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Rectal polyps b. Prostate cancer c. Condyloma acuminatum d. Hepatic carcinoma e. Carcinoma of the lung Reverse transcriptase is an enzyme unique to the retroviruses. Which one of the following is a function of the enzyme reverse transcriptase? DNase activity b. RNA isomerase activity d. Integration activity Louis encephalitis, a viral infection, was first recognized as an entity in Which of the following best describes SLE?
It is transmitted to humans by the bite of an infected tick b. It is caused by a togavirus c. It is the major arboviral cause of central nervous system infection in the United States d. It may present initially with symptoms similar to influenza e. There is considerable overlap of signs and symptoms seen in congeni- tal and perinatal infections.
Interferon, a protein that inhibits viral replication, is produced by cells in tissue culture when the cells are stimulated with which of the following? Botulinum toxin b. Synthetic polypeptides c. Viruses d. Chlamydiae e. Gram-positive bacteria Which one of the following statements best describes the cytopathic effects of viruses on host cells?
Usually morphological in nature b. Often associated with changes in mitochondrial membranes c. Pathognomonic for an infecting virus d. Rarely fatal to the host cell e.
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Can only be seen with an electron microscope A year-old girl presents with cervical lymphadenopathy, fever, and pharyngitis. Infectious mononucleosis is suspected. The most rapid and clinically useful test to make this diagnosis is a. IgM antibody to viral core antigen VCA b. IgG antibody to VCA c. Culture e. Which one of the following viruses would be most likely to establish a latent infection?
Measles virus c. Influenza virus d. Parvovirus e. Coxsackievirus group B A regimen that includes appropriately administered gamma globulin may be contraindicated in which one of the following diseases? Hepatitis A b. Hepatitis B c. Rabies d. Poliomyelitis e. Infectious mononucleosis Atypical lymphocytosis is most likely to be found in which one of the following diseases? Encephalitis caused by herpes simplex virus HSV b.
Mononucleosis induced by Epstein-Barr virus c. Parvovirus infection d. Chronic hepatitis C e. Rotavirus gastroenteritis A patient has arthralgia, a rash, lymphadenopathy, pneumonia but no fever. Which of the following diseases is most likely based on these symp- toms? Dengue fever b. Infectious mononucleosis d.
Hepatitis e. Hepatitis C HCV is usually a clinically mild disease, with only mini- mal elevation of liver enzymes. Hospitalization is unusual. Which one of the following statements best characterizes HCV? Few cases progress to chronic liver disease b. It often occurs in posttransfusion patients c. It is a DNA virus e. Blood products are not tested for antibody to HCV Which of the following markers is usually the first viral marker detected after hepatitis B infection?
HBeAg b. HBsAg c. HBcAg d. Anti-HBc e. HbeAb Which of the following may be the only detectable serological marker during the early convalescent phase of HBV infection window phase? HBeAb Which of the following is found within the nuclei of infected hepato- cytes and not usually in the peripheral circulation? Which one of the following viruses is the leading cause of congenital malformations? Rabies b. Rhinovirus c. Cytomegalovirus d. Mumps Orchitis, which may cause sterility, is a possible manifestation of which of the following?
Which of the following is a leading cause of pneumonia primarily in infants? Which of the following causes a fatal encephalitis for which a vaccine is available? Traditional vaccination for the common cold is virtually impossible because there are multiple serotypes of which one of the following viruses? Which of the following is available and effective for hepatitis A? Acyclovir b. Killed virus vaccine c.
Inactivated virus vaccine d. Live virus vaccine e. Recombinant viral vaccine Patients should be vaccinated annually for influenza with which of the following vaccines? Immune serum globulin b. The vaccine for measles is best characterized as a a. Bacterin b. Which one of the following would be the treatment of choice for HSV infection? Herpes immune globulin d. Azythromycin e. Which of the following best describes the presently available vaccine for hepatitis B? Synthetic peptide vaccine b. Chicken pox is a common disease of childhood. It is caused by which of the following viruses?
Varicella-zoster virus d. Papillomavirus Excluding influenza, which one of the following viruses is a common cause of acute respiratory disease? Human warts are not only cosmetically unsightly but may lead to can- cer of the cervix. They are caused by which one of the following viruses? A vaccine is available for one of the most common causes of infantile gastroenteritis.
