medical_specialty viral hepatitis
Hepatitis D ( hepatitis delta ) is a disease caused by the " hepatitis D virus " (" HDV "), a small spherical enveloped RNA virus . This is one of five known hepatitis viruses : A , B , C , D , and E . HDV is considered to be a subviral satellite because it can propagate only in the presence of the hepatitis B virus ( HBV ). Transmission of HDV can occur either via simultaneous ___MASK18___ with HBV ( coinfection ) or superimposed on chronic hepatitis B or hepatitis B carrier state ( superinfection ). Childbirth , also known as labour and delivery , is the ending of a pregnancy by one or more babies leaving a woman ' s uterus . In 2015 there were about 135 million births globally . About 15 million were born before 37 weeks of gestation , while between 3 and 12 % were born after 42 weeks . In the developed world most deliveries occur in hospital , while in the developing world most births take place at home with the support of a traditional birth attendant . The most common way of childbirth is a vaginal delivery . It involves three stages of labour : the shortening and opening of the cervix , descent and birth of the baby , and the pushing out of the placenta . The first stage typically lasts twelve to nineteen hours , the second stage twenty minutes to two hours , and the third stage five to thirty minutes . The first stage begins with crampy abdominal or back pains that last around half a minute and occur every ten to thirty minutes . The crampy pains become stronger and closer together over time . During the second stage pushing with contractions may occur . In the third stage delayed clamping of the umbilical cord is generally recommended . A number of methods can help with pain such as relaxation techniques , opioids , and spinal blocks . Most babies are born head first ; however about 4 % are born feet or buttock first , known as breech . During labour a woman can generally eat and move around as she likes , but pushing is not recommended during the first stage or during delivery of the head , and enemas are not recommended . While making a cut to the opening of the vagina is common , known as an episiotomy , it is generally not needed . In 2012 , about 23 million deliveries occurred by a surgical procedure known as Caesarean section . Caesarean sections may be recommended for twins , signs of distress in the baby , or breech position . This method of delivery can take longer to heal from . Each year complications from pregnancy and childbirth result in about 500 , 000 maternal deaths , 7 million women have serious long term problems , and 50 million women have health negative outcomes following delivery . Most of these occur in the developing world . Specific complications include obstructed labour , postpartum bleeding , eclampsia , and postpartum ___MASK18___ . Complications in the baby include birth asphyxia . Betaherpesvirinae is a subfamily of viruses in the order Herpesvirales , in the family Herpesviridae . Mammals serve as natural hosts . There are currently 18 species in this subfamily , divided among 4 genera . Diseases associated with this subfamily include : HHV - 5 : congenital CMV ___MASK18___ . HHV - 6 : ' sixth disease ' ( roseola infantum , exanthem subitum ). HHV - 7 : symptoms analog to the ' sixth disease '. Vaccination is the administration of antigenic material ( a vaccine ) to stimulate an individual ' s immune system to develop adaptive immunity to a pathogen . Vaccines can prevent or ameliorate morbidity from ___MASK18___ . When a sufficiently large percentage of a population has been vaccinated , this results in herd immunity . The effectiveness of vaccination has been widely studied and verified ; for example , the influenza vaccine , the HPV vaccine , and the chicken pox vaccine . Vaccination is the most effective method of preventing infectious diseases ; widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the restriction of diseases such as polio , measles , and tetanus from much of the world . The World Health Organization ( WHO ) reports that licensed vaccines are currently available to prevent or contribute to the prevention and control of twenty - five preventable infections . Liver cancer , also known as hepatic cancer and primary hepatic cancer , is cancer that starts in the liver . Cancer which has spread from elsewhere to the liver , known as liver metastasis , is more common than that which starts in the liver . Symptoms of liver cancer may include a lump or pain in the right side below the rib cage . Other symptoms includes swelling of the abdomen , yellowish skin , easy bruising , weight loss , and weakness . The leading cause of liver cancer is cirrhosis due to either hepatitis B , hepatitis C , or alcohol . Other causes include aflatoxin , non - alcoholic fatty liver disease , and liver flukes . The most common types are hepatocellular carcinoma ( HCC ) which makes up 80 % of cases and cholangiocarcinoma . Less common types include mucinous cystic neoplasm and intraductal papillary biliary neoplasm . The diagnosis may be supported by blood tests and medical imaging with confirmation by tissue biopsy . Preventive efforts include immunization against hepatitis B and treating those