the serum of horses that have been challenged with diphtheria toxin). Antibiotics have not been demonstrated to affect the healing of local infection in diphtheria patients treated with antitoxin. Antibiotics are used in patients or carriers to eradicate C. diphtheriae, and prevent its transmission to others. The Centers for Disease Control and Prevention (CDC) recommends either: • MetronidazoleErythromycin is given (orally or by injection) for 14 days (40 mg/kg per day with a maximum of 2 g/d), or • Procaine penicillin G is given intramuscularly for 14 days (300,000 U/d for patients weighing 10 kg); patients with allergies to penicillin G or erythromycin can use rifampin or clindamycin. In cases that progress beyond a throat infection, diphtheria toxin spreads through the blood and can lead to potentially life-threatening complications that affect other organs, such as the heart and kidneys. Damage to the heart caused by the toxin affects the heart's ability to pump blood or the kidneys' ability to clear wastes. It can also cause nerve damage, eventually leading to paralysis. About 40–50% of those left untreated can die. == Epidemiology ==
Epidemiology
for diphtheria per 100,000 inhabitants in 2004: between 1997 and 2006: Diphtheria is fatal in 5–10% of cases. In children under five years and adults over 40 years, the fatality rate may be as much as 20%. In 2013, it resulted in 3,300 deaths, down from 8,000 deaths in 1990. Better standards of living, mass immunization, improved diagnosis, prompt treatment, and more effective health care have led to a decrease in cases worldwide. ==History==
History
Discovery and science Records of Diphtheria begin as early as the 5th century BCE in the writings of Hippocrates. Epidemics were first described by Aëtius of Amida in the 6th century. In 1883, Edwin Klebs identified the bacterium causing diphtheria, and named it Klebs–Loeffler bacterium. The club shape of this bacterium helped Edwin to differentiate it from other bacteria. Over time, it has been called Microsporon diphtheriticum, Bacillus diphtheriae, and Mycobacterium diphtheriae. Current nomenclature is Corynebacterium diphtheriae. In 1884, German bacteriologist Friedrich Loeffler became the first person known to cultivate C. diphtheriae. Löffler found that the bacteria were always present in the mucous membranes of the larynx and trachea of patients with diphtheria. In the process of finding the bacteria, he isolated the organism, cultured it, and reproduced the disease in susceptible animals (guinea pigs and rabbits), and then recovered the same bacillus from the diseased animal, thus fulfilling Koch's postulates. He believed there was a toxin that was made by the bacteria that caused the disease symptoms, and subsequently showed that some animals are immune to diphtheria. In 1885, Joseph P. O'Dwyer introduced the O'Dwyer tube for laryngeal intubation in patients with an obstructed larynx. It soon replaced tracheostomy as the emergency diphtheric intubation method. In 1888, Emile Roux and Alexandre Yersin showed that a substance (exotoxin) produced by C. diphtheriae caused symptoms of diphtheria in animals. In 1890, Shibasaburō Kitasato and Emil von Behring immunized guinea pigs with heat-treated diphtheria toxin. They also immunized goats and horses in the same way, and showed that an "antitoxin" made from serum of immunized animals could cure the disease in non-immunized animals. Behring used this antitoxin (now known to consist of antibodies that neutralize the toxin produced by C. diphtheriae) for human trials in 1891, but they were unsuccessful. Successful treatment of human patients with horse-derived antitoxin began in 1894, after production and quantification of antitoxin had been optimized. In 1901, Von Behring won the first Nobel Prize in medicine for his work on diphtheria. In 1895, H. K. Mulford Company of Philadelphia started production and testing of diphtheria antitoxin in the United States. Park and Biggs described the method for producing serum from horses for use in diphtheria treatment. In 1897, Paul Ehrlich developed a standardized unit of measure for diphtheria antitoxin. This was the first ever standardization of a biological product, and played an important role in future developmental work on sera and vaccines. In 1901, 10 