More than 50 human papillomavirus strains (types) have been reported. The most common clinical manifestations are warts (on skin) and condylomata (papilloma lesions) in the genital area. HPV-1 is usually associated with warts on the sole of the foot and HPV-2 in nonplantar skin warts. In the female cervix, HPV-6 and 11 are found most often in flat benign condylomatous lesions and low-grade cervix dysplasia (CIN I and II), while types 16 and 18 are found in 80%-95% of patients with high-grade cervical dysplasia or carcinoma in situ (CIN III) and are also associated with some cases of carcinoma of the penis. There is also an association (although less strong) of type 16 with squamous carcinoma in situ of anogenital skin (Bowen’s disease) and invasive anal carcinoma. Diagnosis is most often made with immunohistologic stains or nucleic acid (DNA) probe methods on cervix biopsy specimens. Cervix biopsy produces considerably more positive results than cervical scrape specimens (four times more in one study). In one study, about one third of women with HPV infection had visually evident cervical lesions, about one third had no visible lesions but had HPV infection demonstrated by cytology, and the infection was demonstrated in about one third only by nucleic acid probe. All commercially available DNA probe kits are not equally sensitive.
Month: July 2009
-
Influenza Virus
Influenza produces upper and lower respiratory tract infection. There are 3 major types or subgroups: A, B, and C. Antigenic mutations occur frequently in type A, permitting reinfection; but are much less common in types B and C. The best laboratory test is culture of nasopharyngeal secretions, especially by the newer and much more rapid (2-4 days) shell-vial culture technique. Antibody detection is available by CF, IFA, and ELISA. IgM and IgG can be assayed. Acute and convalescent specimens are needed unless the initial CF or IgM antibody response is positive in high titer (both CF and IgM antibody disappear in a few weeks). A rapid membrane-filtration cartridge EIA method is commercially available for influenza A virus, which was found to have 90% sensitivity (compared to culture) using nasopharyngeal washings and 39% sensitivity using pharyngeal gargle samples.
-
Respiratory Syncytial Virus
Respiratory syncytial virus (RSV) is the most common cause of severe lower respiratory illness of infants and young children, causing 5%-40% of pneumonias and 60%-90% of bronchiolitis episodes. Peak incidence is at 2-3 months of age. About 30%-50% of children have been infected by 12 months of age and about 95% by age 5 years. However, no significant clinical immunity is produced; repeat infections may occur, and persons of any age may develop acute infection. The most common clinical illness is upper respiratory tract infection similar to the common cold. The virus is spread through airborne droplets. The incubation period is 2-8 days. Diagnosis can be made by culture, by tests for antigen, and by tests for antibody. The best specimen for culture is nasal washings; the next best is nasopharyngeal swab. In either case, the specimen should include cells from the posterior nose and pharyngeal epithelium, since they contain the virus. Swab specimens should be placed immediately into a transport medium, and any specimen should be placed into wet ice. However, culture is expensive, and usually must be sent to a reference laboratory with wet ice. Standard culture methods take 4-14 days; and shell-vial methods, 2-3 days. The virus survives only about 4 days at 4°C and dies quickly at ordinary freezer temperatures or at high temperatures. Culture (under optimal conditions) is still considered the gold standard for diagnosis. However, some investigators report less than optimum results (69%-83% sensitivity), especially with mailed-in specimens. Antibody detection methods include immunofluorescence and ELISA. Antibody detection methods have several drawbacks: the fact that sensitivity is often less than 50% in infants less than 3 months old; the need for acute and convalescent specimens unless sufficiently elevated IgM titers are present; and the necessity in most cases to send the serum specimens to a reference laboratory. Methods for antigen detection in patient specimens are also available,including fluorescent antibody and ELISA, with same-day results. Nasopharyngeal aspirates are reported to provide the best specimens. Compared to culture, sensitivity of these methods are about 80%-90% (range, 41%-99%). Antigen detection methods may be positive on some specimens that are negative by culture, especially with mailed-in specimens. Antigen detection is rapidly replacing culture and antibody detection for diagnosis of RSV infection. However, the sensitivity of different manufacturers’ kits may differ considerably.
-
Mumps
Mumps is a disseminated virus infection, although the main clinical feature is salivary gland enlargement. Evidence of nonsalivary gland involvement is most commonly seen in adults. In men, orchitis (usually unilateral) is reported in about 20% of cases. Adult women occasionally develop oophoritis. Persons of any age may be affected by meningoencephalitis, the most serious complication of mumps. This is reported in 0.5%-10% of patients. Many persons with CSF changes are asymptomatic. Females are affected five times more frequently than males. Complications of mumps may appear before, during, or after parotitis, sometimes even without clinical parotitis. Diagnosis is made by culture or serologic tests. Saliva is probably best for culture; mouth swabs or CSF can be used. Serologic tests require acute and convalescent serum specimens.