However, it has recently been recalled. The virus is a. A child has mononucleosis-like symptoms yet the test for mononucle- osis and the EBV titers are negative. One of the causes of heterophile- negative mononucleosis is a. Toxoplasma b. Borrelia burgdorferi c. Rubella virus Lethargy, malaise, and fatigue are observed in a patient 2 weeks after eating raw hamburger at a restaurant. The most likely infectious cause is a. Cytomegalovirus c.
Salmonella e. Clostridium This disease is caused by a. Lymphogranuloma venereum e. Herpes simplex virus This virus may be detected by the polymerase chain reaction PCR in a variety of cells of patients with nasopharyngeal carcinoma. Mumps c. This virus causes a mononucleosis-like syndrome caused by a latent herpesvirus; it is often a congenital infection.
Large amounts of the virus are excreted in the urine; thus, urine becomes the fluid of choice for diag- nosis of this disease. Epstein-Barr virus b. HHV-6 d. Norwalk virus Questions 92—96 Assume you are asked by a resident what the most appropriate specimen is for the detection of a particular virus. Human papillomavirus a. Cervical tissue b. Synovial fluid c.
Blood d. Skin Cytomegalovirus a. Skin e. Cerebrospinal fluid Enterovirus a. Varicella-zoster virus VZV a. Stool e. Which of the following is transmitted by the fecal-oral route; can be acquired from shellfish; and often causes acute jaundice, diarrhea, and liver function abnormalities?
Norwalk virus d. Astrovirus e. Hepatitis A virus Which of the following is the second most common cause of pediatric gastroenteritis? Unlike other similar viruses, this virus causes only gas- troenteritis. Which of the following is the most common cause of pediatric gas- troenteritis? Which of the following is a common cause of epidemic gastroenteri- tis, particularly aboard cruise ships and in summer camps?
Which of the following is a cause of mild gastroenteritis? It can be transmitted by the fecal-oral route but not by food consumption. IgM antibody to the viral particle is the method of choice for labora- tory diagnosis of which one of the following hepatitis viruses? Hepatitis C d. Hepatitis D e. Hepatitis E This virus belongs to the family of flaviviruses and its reservoir is strictly human. Transmission is blood-borne so the blood supply is rou- tinely screened for this virus. Vaccination for this hepatic disease is with viral surface antigen and usually provides immunity. This hepatitis virus is a calicivirus.
The reservoir is in pigs, and humans acquire it via the fecal-oral route. This hepatitis virus is a defective virus in that it cannot replicate independently without the presence of hepatitis B virus. Which of the following is the causative agent of a variety of cutaneous warts plantar, common, and flat and is associated with cervical neoplasia? Human papillomavirus b. West Nile virus c. Tick-borne encephalitis virus d. Polyomavirus e. Subacute sclerosing panencephalitis virus SSPE Recently appearing in the United States, this virus is carried by birds, transmitted by mosquitoes, and infects humans and horses.
Which of the following viruses causes progressive multifocal leukoencephalopathy PML , a disease causing demyelination in the cen- tral nervous system? SSPE This virus is transmitted by the same arthropod that transmits babesiosis and ehrlichiosis. This virus is a single-stranded RNA orthomyxovirus. Annual vacci- nation is necessary because of antigenic drift and shift. Measles virus b. Influenza virus c. Respiratory syncytial virus d. Parainfluenza virus e. This virus is a single-stranded RNA paramyxovirus. This virus is the leading cause of bronchiolitis and community- acquired pneumonia in infants.
This is a paramyxovirus and causes the syndrome known as croup. This is a double-stranded DNA virus. The answer is c. Ryan, pp — A viral load of , copies per ml significantly increases the chance of progression to AIDS within 5 years. The other tests listed do not accurately predict pro- gression to AIDS. The figure below shows the basic structure of HIV including the enzyme, reverse transcriptase. The location of the envelope glycoproteins gp and gp is shown, as are the major viral core proteins p25, p17, p9, and p7.
The core protein, p17, is found outside the viral nucleoid and forms the matrix of the virion. RT indicates reverse transcriptase. Davis, pp — Raoult, p Parvovirus B 19 is the causative agent of erythema infectiosum fifth disease. It is associated with transient aplastic crisis in persons with hereditary hemolytic anemia.