infected with hepatitis B or C . Screening is recommended in those with chronic liver disease . Treatment options may include ___MASK56___ , targeted therapy , and radiation therapy . In certain cases ablation therapy , embolization therapy , or liver transplantation may be used . Small lumps in the liver may be simply closely followed . Primary liver cancer is globally the sixth most frequent cancer ( 6 %) and the second leading cause of death from cancer ( 9 %). In 2012 it occurred in 782 , 000 people and resulted in 746 , 000 deaths . In 2013 , 300 , 000 deaths from liver cancer were due to hepatitis B , 343 , 000 to hepatitis C , and 92 , 000 to alcohol . Higher rates of liver cancer occur where hepatitis B and C are common , including Asia and sub - Saharan Africa . Males are more often affected with HCC than females . Diagnosis is most frequent among those 55 to 65 years old . Five - year survival rates are 18 % in the United States . The word " hepatic " is from the Greek " hêpar ", meaning " liver ". Classification . The most frequent liver cancer , accounting for approximately 75 % of all primary liver cancers , is hepatocellular carcinoma ( HCC ) ( also named " hepatoma ", which is a misnomer because adenomas are usually benign ). HCC is a cancer formed by liver cells , known as hepatocytes , that become malignant . Another type of cancer formed by liver cells is hepatoblastoma , which is specifically formed by immature liver cells .< ref name =" doi10 . 1016 / j . mpsur . 2008 . 12 . 005 "></ ref > It is a rare malignant tumor that primarily develops in children , and accounts for approximately 1 % of all cancers in children and 79 % of all primary liver cancers under the age of 15 . Most hepatoblastomas form in the right lobe . Pneumonia is an inflammatory condition of the lung affecting primarily the microscopic air sacs known as alveoli . Typical signs and symptoms include a varying severity and combination of productive or dry cough , chest pain , fever , and trouble breathing , depending on the underlying cause . Pneumonia is usually caused by ___MASK18___ with viruses or bacteria and less commonly by other microorganisms , certain medications and conditions such as autoimmune diseases . Risk factors include other lung diseases such as cystic fibrosis , COPD , and asthma , diabetes , heart failure , a history of smoking , a poor ability to cough such as following a stroke , or a weak immune system . Diagnosis is often based on the symptoms and physical examination . Chest X - ray , blood tests , and culture of the sputum may help confirm the diagnosis . The disease may be classified by where it was acquired with community , hospital , or health care associated pneumonia . Vaccines to prevent certain types of pneumonia are available . Other methods of prevention include handwashing and not smoking . Treatment depends on the underlying cause . Pneumonia believed to be due to bacteria is treated with antibiotics . If the pneumonia is severe , the affected person is generally hospitalized . Oxygen therapy may be used if oxygen levels are low . Pneumonia affects approximately 450 million people globally ( 7 % of the population ) and results in about 4 million deaths per year . Pneumonia was regarded by William Osler in the 19th century as " the captain of the men of death ". With the introduction of antibiotics and vaccines in the 20th century , survival improved . Nevertheless , in developing countries , and among the very old , the very young , and the chronically ill , pneumonia remains a leading cause of death . Pneumonia often shortens suffering among those already close to death and has thus been called " the old man ' s friend ". Herpes simplex (" herps ", " creeping " or " latent ") is a viral disease caused by the herpes simplex virus . Infections are categorized based on the part of the body infected . Oral herpes involves the face or mouth . It may result in small blisters in groups often called cold sores or fever blisters or may just cause a sore throat . Genital herpes , often simply known as herpes , may have minimal symptoms or form blisters that break open and result in small ulcers . These typically heal over two to four weeks . Tingling or shooting pains may occur before the blisters appear . Herpes cycles between periods of active disease followed by periods without symptoms . The first episode is often more severe and may be associated with fever , muscle pains , swollen lymph nodes and headaches . Over time , episodes of active disease decrease in frequency and severity . Other disorders caused by herpes simplex include : herpetic whitlow when it involves the fingers , herpes of the eye , herpes ___MASK18___ of the brain , and neonatal herpes when it affects a newborn , among others . There are two types of herpes simplex virus , type 1 ( HSV - 1 ) and type 2 ( HSV - 2 ). HSV - 1 more commonly causes oral infections while HSV - 2 more commonly causes genital infections . They are transmitted by direct contact with body fluids or lesions of an infected individual . Transmission may still occur when symptoms are not present . Genital herpes is classified as a sexually transmitted ___MASK18___ . It may be spread to an infant during