-
Measles
Measles (rubeola) is still important, even though widespread vaccination has begun. Measles is spread by droplet inhalation. Incubation lasts about 9-11 days, followed by 3-4 days of fever, cough, and sometimes conjuctivitis. Koplik’s spots appear on the oral mucosa in 50%-90% of patients about 2-3 days after symptoms begin. These last about 6-7 days. The typical measles skin rash begins about 4-5 days after onset of upper respiratory tract symptoms. The two main complications are encephalitis and pneumonia. Fortunately, encephalitis is rare, the incidence being 0.01%-0.2%. Due to the great frequency of the disease, however, the total number of cases is appreciable. About one third of those with encephalitis die, one third recover completely, and the remainder survive but show moderate to severe residua. Measles encephalitis is considered postinfectious because it develops 4-21 days after the onset of rash. Measles involves lymphoid tissue and respiratory epithelium early in the illness. Therefore, bronchitis, bronchiolitis, and pneumonia are fairly frequent. Most cases of pneumonia are due to superimposed bacterial infection (staphylococci, pneumococci, streptococci), but some are caused directly by the rubeola virus. Secondary bacterial otitis media is also fairly frequent. For diagnosis, culture and serologic tests are available. Standard culture takes 7-10 days. Culture depends on the stage of disease. For a period of 1 week ending with the first appearance of the rash, blood, nasopharyngeal swabs, or urine provide adequate specimens. After appearance of the rash, urine culture is possible up to 4 days. Beyond this, culture is not useful, and serologic tests must be employed using acute and convalescent serum specimens. Measles HI-detectable antibodies appear about the end of the first week after appearance of the rash and peak about 2 weeks later. Measles IgM antibody appears about 2 days following rash onset, peaks about 10-14 days after rash onset, and becomes undetectable at about 30 days. Interpretation is similar to that of rubella tests. However, one report indicates about 30% false negative IgM results even 3 weeks after disease onset. IgG acute and convalescent serum specimens can also provide a diagnosis.
-
Parvovirus B19
Parvovirus B19 belongs to a genus that infects both animals and humans. These are small DNA viruses without an outer envelope. Replication appears to take place in erythroid precursors of the bone marrow. The two most common diseases produced are erythema infectiosum (“fifth disease”), a condition somewhat resembling rubella, but with a rash that has a somewhat different body distribution; and transient aplastic crises. Both are more frequent in children. In both conditions, the incubation period is about 5-15 days, but may be as long as 20 days. In both conditions there may be a viral-type prodrome with fever, malaise, and other symptoms. Most patients with aplastic crises due to B19 already have some type of hemolytic anemia (such as sickle cell disease), either congenital or acquired. Immunocompromised patients (such as those with HIV-1 infection) can also have aplastic crises. It is thought that B19 infection is responsible for 90% of aplastic crises in patients with these conditions.
IgM antibody becomes detectable in the second week after infection and IgG antibody during the third week. IgM antibody decreases to nondetectable levels at roughly 6 months but can persist longer. The most commonly used tests are EIA for IgM antibody and nucleic acid (DNA) probe methods for viral antigen in serum or body fluids during acute illness. These tests would usually have to be obtained at large reference laboratories or university centers.
-
Varicella-Zoster Virus (VZV)
Varicella-zoster virus (VZV) is a member of the herpesvirus group. Infection is spread through direct contact with skin lesions or through droplet inhalation. The incubation period is about 14 days (range, 9-21 days). Primary infection is usually varicella (chickenpox). The period of skin rash lasts about 4-6 days. This may be preceded by a short prodromal period. The period of contagion is said to be from 2 days before the rash until no new skin lesions appear and all old ones become crusted. Usually there is lifelong immunity to new infection (although not always). Complications are not common but are not rare. They include pneumonia, encephalitis, and Reye’s syndrome (20%-30% of Reye’s syndrome follows varicella infection). Incidence and severity of complications are increased in immunocompromised persons. Twenty-three percent to 40% of bone marrow transplant patients develop primary VZV infection or reinfection. Varicella infection in pregnancy may affect the fetus in 5%-10% of cases.
After the varicella syndrome is over, the virus begins a latent period in sensory nerve ganglion cells. Later on, it may reactivate in the form of zoster. Reactivation is more common in persons with malignancy or in those who are immunocompromised. It becomes more frequent with increasing age. About 10%-20% of the population is affected. Neuralgia is the most frequent symptom. A rash is also relatively frequent, often in the distribution of a dermatome. Encephalitis, sensory and motor neurologic abnormality, and ocular abnormality may occur.