In adults, it is also associated with polyarthralgia. Davis, p Raoult, pp — The initial infec- tion by herpes simplex virus is often inapparent and occurs through a break in the skin or mucous membranes, such as in the eye, throat, or gen- itals. Latent infection often persists at the initial site despite high antibody titers. Recurrent disease can be triggered by temperature change, emotional distress, and hormonal factors. Type 1 herpes simplex virus is usually, but not exclusively, associated with ocular and oral lesions; type 2 is usually, but not exclusively, associated with genital and anal lesions.
Type 2 infec- tion is more common. In addition to mucocutaneous infections, the CNS and occasionally visceral organs can be involved. The answers are 4-e, 5-e, 6-d. Levinson, pp — The combination of drugs work together as reverse tran- scriptive inhibitors and a protease inhibitor. The patient is infectious and his HIV antibody screening test will be positive. The high viral load, however, is not a predictor of response to therapy. Many patients with high viral loads do very well on triple therapy, although resistance to one or more of the agents may subsequently occur.
A low CD4 count does not predict pro- gression to AIDS but does indicate increased chance of opportunistic infec- tion such as those listed. While HIV-positive patients contract pneumococcal pneumonia, they are probably at no more risk than the general population, as protection against pneumococcal disease is linked to the presence of anticapsular antibody. Murray, pp — Infectious mononucleosis is most common in young adults 14 to 18 years of age and is very rare in young children.
Heterophil antibody titer is helpful in diagnosis, but is not expressed as a function of clinical recovery. The answer is b. Rubella virus does not pro- duce cytopathic effects CPEs in tissue-culture cells. Moreover, rubella- infected cells challenged with a picornavirus are resistant to subsequent infection and thus would not exhibit CPEs. Monkey kidney cells infected only with picornavirus would show CPEs. The answer is a.
Arboviruses arthropod- borne viruses may or may not be surrounded by a lipid envelope, although most are inactivated by lipid solvents such as ether and may con- tain either double-stranded or single-stranded RNA. Physicochemical stud- ies have demonstrated a great heterogeneity among these viruses. Arboviruses cause disease in vertebrates; in humans, encephalitis is a fre- quent arbovirus illness. Most human infections with arbovirus, however, are asymptomatic. The answer is d. Interferon is a protein pro- duced by cells in response to a viral infection or certain other agents.
Enter- ing uninfected cells, interferon causes production of a second protein that alters protein synthesis. As a result of inhibition of either translation or transcription, new viruses are not assembled following infection of inter- feron-protected cells. Coronaviruses, discovered in , are thought to be a major agent of the common cold, especially in older children and adults. The virion is known to contain RNA, but other ele- ments of its structure are unclear.
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The delta agent was first described in and has recently been shown to be an incomplete RNA virus that requires HBsAg for replication. It is found most often in persons who have multiple parenteral exposures, for example, intravenous IV drug abusers, hemophiliacs, and multiply transfused patients. As an intravenous agent, rib- avirin is effective against Lassa fever in the first week of onset of the disease.
It may also be administered as an aerosol that is quite useful in infants with RSV. Unlike amantadine, which is efficacious only with influenza A, rib- avirin has activity against both influenza A and B if administered by aerosol in the first 24 h of onset. Levinson, p Echoviruses were discovered acci- dentally during studies on poliomyelitis. Echoviruses range in size from 24 to 30 nm in diameter and contain a core of RNA. HSV meningitis or encephalitis is difficult to diagnose by laboratory tests as there is a low titer of virus present in the CSF.
Neonatal HSV infects the child during the birth process. While culture, Tzanck smear, and even antibody tests may be use- ful in adults, particularly those with HSV-rich lesions, they are not useful for CSF testing. Once diagnosed rapidly, HSV encephalitis or meningitis can be treated with acyclovir. Enterovirus and Coxsack- ievirus A can be recovered from conjunctival scrapings of patients with acute hemorrhagic conjunctivitis AHC during the first 3 days of illness.
Isolation rates are somewhat higher for enterovirus than Coxsackievirus. The answer is e. For example, natural mumps infection confers immunity after a sin- gle infection, even if the infection was a unilateral, not bilateral, parotitis. The majority of patients with mumps do not develop systemic manifestations. Last, the virus is maintained exclusively in human populations; canine reservoirs are not known. The mumps vaccine is a live attenuated virus vaccine derived from chick-embryo tissue culture.