childbirth . After ___MASK18___ , the viruses are transported along sensory nerves to the nerve cell bodies , where they reside lifelong . Causes of recurrence may include : decreased immune function , stress , and sunlight exposure . Oral and genital herpes is usually diagnosed based on the presenting symptoms . The diagnosis may be confirmed by viral culture or detecting herpes DNA in fluid from blisters . Testing the blood for antibodies against the virus can confirm a previous ___MASK18___ but will be negative in new infections . The most effective method of avoiding genital infections is by avoiding vaginal , oral , and anal sex . Condom use decreases the risk somewhat . Daily antiviral medication taken by someone who has the ___MASK18___ can also reduce spread . There is no available vaccine and once infected , there is no cure . Paracetamol ( acetaminophen ) and topical lidocaine may be used to help with the symptoms . Treatments with antiviral medication such as aciclovir or valaciclovir can lessen the severity of symptomatic episodes . Worldwide rates of either HSV - 1 or HSV - 2 are between 60 % and 95 % in adults . HSV - 1 is usually acquired during childhood . Rates of both increase as people age . Rates of HSV - 1 are between 70 % and 80 % in populations of low socioeconomic status and 40 % to 60 % in populations of improved socioeconomic status . An estimated 536 million people worldwide ( 16 % of the population ) were infected with HSV - 2 as of 2003 with greater rates among women and those in the developing world . Most people with HSV - 2 do not realize that they are infected . Viral hepatitis is liver inflammation due to a viral ___MASK18___ . It may present in acute ( recent ___MASK18___ , relatively rapid onset ) or chronic forms . The most common causes of viral hepatitis are the five unrelated hepatotropic viruses Hepatitis A , Hepatitis B , Hepatitis C , Hepatitis D , and Hepatitis E . In addition to the nominal hepatitis viruses , other viruses that can also cause liver inflammation include Herpes simplex , Cytomegalovirus , Epstein -- Barr virus , and Yellow fever . Medical literature is the scientific literature of medicine : articles in journals and texts in books devoted to the field of medicine . Many references to the medical literature include the health care literature generally , including that of ___MASK96___ , veterinary medicine , pharmacy , nursing , and the allied health professions . A blister is a small pocket of lymph within the upper layers of the skin , typically caused by forceful rubbing ( friction ), burning , freezing , chemical exposure or ___MASK18___ . Most blisters are filled with a clear fluid , either serum or plasma . However , blisters can be filled with blood ( known as blood blisters ) or with pus ( if they become infected ). A viral disease ( or viral ___MASK18___ ) occurs when an organism ' s body is invaded by pathogenic viruses , and infectious virus particles ( virions ) attach to and enter susceptible cells . Hepatitis C is an ___MASK6___ caused by the hepatitis C virus ( HCV ) that primarily affects the liver . During the initial infection people often have mild or no symptoms . Occasionally a fever , dark urine , abdominal pain , and yellow tinged skin occurs . The virus persists in the liver in about 75 % to 85 % of those initially infected . Early on chronic infection typically has no symptoms . Over many years however , it often leads to liver disease and occasionally cirrhosis . In some cases , those with cirrhosis will develop complications such as liver failure , liver cancer , or esophageal and gastric varices . HCV is spread primarily by blood - to - blood contact associated with intravenous drug use , poorly sterilized medical equipment , needlestick injuries in healthcare , and transfusions . Using blood screening , the risk from a transfusion is less than one per two million . It may also be spread from an infected mother to her baby during birth . It is not spread by superficial contact . It is one of five known hepatitis viruses : A , B , C , D , and E . Diagnosis is by blood testing to look for either antibodies to the virus or its RNA . Testing is recommended in all people who are at risk . There is no vaccine against hepatitis C . Prevention includes harm reduction efforts among people who use intravenous drugs and testing donated blood . Chronic infection can be cured about 90 % of the time with treatments that include the medications sofosbuvir or simeprevir . Previous to this a combination of peginterferon and ribavirin was used which had a cure rate around 50 % and greater side effects . Getting access to the newer treatments however can be expensive . Those who develop cirrhosis or liver cancer may require a liver transplant . Hepatitis C is the leading reason for liver transplantation , though the virus usually recurs after transplantation . An estimated 130  200 million people worldwide are infected with hepatitis C . In 2013 about 11 million new cases occurred . It occurs most commonly in Africa and Central and East Asia . About 343 , 000 deaths due to liver cancer and 358 , 000 deaths due to cirrhosis occurred in 2013 due to hepatitis C . The existence of hepatitis C  originally identifiable only as a type of non - A non - B hepatitis  was suggested in the 1970s and proven in 1989 . Hepatitis C infects only humans and chimpanzees . Jaundice , also known as icterus , is a yellowish or greenish pigmentation of the skin and whites of the eyes due to high bilirubin levels . It is commonly associated with itchiness . The feces may be pale and the urine dark . Jaundice in babies occurs in over half in the first week following birth and in most is not a problem . If bilirubin levels in babies are very high for too long a type of brain damage , known as kernicterus , may occur . Causes of jaundice vary from non - serious to potentially fatal . Levels of bilirubin in blood are normally below 1 . 