Typhoid fever, also known as typhoid, is a disease caused by Salmonella serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several days. This is commonly accompanied by weakness, abdominal pain, constipation, headaches, and mild vomiting. Some people develop a skin rash with rose colored spots. In severe cases, people may experience confusion. Without treatment, symptoms may last weeks or months. Diarrhea may be severe, but is uncommon. Other people may carry it without being affected, but are still contagious. Typhoid fever is a type of enteric fever, along with paratyphoid fever. S. enterica Typhi is believed to infect and replicate only within humans.
Salmonella is a genus of rod-shaped (bacillus) gram-negative bacteria of the family Enterobacteriaceae. The two known species of Salmonella are Salmonella enterica and Salmonella bongori. S. enterica is the type species and is further divided into six subspecies that include over 2,600 serotypes. Salmonella was named after Daniel Elmer Salmon (1850–1914), an American veterinary surgeon.
Salmonella enterica is a rod-shaped, flagellate, facultative anaerobic, Gram-negative bacterium and a species of the genus Salmonella. It is divided into six subspecies, arizonae (IIIa), diarizonae (IIIb), houtenae (IV), salamae (II), indica (VI), and enterica (I). A number of its serovars are serious human pathogens; many of them are serovars of Salmonella enterica subsp. enterica.
A conjugate vaccine is a type of subunit vaccine which combines a weak antigen with a strong antigen as a carrier so that the immune system has a stronger response to the weak antigen.
The bacterial capsule is a large structure common to many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washed off, and it can be the cause of various diseases.
Pneumococcal polysaccharide vaccine, sold under the brand name Pneumovax 23, is a pneumococcal vaccine that is used for the prevention of pneumococcal disease caused by the 23 serotypes of Streptococcus pneumoniae contained in the vaccine as capsular polysaccharides. It is given by intramuscular or subcutaneous injection.
Paratyphoid fever, also known simply as paratyphoid, is a bacterial infection caused by one of three types of Salmonella enterica. Symptoms usually begin 6–30 days after exposure and are the same as those of typhoid fever. Often, a gradual onset of a high fever occurs 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, they are still able to spread the disease to others. Typhoid and paratyphoid are of similar severity. Paratyphoid and typhoid fever are types of enteric fever.
Hepatitis A vaccine is a vaccine that prevents hepatitis A. It is effective in around 95% of cases and lasts for at least twenty years and possibly a person's entire life. If given, two doses are recommended beginning after the age of one. It is given by injection into a muscle. The first hepatitis A vaccine was approved in Europe in 1991, and the United States in 1995. It is on the World Health Organization's List of Essential Medicines.
The Haemophilus influenzae type B vaccine, also known as Hib vaccine, is a vaccine used to prevent Haemophilus influenzae type b (Hib) infection. In countries that include it as a routine vaccine, rates of severe Hib infections have decreased more than 90%. It has therefore resulted in a decrease in the rate of meningitis, pneumonia, and epiglottitis.
Ty21a is a live attenuated bacterial vaccine that protects against typhoid. First licensed in Europe in 1983 and in the United States in 1989, it is an orally administered, live-attenuated Ty2 strain of S. Typhi in which multiple genes, including the genes responsible for the production of Vi, have been deleted so as to render it harmless but nevertheless immunogenic. It is one of the three typhoid vaccines currently recommended by the World Health Organization.
Arthur Felix, FRS was a Polish-born microbiologist and serologist.
NmVac4-A/C/Y/W-135 is the commercial name of the polysaccharide vaccine against the bacterium that causes meningococcal meningitis. The product, by JN-International Medical Corporation, is designed and formulated to be used in developing countries for protecting populations during meningitis disease epidemics.
Meningococcal vaccine refers to any vaccine used to prevent infection by Neisseria meningitidis. Different versions are effective against some or all of the following types of meningococcus: A, B, C, W-135, and Y. The vaccines are between 85 and 100% effective for at least two years. They result in a decrease in meningitis and sepsis among populations where they are widely used. They are given either by injection into a muscle or just under the skin.
Typhoid vaccines are vaccines that prevent typhoid fever. Several types are widely available: typhoid conjugate vaccine (TCV), Ty21a and Vi capsular polysaccharide vaccine (ViPS). They are about 30 to 70% effective in the first two years, depending on the specific vaccine in question. The Vi-rEPA vaccine has been shown to be efficacious in children.
A subunit vaccine is a vaccine that contains purified parts of the pathogen that are antigenic, or necessary to elicit a protective immune response. Subunit vaccine can be made from dissembled viral particles in cell culture or recombinant DNA expression, in which case it is a recombinant subunit vaccine.
Salmonella enterica subsp. enterica is a subspecies of Salmonella enterica, the rod-shaped, flagellated, aerobic, Gram-negative bacterium. Many of the pathogenic serovars of the S. enterica species are in this subspecies, including that responsible for typhoid.
Edward Thomas Ryan is an American microbiologist, immunologist, and physician at Harvard University and Massachusetts General Hospital. Ryan served as president of the American Society of Tropical Medicine and Hygiene from 2009 to 2010. Ryan is Professor of Immunology and Infectious Diseases at the Harvard T.H. Chan School of Public Health, Professor of Medicine at Harvard Medical School, and Director of Global Infectious Diseases at the Massachusetts General Hospital. Ryan's research and clinical focus has been on infectious diseases associated with residing in, immigrating from, or traveling through resource-limited areas. Ryan is a Fellow of the American Society of Microbiology, the American Society of Tropical Medicine and Hygiene, the American College of Physicians, and the Infectious Diseases Society of America.
Hepatitis A and typhoid vaccine is a combination vaccine to protect against the infectious diseases hepatitis A and typhoid. It is a combination of inactivated Hepatitis A virus and Vi polysaccharide of Salmonella typhi bacteria. Branded formulations include Hepatyrix from GlaxoSmithKline, and ViVaxim and ViATIM from Sanofi Pasteur.
In 2000, typhoid fever caused an estimated 21.7 million illnesses and 217,000 deaths. It occurs most often in children and young adults between 5 and 19 years old. In 2013, it resulted in about 161,000 deaths – down from 181,000 in 1990. Infants, children, and adolescents in south-central and Southeast Asia experience the greatest burden of illness. Outbreaks of typhoid fever are also frequently reported from sub-Saharan Africa and countries in Southeast Asia. In the United States, about 400 cases occur each year, and 75% of these are acquired while traveling internationally.
Melita Alison Gordon is a gastroenterologist who works on invasive gut pathogens and tropical gastrointestinal disease. She leads the Malawi Liverpool Wellcome Trust Salmonella and Enterics Group. Gordon was awarded the British Society of Gastroenterology Sir Francis Avery Jones Research Medal in 2011.
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