Clinical manifestations of cytomegalovirus CMV infection may not be readily apparent at birth. Thus, in a newborn infant with a titer of CMV, it is necessary to deter- mine whether the antibodies were passed transplacentally from the mother these antibodies would be IgG or produced by the fetus in response to an in utero infection IgM. A newborn infant who is infected excretes large numbers of virus particles in the urine and, therefore, places other neonates at risk for contracting CMV disease. The measles virus is a paramyxovirus.
In industrialized countries, vaccination has reduced the importance of this childhood infec- tion although U. In developing countries, however, measles is a major killer of young children. In America, most states now require proof of immunity before school enrollment, and this has reduced the incidence of disease. Human papillomavirus HPV is the cause of genital warts. It is one of the most pervasive of all the sexually transmitted diseases. There is no specific cure or vaccine. There are multiple serotypes of papillomavirus and some serotypes are linked to cer- vical cancer.
New techniques for molecular diagnosis of HPV show promise for rapid and sensitive detection and perhaps more aggressive treatment. Parainfluenza viruses are important causes of respiratory diseases in infants and young children. The spectrum of disease caused by these viruses ranges from a mild febrile cold to croup, bronchiolitis, and pneumonia. Parainfluenza viruses contain RNA in a nucleocapsid encased within an envelope derived from the host cell membrane. Infected mammalian cell culture will hemabsorb red blood cells owing to viral hemagglutinin on the surface of the cell.
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Hepatitis E is a newly rec- ognized single-stranded RNA virus in the calicivirus family. Like HAV, it is enter- ically transmitted but there is no vaccine available nor routine detection test. Chronic liver disease does not occur, and because it is not blood-borne it is of no threat to the blood supply. Aseptic meningitis is char- acterized by a pleocytosis of mononuclear cells in the cerebrospinal fluid; polymorphonuclear cells predominate during the first 24 h, but a shift to lymphocytes occurs thereafter. The cerebrospinal fluid of affected persons is free of culturable bacteria and contains normal glucose and slightly elevated protein levels.
Peripheral white blood cell counts usually are normal. Although viruses are the most common cause of aseptic meningitis, spiro- chetes, chlamydiae, and other microorganisms also can produce the disease. Levinson, pp , , HBsAg would be present in either a new infec- tion or in the carrier state, while HBsAb would not be present in either case.
In a small number of patients with acute hepatitis B infection, HBsAg can never be detected. In others, HBsAg becomes negative before the onset of the disease or before the end of the clinical illness. Eastern equine encephalitis EEE is a severe disease usually seen in the summer months when Aedes mosquitoes are prevalent.
In and , there were several outbreaks in the Northeast United States. Control of EEE is a function of mosquito eradication. Horses and humans are accidental hosts. While draining of swamps helps, other measures to eliminate mosquitoes such as spraying are the most effective. Recurrent disease in adults who possess circulating antibody against varicella-zoster virus may be more severe and cause an inflamma- tory reaction in the sensory ganglia of spinal or cranial nerves.
This disease, shingles, appears to result from the reactivation by trauma or other stim- uli of latent varicella-zoster virus. Rhinovirus is a major cause of the common cold. The primary mode of transmission is the contact of contaminated hands, fingers, or fomites with the conjunctiva or nasal epithelium. While several studies have shown no evidence of aerosol trans- mission, a study by Dick and associates in did show aerosol trans- mission can occur. This is not, however, the main mode of transmission.
Measles rubeola is an acute, highly infectious disease characterized by a maculopapular rash. Ger- man measles rubella is an acute, febrile illness characterized by a rash as well as suboccipital lymphadenopathy. Incubation time is 9 full days after exposure. Onset is abrupt and symptoms mostly catarrhal. The definitive diagnosis of rabies in humans is based on the finding of Negri bodies, which are cyto- plasmic inclusions in the nerve cells of the spinal cord and brain, especially in the hippocampus.