0 mg / dL ( 17 µmol / L ) and levels over 2 - 3 mg / dL ( 34 - 51 µmol / L ) typically results in jaundice . High bilirubin is divided into two types : unconjugated ( indirect ) and conjugated ( direct ). Conjugated bilirubin can be confirmed by finding bilirubin in the urine . Other conditions that can cause yellowish skin but are not jaundice include carotenemia from eating large amounts of certain foods and medications like rifampin . High unconjugated bilirubin may be due to excess red blood cell breakdown , large bruises , genetic conditions such as Gilbert ' s syndrome , no eating for a prolonged period of time , newborn jaundice , or thyroid problems . High conjugated bilirubin may be due to liver diseases such as cirrhosis or hepatitis , infections , medications , or blockage of the bile duct . In the developed world the cause is more often blockage of the bile duct or medications while in the developing world it is more often infections such as viral hepatitis , leptospirosis , schistosomiasis , or malaria . Blockage of the bile duct may occur due to gallstones , cancer , or pancreatitis . Medical imaging such as ultrasound is useful for detecting bile duct blockage . Treatment of jaundice is typically determined by the underlying cause . If a bile duct blockage is present ___MASK56___ is typically required , otherwise management is medical . Medical management may involve treating infectious causes and stopping medication that could be contributing . Among newborns , depending on age and prematurity , a bilirubin greater than 4 - 21 mg / dL ( 68 - 360 µmol / L ) may be treated with phototherapy or exchanged transfusion . The itchiness may be helped by draining the gallbladder or ursodeoxycholic acid . The word " jaundice " is from the French " jaunisse ", meaning " yellow disease ". Hepatitis A ( formerly known as infectious hepatitis ) is an ___MASK6___ of the liver caused by the hepatitis A virus ( HAV ). Many cases have few or no symptoms , especially in the young . The time between infection and symptoms , in those who develop them , is between two and six weeks . When symptoms occur , they typically last eight weeks and may include nausea , vomiting , diarrhea , jaundice , fever , and abdominal pain . Around 10  15 % of people experience a recurrence of symptoms during the six months after the initial infection . Acute liver failure may rarely occur , with this being more common in the elderly . It is usually spread by eating food or drinking water contaminated with infected feces . Shellfish which have not been sufficiently cooked are a relatively common source . It may also be spread through close contact with an infectious person . While children often do not have symptoms when infected , they are still able to infect others . After a single infection , a person is immune for the rest of his or her life . Diagnosis requires blood testing , as the symptoms are similar to those of a number of other diseases . It is one of five known hepatitis viruses : A , B , C , D , and E . The hepatitis A vaccine is effective for prevention . Some countries recommend it routinely for children and those at higher risk who have not previously been vaccinated . It appears to be effective for life . Other preventive measures include hand washing and properly cooking food . No specific treatment is available , with rest and medications for nausea or diarrhea recommended on an as - needed basis . Infections usually resolve completely and without ongoing liver disease . Treatment of acute liver failure , if it occurs , is with liver transplantation . Globally , around 1 . 4 million symptomatic cases occur each year and about 102 million infections ( symptomatic and asymptomatic ). It is more common in regions of the world with poor sanitation and not enough safe water . In the developing world about 90 % of children have been infected by age 10 and thus are immune by adulthood . It often occurs in outbreaks in moderately developed countries where children are not exposed when young and vaccination is not widespread . Acute hepatitis A resulted in 102 , 000 deaths in 2010 . World Hepatitis Day occurs each year on July 28 to bring awareness to viral hepatitis . A superinfection is generally defined as a second ___MASK18___ superimposed on an earlier one , especially by a different microbial agent of exogenous or endogenous origin , that is resistant to the treatment being used against the first ___MASK18___ . Examples of this in bacteriology are the overgrowth of