of 11 inoculated St. Louis children died from contaminated diphtheria antitoxin. The horse from which the antitoxin was derived died of tetanus. This incident, coupled with a tetanus outbreak in Camden, New Jersey, played an important part in initiating federal regulation of biologic products. In 1905, Franklin Royer, from Philadelphia's Municipal Hospital, published a paper urging timely treatment for diphtheria and adequate doses of antitoxin. In 1906, Clemens Pirquet and Béla Schick described serum sickness in children receiving large quantities of horse-derived antitoxin. Schick and Pirquet reported that children treated for diphtheria with very large doses of horse-derived antitoxin frequently developed delayed symptoms, including swelling, fever, rash, and joint pain. It is now understood that these reactions occur because the human immune system recognizes the foreign antibodies in horse serum as antigens, triggering a cascade of immune responses. In the clinical experience of Pirquet and Schick, these reactions were self-limited rather than life-threatening, and children who survived diphtheria were not permanently harmed by the antitoxin treatment. Between 1910 and 1911, Béla Schick developed the Schick test to detect pre-existing immunity to diphtheria in an exposed person. Only those who had not been exposed to diphtheria were vaccinated. A massive, five-year campaign was coordinated by Dr. Schick. As a part of the campaign, 85 million pieces of literature were distributed by the Metropolitan Life Insurance Company, with an appeal to parents to "Save your child from diphtheria." In 1914, William H. Park investigated the use of carefully calibrated mixtures of diphtheria toxin and antitoxin to induce active immunity in experimental animals and later humans. Building on earlier antitoxin work, he systematically adjusted the relative concentrations to identify formulations that produced durable protective immunity while minimizing adverse reactions to the toxin–antitoxin complex. This mixture, TAT (for toxin-antitoxin), became the first vaccine against diphtheria. In 1919, in Dallas, Texas, 10 children were killed and 60 others made seriously ill by toxic antitoxin, which had passed the tests of the New York State Health Department. The manufacturer of the antitoxin, the Mulford Company of Philadelphia, paid damages in every case. In 1926, Alexander Thomas Glenny increased the effectiveness of diphtheria toxoid (a modified version of the toxin used for vaccination) by treating it with aluminum salts. Vaccination with toxoid was not widely used until the early 1930s. In 1939, Dr. Nora Wattie, who was the Principal Medical Officer (Maternity and Child Welfare) of Glasgow between 1934– 1964, introduced immunisation clinics across Glasgow, and promoted mother and child health education, resulting in virtual eradication of the infection in the city. Widespread vaccination pushed cases in the United States down from 4.4 per 100,000 inhabitants in 1932 to 2.0 in 1937. In Nazi Germany, where authorities preferred treatment and isolation over vaccination (until about 1939–1941), cases rose over the same period from 6.1 to 9.6 per 100,000 inhabitants. List of epidemics • In 1613, Spain experienced an epidemic of diphtheria, referred to as (The Year of Strangulations). • In 1705, the Mariana Islands experienced an epidemic of diphtheria and typhus simultaneously, reducing the population to about 5,000 people. • In 1735, a diphtheria epidemic swept through New England. Then known as "throat distemper," in one New Hampshire town, 32% of children under 10 died. Of the persons known to have acquired diphtheria, nearly 40% died. Noah Webster wrote: "It was literally the plague among children. Many families lost three of four children—many lost all." • In 1856, Victor Fourgeaud described an epidemic of diphtheria in California. • In 1925, in Nome, Alaska; the "Great Race of Mercy" to deliver diphtheria antitoxin is now celebrated by the Iditarod Trail Sled Dog Race. During the 1920s, an annual estimate of 100,000 to 200,000 diphtheria cases and 13,000 to 15,000 deaths occurred in the United States. • In 1943, diphtheria outbreaks accompanied war and disruption in Europe. The 1 million cases in Europe resulted in 50,000 deaths. • During 1948 in Kyoto, 68 