Negri bodies are eosinophilic and generally spherical in shape; several may appear in a given cell. Negri bodies, although pathognomonic for rabies, are not found in all cases of the disease. Kuru and Creutzfeldt- Jakob disease CJD are similar but not identical diseases with very differ- ent epidemiology. Kuru is prevalent among certain tribes in New Guinea who practiced ritual cannibalism by eating the brains of the departed. CJD is found worldwide and has been transmitted by corneal transplants and in pituitary hormone preparations. Prions are unconventional self- replicating proteins, sometimes called amyloid.
It is now thought that CJD, Kuru, and animal diseases such as scrapie, visna, and bovine spongiform encephalopathy Mad Cow Disease are caused by prions. Routine vaccination of infants and children for smallpox has been discontinued in the United States, both because the risk of contracting the disease is so low and because the complications of smallpox vaccination, including generalized vaccinia eruption, postvaccinal encephalitis, and fetal vaccinia, are signifi- cant. Owing to the extremely effective eradication of smallpox worldwide by the World Health Organization, U.
Pregnancy, immune deficiencies, and eczema and other chronic dermatitides are contraindications to smallpox vaccination. Hepatitis D virus is a defective virus with an RNA genome and a hepatitis B surface antigen envelope. Diagnosis is made by demonstrating IgM or IgG antibodies, or both. Herpes simplex virus can infect the conjunctiva and is among the most common causes of blind- ness in North America and Europe.
The e antigen seems to be related to the Dane particle, which is presumed to be the intact hepatitis B virus. Possession of the e antigen suggests active disease and, thus, an increased risk of transmission of hepatitis to others. HBsAg and e antigen are components of hepatitis B and are not shared by other hepatitis viruses. Louis encephalitis, yel- low fever, and dengue are caused by flaviviruses. Western equine encephali- tis is caused by an alphavirus.
Laboratory diagnosis is usually made by demonstration of a fourfold rise in specific antibody titer in paired sera. Intravenous administration has proved effective in treating Lassa fever. Ryan, p Herpes simplex virus causes primary and recurrent disease. The typical skin lesion is a vesicle that contains virus particles in serous fluid. Giant multinucleated cells are typically found at the base of the herpesvirus lesion. Encephalitis, which usually involves the temporal lobe, has a high mortality rate.
Severe neurologic sequelae are seen in surviving patients. Contact with infected secre- tions such as saliva can result in infection with EBV, thus the term kissing disease. Laboratory diagnosis of EBV-induced infectious mononucleosis is usually determined by presence of atypical lymphocytes, heterophile anti- bodies, or specific antiviral antibodies such as VCA viral capsid antibody. Baron, pp — Respiratory syncytial virus RSV is the most important cause of pneumonia and bronchiolitis in infants.
The infection is localized to the respiratory tract. The virus can be detected rapidly by immunofluorescence on smears of respiratory epithe- lium. In older children, the infection resembles the common cold. Aerosolized ribavirin is recommended for severely ill hospitalized infants.
Howard, pp — Many believe that casual contact with patients who are HIV-positive increases the risk of acquiring the disease. This is not the case. It is also clear that homosexual females have a low rate of HIV acquisition. Because a substantial portion of the blood supply in Central African countries is HIV-infected, hospitalization is risky particularly if transfusion is necessary. The highest risk of fetal infection with rubella occurs during the first trimester. However, before other mea- sures such as termination of pregnancy are considered, a rubella immune status must be performed.
A rubella titer of is protective. Mad Cow Disease is related to both scrapie in sheep and bovine spongiform encephalopathy virus. Theoretically, such acquisition could be through ingestion of beef from infected cows. A prion consists of protein material without nucleic acid.
While related to a virus, a prion is a proteinaceous infectious particle that replicates within cells. It is transmitted enterically, and the disease is often referred to as enteric hepatitis C. There is no test for HEV routinely available. Diagnosis is clinical and also one of exclusion. Levinson, pp 47, Staphylococcus aureus is the most common cause of postinfluenzal secondary bacterial pneumonia.
It most often affects the elderly, although patients of any age may be afflicted. The pneumococcus as well as group A streptococci and Haemophilus influenzae may also cause pneumonia. Colorado tick fever, spread by the wood tick, causes fever, headache, retro-orbital pain, and severe myalgia. Fever and jaundice char- acterize yellow fever, a life-threatening disease spread by mosquitoes. Fol- lowing fever, headache, myalgias, and photophobia, the symptoms progress to the liver, kidney, and heart.