endogenous " Clostridium difficile " which occurs following treatment with a broad - spectrum antibiotic , and pneumonia or septicemia from " Pseudomonas aeruginosa " in some immuno - compromised patients . In parasitology , coinfection is the simultaneous ___MASK18___ of a host by multiple pathogen species . In virology , coinfection includes simultaneous ___MASK18___ of a single cell by two or more virus particles . An example is the coinfection of liver cells with Hepatitis B virus and Hepatitis D virus , which can arise incrementally by initial ___MASK18___ followed by superinfection . Cytomegalovirus ( CMV ) ( from the Greek " cyto -", " cell ", and " megalo -", " large ") is a genus of viruses in the order Herpesvirales , in the family Herpesviridae , in the subfamily Betaherpesvirinae . Humans and monkeys serve as natural hosts . There are currently eight species in this genus including the type species , human cytomegalovirus ( HCMV , human herpesvirus 5 , HHV - 5 ), which is the species that infects humans . Diseases associated with HHV - 5 include glandular fever , and pneumonia . In the medical literature , most mentions of CMV without further specification refer implicitly to human CMV . Human CMV is the most studied of all cytomegaloviruses . ___MASK18___ is the invasion of an organism ' s body tissues by disease - causing agents , their multiplication , and the reaction of host tissues to these organisms and the toxins they produce . ___MASK6___ , also known as transmissible disease or communicable disease , is illness resulting from an infection . Infections are caused by infectious agents including viruses , viroids , prions , bacteria , nematodes such as parasitic roundworms and pinworms , arthropods such as ticks , mites , fleas , and lice , fungi such as ringworm , and other macroparasites such as tapeworms and other helminths . Hepatitis B is an ___MASK6___ caused by the hepatitis B virus ( HBV ) which 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 240 million to 350 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 . Signs and symptoms . 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 . A herpetic whitlow is a lesion ( whitlow ) on a finger or thumb caused by the herpes simplex virus . It is a painful ___MASK18___ that typically affects the fingers or thumbs . Occasionally ___MASK18___ occurs on the toes or on the nail cuticle . Herpes whitlow can be caused by ___MASK18___ by HSV - 1 or HSV - 2 . HSV - 1 whitlow is often contracted by health care workers that come in contact with the virus ; it is most commonly contracted by dental workers and medical workers exposed to oral secretions . It is also often observed in thumb - sucking children with primary HSV - 1 oral ___MASK18___ ( autoinoculation ) prior to seroconversion , and in adults aged 20 to 30 following contact with HSV - 2 - infected genitals . Symptoms of herpetic whitlow include swelling , reddening and tenderness of the skin of infected finger . This may be accompanied by fever and swollen lymph nodes . Small , clear vesicles initially form individually , then merge and become cloudy . Associated pain often seems large relative to the physical symptoms . The herpes whitlow lesion usually heals in two to three weeks . It may reside in axillary sensory ganglia to cause recurrent herpetic lesions on that arm or digits . Diarrhea , also spelled diarrhoea , is the condition of having at least three loose or liquid bowel movements each day . It often lasts for a few days and can result in dehydration due to fluid loss . Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behaviour . This can progress to decreased urination , loss of skin color , a fast heart rate , and a decrease in responsiveness as it becomes more severe . Loose but non - watery stools in babies who are breastfed , however , may be normal . The most common cause is an ___MASK18___ of the intestines due to either a virus , bacteria , or parasite ; a condition known as gastroenteritis . These infections are often acquired from food or water that has been contaminated by stool , or directly from another person who is infected . It may be divided into three types : short duration watery diarrhea , short duration bloody diarrhea , and if it lasts for more than two weeks , persistent diarrhea . The short duration watery diarrhea may be due to an ___MASK18___ by cholera , although this is rare in the developed world . If blood is present it is also known as dysentery . A number of non - infectious causes may also result in diarrhea , including hyperthyroidism , lactose intolerance , inflammatory bowel disease , a number of medications , and irritable bowel syndrome . In most cases , stool cultures are not required to confirm the exact cause . Prevention of infectious diarrhea is by improved sanitation , clean drinking water , and hand washing with soap . Breastfeeding for at least six months is also recommended as is vaccination against rotavirus . Oral rehydration solution ( ORS ), which is clean water with modest amounts of salts and sugar , is the treatment of choice . Zinc tablets are also recommended . These treatments have been estimated to have saved 50 million children in the past 25 years . When people have diarrhea it is recommended that they continue to eat healthy food and babies continue to be breastfed . If commercial ORS are not available , homemade solutions may be used . In those with severe dehydration , intravenous fluids may be required . Most cases ; however , can be managed well with fluids by mouth . Antibiotics , while rarely used , may be recommended in a few cases such as those who have bloody diarrhea and a high fever , those with severe diarrhea following travelling , and those who grow specific bacteria or parasites in their stool . Loperamide may help decrease the number of bowel movements but is not recommended in those with severe disease . About 1 . 