of 606 children died after diphtheria immunization due to improper manufacture of aluminum phosphate toxoid. • In 1974, the World Health Organization included DPT vaccine in their Expanded Programme on Immunization for developing countries. • In 1975, an outbreak of cutaneous diphtheria in Seattle, Washington, was reported. • After the breakup of the former Soviet Union in 1991, vaccination rates in its constituent countries fell so low that an explosion of diphtheria cases occurred. In 1991, 2,000 cases of diphtheria occurred in the USSR. Between 1991 and 1998, as many as 200,000 cases were reported in the Commonwealth of Independent States, resulting in 5,000 deaths. • In early May 2010, a case of diphtheria was diagnosed in Port-au-Prince, Haiti, after the devastating 2010 Haiti earthquake. The 15-year-old male patient died while workers searched for antitoxin. • In 2013, three children died of diphtheria in Hyderabad, India. • In early June 2015, a case of diphtheria was diagnosed at Vall d'Hebron University Hospital in Barcelona, Spain. The six-year-old child who died of the illness had not been previously vaccinated due to parental opposition to vaccination. It was the first case of diphtheria in the country since 1986, as reported by the Spanish daily newspaper El Mundo, or from 1998, as reported by the WHO. • In March 2016, a three-year-old girl died of diphtheria in the University Hospital of Antwerp, Belgium. • In June 2016, a three-year-old, five-year-old, and seven-year-old girl died of diphtheria in Kedah, Malacca, and Sabah, Malaysia. • In January 2017, more than 300 cases were recorded in Venezuela. • In 2017, outbreaks occurred in a Rohingya refugee camp in Bangladesh, and amongst children unvaccinated due to the Yemeni Civil War. • In November and December 2017, an outbreak of diphtheria occurred in Indonesia, with more than 600 cases found and 38 fatalities. • In November 2019, two cases of diphtheria occurred in the Lothian area of Scotland. Additionally, in November 2019, an unvaccinated eight-year-old boy died of diphtheria in Athens, Greece. • In July 2022, two cases of diphtheria occurred in northern New South Wales, Australia. • In October 2022, there was an outbreak of diphtheria at the former Manston airfield, a former Ministry of Defence (MoD) site in Kent, England, which had been converted to an asylum seeker processing centre. The capacity of the processing centre was 1,000 people, although about 3,000 were living at the site, with some accommodated in tents. The Home Office, the government department responsible for asylum seekers, refused to confirm the number of cases. • In December 2023, there was an outbreak at a school in Luton, in the United Kingdom. UK Health Security Agency (UKHSA) issued a statement saying specialists have been providing public health support following confirmation of the diphtheria case at a primary school in Luton. The agency said it is working closely with local and national partners "to ensure all necessary public health measures are implemented" following the discovery of the new case. The statement added: "We have conducted a risk assessment and close contacts of the case have been identified, and where appropriate, vaccination and advice will be given to prevent the spread of the infection." Notable deaths On April 8, 1861, Elisha Graves Otis died from diphtheria at age 49. In December 1863, Eliza Arabella Garfield, the eldest daughter of James A. Garfield, died from diphtheria at the age of three, right before Christmas. In 1878, Princess Alice (Queen Victoria's second daughter) and her family became infected with diphtheria; Princess Alice and her four-year-old daughter, Princess Marie, both died. Their deaths caused the Sanitary Journal to warn readers of the “kiss of death” that may have spread the disease through the royal family. On December 7, 1892, Eleanor Roosevelt's mother, Anna Hall Roosevelt, died of diphtheria at age 29. Five months later, Elliott Roosevelt Jr., Eleanor's younger brother, died of the disease. On January 7, 1904, Ruth Cleveland died of diphtheria at age 12 in Princeton, New Jersey. She was the eldest daughter of former President Grover Cleveland and the former First Lady, Frances Folsom. ==References==
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