Mortality rate is high. Dengue fever shares the same mosquito vector as yellow fever. Classic dengue fever breakbone fever includes flu-like symptoms. Severe muscle and joint breakbone pain occurs. Coxsackievirus is spread by the fecal-oral route. In , an outbreak of a fatal respiratory disease occurred in the southwestern United States. This dis- ease is caused by a Hantavirus endemic in deer mice. It is not transmitted from person to person. Ribavirin has been used but is not effective.
A vaccine is not available. Called fifth disease, it is the fifth childhood rash disease; the other four are measles, rubella, scarlet fever, and roseola. Only two human viruses have been confirmed as human tumor viruses. The virus that causes chicken pox VZV is not know to be oncogenic. Adenoviruses are wide- spread and cause a variety of clinical problems.
Parvovirus B19, not adenovirus, causes acute hemolytic anemia. Tilton, — Although infection with cytomegalovirus CMV is common, it only rarely causes clinically apparent disease. Children and adults with immunosuppressive problems are susceptible to active disease. The patient suffers blurring of vision or vision loss, and ophthalmic examination reveals large yellowish-white areas with flame-shaped hemorrhages.
Rotaviruses were initially identified by direct electron microscopy EM of duodenal mucosa of infants with gastroenteritis. They are non-lipid-containing RNA viruses with a double-shelled capsid. Although the virus has been serially propagated in human fetal intestinal organ cultures, cytopathic changes are minimal or absent; multiplication is detected by immunofluorescence.
Numerous methods for rotavirus anti- gen detection, including radioimmunoassay, counterimmunoelectrophore- sis, and enzyme-linked immunosorbent assay, have been developed and found to be about as effective as EM. SSPE is a late and rare man- ifestation of measles. It is a progressive encephalitis involving both white and gray matter. Rotavirus is a viral entity that is similar to Nebraska calf diarrhea virus and is thought to be a major cause of acute diarrhea in newborn infants.
Three-quarters of all adults have antibodies against rotavirus; passive transfer of these antibodies to the baby, especially through the colostrum, seems to be protective. Although vaccination would be expected to be of little use to the neonate, it might effectively immunize pregnant mothers. Both mumps and measles are well-recognized paramyxovirus infections.
This group also includes parainfluenza virus, which causes laryngotracheobronchitis croup in children, and respiratory syncytial virus, which can cause bronchiolitis in infants. Paramyxoviruses have glycoprotein spikes that extend their lipid membrane and are responsible for hemagglutination activities. Papillomavirus infects the skin or mucosa and causes benign tumors. The lesion is termed condyloma acuminatum.
These tumors may undergo malignant conversion and become squamous cell carcinomas. Classification of the human papillo- mavirus is done by DNA hybridization, and to date 46 types have been rec- ognized.
Some types, such as 16 and 18, are more frequently associated with carcinoma, while others, such as 6 and 11, are associated with benign tumors or warts. The replication of a retroviral genome is dependent on the reverse transcriptase enzyme, which performs a variety of functions. Louis encephalitis virus has structural and biologic characteristics in common with other flaviviruses. It is the most important arboviral disease in North America.
Patients who contract the disease usually present with one of three clinical mani- festations: febrile headache, aseptic meningitis, or clinical encephalitis. See figure below. Presently, cytomegalovirus CMV is the most common cause of congenital and peri- natal viral infections. Culture of the virus is a sensitive diagnostic tech- nique; in the case of a neonate with classic symptoms, serum samples from the mother and neonate are obtained at birth.
For this reason, another sample from the infant at 1 month of age is tested simultaneously with the initial sample. The results should indicate a rise in IgM titer. Interferon is a protein that alters cell metabolism to inhibit viral replication. It induces the formation of a second protein that interferes with the translation of viral messenger RNA. Interferon confers species-specific, not virus-specific, protection for cells.
Murray, p Viruses may produce cytopathic changes without forming infectious virions and without replicating infectious virus, although the cytopathology is usually fatal to the cell. A particular cyto- pathic effect is not necessarily associated with a specific virus. Antibodies to EBNA should be absent, as they usually appear 2 to 3 months after onset of illness. Culture is not clinically useful because it 1 requires freshly fractionated cord blood lymphocytes, 2 takes 3 to 4 weeks for completion, and 3 is reac- tive in the majority of seropositive patients.