7 to 5 billion cases of diarrhea occur per year . It is most common in developing countries , where young children get diarrhea on average three times a year . Total deaths from diarrhea are estimated at 1 . 26 million in 2013  down from 2 . 58 million in 1990 . In 2012 , it was the second most common cause of deaths in children younger than five ( 0 . 76 million or 11 %). Frequent episodes of diarrhea are also a common cause of malnutrition and the most common cause in those younger than five years of age . Other long term problems that can result include stunted growth and poor intellectual development . Yellow fever is an acute viral disease . In most cases , symptoms include fever , chills , loss of appetite , nausea , muscle pains particularly in the back , and headaches . Symptoms typically improve within five days . In some people within a day of improving , the fever comes back , abdominal pain occurs , and liver damage begins causing yellow skin . If this occurs , the risk of bleeding and kidney problems is also increased . The disease is caused by the yellow fever virus and is spread by the bite of an infected female mosquito . It infects only humans , other primates , and several species of mosquitoes . In cities , it is spread primarily by mosquitoes of the " Aedes aegypti " type . The virus is an RNA virus of the genus " Flavivirus ". The disease may be difficult to tell apart from other illnesses , especially in the early stages . To confirm a suspected case , blood sample testing with polymerase chain reaction is required . A safe and effective vaccine against yellow fever exists and some countries require vaccinations for travelers . Other efforts to prevent ___MASK18___ include reducing the population of the transmitting mosquito . In areas where yellow fever is common and vaccination is uncommon , early diagnosis of cases and immunization of large parts of the population is important to prevent outbreaks . Once infected , management is symptomatic with no specific measures effective against the virus . The second and more severe phase results in death in up to half of people without treatment . Yellow fever causes 200 , 000 infections and 30 , 000 deaths every year , with nearly 90 % of these occurring in Africa . Nearly a billion people live in an area of the world where the disease is common . It is common in tropical areas of South America and Africa , but not in Asia . Since the 1980s , the number of cases of yellow fever has been increasing . This is believed to be due to fewer people being immune , more people living in cities , people moving frequently , and changing climate . The disease originated in Africa , from where it spread to South America through the slave trade in the 17th century . Since the 17th century , several major outbreaks of the disease have occurred in the Americas , Africa , and Europe . In the 18th and 19th centuries , yellow fever was seen as one of the most dangerous infectious diseases . In 1927 yellow fever virus became the first human virus to be isolated . Hepatitis is inflammation of the liver . Some people have no symptoms whereas others develop yellow discoloration of the skin and whites of the eyes , poor appetite , vomiting , tiredness , abdominal pain , or diarrhea . Hepatitis may be temporary ( acute ) or long term ( chronic ) depending on whether it lasts for less than or more than six months . Acute hepatitis can sometimes resolve on its own , progress to chronic hepatitis , or rarely result in acute liver failure . Over time the chronic form may progress to scarring of the liver , liver failure , or liver cancer . The most common cause worldwide is viruses . Other causes include heavy alcohol use , certain medications , toxins , other infections , autoimmune diseases , and non - alcoholic steatohepatitis ( NASH ). There are five main types of viral hepatitis : type A , B , C , D , and E . Hepatitis A and E are mainly spread by contaminated food and water . Hepatitis B is mainly sexually transmitted , but may also be passed from mother to baby during pregnancy or childbirth . Both hepatitis B and hepatitis C are commonly spread through infected blood such as may occur during needle sharing by intravenous drug users . Hepatitis D can only infect people already infected with hepatitis B . Hepatitis A , B , and D are preventable with immunization . Medications may be used to treat chronic cases of viral hepatitis . There is no specific treatment for NASH ; however , a healthy lifestyle , including physical activity , a healthy diet , and weight loss , is important . Autoimmune hepatitis may be treated with medications to suppress the immune system . A liver transplant may also be an option in certain cases . Worldwide in 2015 , hepatitis A occurred in about 114 million people , chronic hepatitis B affected about 343 million people and chronic hepatitis C about 142 million people . In the United States , NASH affects about 11 million people and alcoholic hepatitis affects about 5 million people . Hepatitis results in more than a million deaths a year , most of which occur indirectly from liver scarring or liver cancer . In the United States , hepatitis A is estimated to occur in about 2 , 500 people a year and results in about 75 deaths . The word is derived from the Greek " hêpar ", meaning " liver ", and "- itis ", meaning " inflammation ". Hepatitis E is a viral hepatitis ( liver inflammation ) caused by ___MASK18___ with a virus called hepatitis E virus . It is one of five known human hepatitis viruses : A , B , C , D , and E . HEV is a positive - sense single - stranded non - enveloped RNA icosahedral virus , HEV has a fecal - oral transmission route . ___MASK18___ with this virus was first documented in 1955 during an outbreak in New Delhi , India . A preventative vaccine ( HEV 239 ) is approved for use in China . A disease is a particular abnormal condition , a disorder of a structure or function , that affects part or all of an organism . The study of disease is called ___MASK64___ which includes the causal study of etiology . Disease is often construed as a medical condition associated with specific symptoms and signs . It may be caused by external factors such as pathogens , or it may be caused by internal dysfunctions particularly of the immune system such as an immunodeficiency , or a hypersensitivity including allergies and autoimmunity . A vaccine is a biological preparation that provides active acquired immunity to a particular disease . A vaccine typically contains an agent that resembles a disease - causing microorganism and is often made from weakened or killed forms of the microbe , its toxins or one of its surface proteins . The agent stimulates the body ' s immune system to recognize the agent as a threat , destroy it , and keep a record of it so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters . Vaccines can be prophylactic ( example : to prevent or ameliorate the effects of a future ___MASK18___ by any natural or " wild " pathogen ), or therapeutic ( e . g ., vaccines against cancer are being investigated ). Sexually transmitted infections ( STI ), also referred to as sexually transmitted diseases ( STD ) and venereal diseases ( VD ), are infections that are commonly spread by sex , especially vaginal intercourse , anal sex and oral sex . Most STIs initially do not cause symptoms . This results in a greater risk of passing the disease on to others . Symptoms and signs of disease may include vaginal discharge , penile discharge , ulcers on or around the genitals , and pelvic pain . STIs acquired before or during birth may result in poor outcomes for the baby . Some STIs may cause problems with the ability to get pregnant . More than 30 different bacteria , viruses , and parasites can cause STIs . Bacterial STIs include chlamydia , gonorrhea , and syphilis among others . Viral STIs include genital herpes , HIV / AIDS , and genital warts among others . Parasitic STIs include trichomoniasis among others . While usually spread by sex , some STIs can also be spread by non - sexual contact with contaminated blood and tissues , breastfeeding , or during childbirth . STI diagnostic tests are easily available in the developed world , but this is often not the case in the developing world . The most effective way of preventing STIs is by not having sex . Some vaccinations may also decrease the risk of certain infections including hepatitis B and some types of HPV . Safer sex practices such as use of condoms , having a smaller number of sexual partners , and being in a relationship where each person only has sex with the other also decreases the risk . Circumcision in males may be effective to prevent some infections . Most STIs are treatable or curable . Of the most common infections , syphilis , gonorrhea , chlamydia , trichomoniasis are curable , while herpes , hepatitis B , HIV / AIDS , and HPV are treatable but not curable . Resistance to certain antibiotics is developing among some organisms such as gonorrhea . In 2008 , it was estimated that 500 million people were infected with either syphilis , gonorrhea , chlamydia or trichomoniasis . At least an additional 530 million people have genital herpes and 290 million women have human papillomavirus . STIs other than HIV resulted in 142 , 000 deaths in 2013 . In the United States there were 19 million new cases of sexually transmitted infections in 2010 . Historical documentation of STIs date back to at least the Ebers papyrus around 1550 BC and the Old Testament . There is often shame and stigma associated with these infections . The term " sexually transmitted ___MASK18___ " is generally preferred over the terms " sexually transmitted disease " and " venereal disease ", as it includes those who do not have symptomatic disease .