The virus has also been cultured from mesenteric lymph nodes, and, in rare cases, viral DNA has been detected in peripheral lymphocytes. Recurrent illness usu- ally does not arise from these latent infections; however, activation can occur in the immunosuppressed. A therapeutic regimen that includes appropriately administered gamma globulin is effective in the treatment of viral hepatitis A and B.
Hyperimmune rabies antiserum prolongs the incu- bation period of rabies and allows the patient more time to mount an immune response to the vaccine. Although it is not a primary form of treat- ment for patients with poliomyelitis, passive immunization with pooled gamma globulin can offer adequate protection against the disease. They are also seen in other diseases, including cytomegalovirus infection, viral hepatitis, toxoplasmosis, rubella, mumps, and roseola.
Dengue breakbone fever is caused by a group B togavirus that is transmitted by mosquitoes. The clin- ical syndrome usually consists of a mild systemic disease characterized by severe joint and muscle pain, headache, fever, lymphadenopathy, and a maculopapular rash. Hemorrhagic dengue, a more severe syndrome, may be prominent during some epidemics; shock and occasionally death result. About half of HCV patients develop chronic hepatitis.
A large number of infections appear among IV drug abusers. The answers are b, d, a, c. Advances in the serodiagnosis of viral hepatitis have been dra- matic, and the findings of specific viral antigens have led to further eluci- dation of the course of infections. It appears in the blood early after infection, before onset of acute illness, and persists through early con- valescence. HBsAg usually disappears within 4 to 6 months after the start of clinical illness except in the case of chronic carriers. Hepatitis B 37 antigen HBeAg appears during the early acute phase and disappears before HBsAg is gone, although it may persist in the chronic carrier.
Persons who are HBeAg-positive have higher titers of HBV and therefore are at a higher risk of transmitting the disease. The hepatitis B core antigen HBcAg is found within the nuclei of infected hepatocytes and not generally in the peripheral circulation except as an integral component of the Dane particle. The antibody to this antigen, anti-HBc, is present at the beginning of clinical illness.
The answers are c, e, d, a, b. Levinson, pp —, —, —, — The rabies virus is transmitted by the bite of a rabid animal. It almost always causes a fatal encephalitis if untreated. Postexposure treatment includes use of a killed vaccine and human rabies globulin HIG. Rhinoviruses are the most prominent cause of the common cold. Many serotypes exist, which may account for their ability to cause frequent disease.
Cytomegalovirus causes cytomegalic inclusion disease CID , especially congenital abnormalities, in neonates. Malformations include microencephaly. Seizures, deafness, jaundice, and purpura can also occur. CID is also one of the leading causes of mental retardation in the United States. Respiratory syncytial virus RSV is the leading cause of pneumonia and bronchiolitis in infants. Viremia does not occur and treatment in several ill infants is aerosolized ribavirin. Orchitis, a complication of mumps virus infection in postpubertal males, can cause sterility if bilateral.
The answers are b, c, d, a, e. Levinson, pp —, — The original vaccine for hepatitis B was prepared by purifying hepatitis B surface antigen HBsAg from healthy HBsAg-positive carriers and treating it with viral-inactivating agents. The second-generation vaccine for hepatitis B is produced by recombinant DNA in yeast cells con- taining a plasmid into which the gene for HBsAg has been incorporated.
Influenza usually occurs in successive waves of infection with peak incidences during the winter months. If only minor antigenic drift is expected for the next influenza season, then the most recent strains of A and B viruses representative of the main antigens are included in the vac- cine. Influenza vaccine consists of killed viruses. Live attenuated measles virus vaccine effectively prevents measles. Protection is provided if given before or within 2 days of exposure. Vacci- nation confers immunity for at least 15 years.
Acyclovir is an analogue of guanosine or deoxyguanosine that strongly inhibits herpes simplex virus HSV but has little effect on other DNA viruses. When employed for the treatment of primary genital infection by HSV, both oral and intravenous formulations have reduced viral shedding and shortened the duration of symptoms.
The vaccine for hepatitis A virus HAV is prepared from virus grown in culture and inactivated with formalin. The answers are c, d, e, b, a. Varicella-zoster virus is a her- pesvirus. Chickenpox is a highly contagious disease of childhood that occurs in the late winter and early spring. It is characterized by a generalized vesicular eruption with relatively insignificant systemic manifestations.
Adenovirus has been associated with adult respiratory disease among newly enlisted military troops. Crowded conditions and strenuous exercise may account for the severe infections seen in this otherwise healthy group. Papillomavirus is one of two members of the family Papovaviridae, which includes viruses that produce human warts. These viruses are host- specific and produce benign epithelial tumors that vary in location and clinical appearance. The warts usually occur in children and young adults and are limited to the skin and mucous membranes.
Rotavirus is worldwide in distribution and has been implicated as the major etiologic agent of infantile gastroenteritis. Infection with this virus varies in its clinical presentation from asymptomatic infection to a rela- tively mild diarrhea to a severe and sometimes fatal dehydration. The exact mode of transmission of this infectious agent is not known. Because of severe side effects, the rotavirus vaccine has been recalled and is temporar- ily unavailable.
Infectious mononucleosis caused by cytomegalovirus CMV is clini- cally difficult to distinguish from that caused by Epstein-Barr virus. Lym- phocytosis is usually present with an abundance of atypical lymphocytes. CMV-induced mononucleosis should be considered in any case of mononucleosis that is heterophil-negative and in patients with fever of unknown origin. The answers are c, a, c, e, b. Epstein-Barr virus EBV is a herpesvirus that causes a number of syndromes; the most common is infectious mononucleosis.
It is a ubiq- uitous enveloped DNA virus. Only one serotype of EBV has been recog- nized, although molecular methods have reorganized a number of genotypes of EBV. Infectious mononucleosis is an acute disease most commonly seen in younger people. It is characterized by a proliferation of lymphocytes, lymph node enlargement, pharyngitis, fatigue, and fever. Infection in young children is usually either asymptomatic or characteristic of an acute upper respiratory infection.
Heterophil antibodies are those that occur in one species human and react with antigens of a different species. Definitive diagnosis is made by detection of antibodies to EBV components. Similar mononucleosis-like diseases are caused by cytomegalovirus CMV and Toxoplasma gondii, a parasite. Congenital infection with CMV almost always causes serious sequelae, such as retardation and hearing loss. Although CMV and T. The answers are a, c, e, d, d. The diagnosis of a viral infection is made easier by the creation of a greater number of diagnostic virology laboratories during the past few decades.
In order for viral diagnosis to be successful, the most appropriate specimen must be collected for the disease in question. Human papillomavirus HPV is often detected microscopically in cer- vical biopsies. Evidence suggests that some HPV serotypes are more likely than others to cause cervical cancer.
Many viruses have a viremic phase, but only a few, such as CMV, per- sist after the patient becomes symptomatic. CMV can be isolated from lymphocytes and polymorphonuclear leukocytes. This usually requires special separation procedures particularly in those compromised patients who may be neutropenic. Enteroviruses such as echoviruses and coxsackieviruses are the pre- dominant cause of aseptic viral meningitis. While enterovirus infections are often diagnosed by specific antibody response, it is possible to isolate the virus from CSF. Detection and identification of these viruses is essen- tial because of the availability of antiviral agents such as acyclovir.
Other viruses, such as enteroviruses and paramyxoviruses, cause skin lesions. Many viruses can be isolated from feces. Norwalk agent and other caliciviruses may also be isolated or detected from stools, but usually only in specialized laboratories. The answers are e, b, a, c, d. A number of viruses that cause gastroenteritis are now being rec- ognized. The table on page 51 summarizes the characteristics of rotavirus, Norwalk virus, adenovirus, calicivirus, and astrovirus. The answers are a, c, b, e, d. Detection of anti-HAV IgM in a single serum spec- imen obtained in the acute or convalescent stage is the quickest and most reliable method to diagnose hepatitis A infection.
This antibody is usually present at onset of symptoms and may persist 3 to 6 months. Several epidemiologic studies have demonstrated that immune serum globulin ISG can prevent clinical hepatitis A even when given up to 10 days after exposure. Similar studies have shown that ISG was able to decrease the incidence of hepatitis B infec- tion in exposed persons.
The viral reservoir is human.