Laboratory tests include Tzanck test smears of varicella-zoster lesions. Sensitivity is said to be 50% or less in varicella and 80% or less in zoster. This procedure is described in the section on simplex and the microscopic appearance is the same. Culture of lesions can be done, but results in varicella are reported to be 34%-78% positive and in zoster to be 26%-64%. Serologic tests can be done using fluorescent antibody (FA), ELISA, and slide LA. EIA is said to be 50% sensitive (range, 36%-94%); FA, about 75% (range, 69%-93%); and LA, about 60% (52%-76%). It appears that antibody production (and, therefore, sensitivity) is greater in otherwise healthy children than in adults. IgM antibody rises in varicella about 5-6 days after the rash begins and peaks at about 14 days; it rises in zoster about 8-10 days after onset of the rash and peaks at about 18-19 days. Some patients with VZV infection who later are infected by herpesvirus type 1 experience an anamnestic rise in VZV antibody. Nucleic acid (DNA) probe methods have also been reported for skin lesions and for CSF specimens.
-
Human Herpesvirus 6 (HHV-6) and 7 (HHV-7)
Human herpesvirus 6 (HHV-6) was first isolated and characterized in 1986. It infects predominately T-lymphocytes of the CD4 (helper) type, but also B-lymphocytes, megakaryocytes, and probably other cells. It is the sixth described member of the Herpesvirus family (the others being HSV-1, HSV-2, EBV, CMV, and varicella-zoster). Infection takes place mainly in the first 2-3 years of life, with antibodies detected in 52% to “almost all” (over 90%) of young children and up to 80% of adults. Similar to the other herpesviruses, a lifelong low-grade or latent infection is produced and reactivation may occur. HHV-6 is now well accepted as the cause of exanthema subitum (roseola infantum). Evidence has been presented for possible involvement in other conditions, such as heterophil-negative mononucleosis, transient febrile illnesses in children, and a type of chronic fatigue syndrome with CNS involvement centered in Nevada and California. One report suggests a role in idiopathic bone marrow transplant failure, seen in about 20% of bone marrow transplants. There is some reported serologic evidence of HHV-6 reactivation associated with CMV infection.
Tests have been described to detect HHV-6 IgG antibody, mostly fluorescent immunoassay and ELISA. Tests for antigen in patient peripheral blood monocytes have also been described, both fluorescent immunoassay and nucleic acid probe with PCR amplification. These tests are currently available only in research laboratories or large reference laboratories.
HHV-7 was identified in 1990. It is frequently found in saliva and apparently causes frequent subclinical infection similar to HHV-6. Also similar to HHV-6, HHV-7 has been reported to cause some cases of exanthema subitum in young children. Serologic testing for IgG antibody has been reported using indirect immunofluorescent methodology.
-
Herpes Simplex (HSV)
HSV infection is characterized by a primary infection, often asymptomatic, after which the virus remains dormant in the dorsal root ganglia of peripheral nerves interrupted in some patients by one or more episodes of recurrent disease. Primary infection usually requires a person without preexisting HSV antibody. However, a person can have antibody against one strain of HSV (from previous infection) and become infected by a different strain (reinfection as opposed to reactivation or recurrence of preexisting disease). Primary infection or reinfection is usually acquired from close contact with an infected person: the mouth in cases of nongenital infection, and sexual intercourse in cases of genital infection. However, transmission can occur through body secretions. Immunocompromised persons are at increased risk of primary HSV infection and reactivation. There are two closely related but distinct types of HSV that share some antigens but not others. Herpes simplex virus type 1 (HSV-1) typically produces nongenital infections of various types such as lesions of the mouth, blisters on the mucous membrane border of the lips (“canker sores,” or “cold sores”), keratitis (corneal ulcers of the eye), focal lesions of the fingers (“Whitlow”), and encephalitis (most frequently involving the temporal lobes of the brain). Occasional immunocompromised patients develop disseminated HSV-1 disease. At one time about 90% of the population was found to have antibodies against HSV-1, but more recently this incidence is said to have fallen to about 25%-50%. About 20%-45% of patients with HSV-1 oral lesions eventually develop recurrence. Herpes simplex virus type 2 (HSV-2) produces blistering lesions (vesicles) on the genitalia of males and females and is considered a venereal disease. Reports indicate that HSV-2 causes 20%-50% of genital ulcerations in U.S. sexually transmitted disease clinics. About 5%-15% of patients with genital herpes have HSV-1 isolated rather than HSV-2, and one report indicates that up to 20% of labial or facial lesions are due to HSV-2 rather than HSV-1. About 85% of persons with HSV-2 with genital lesions have recurrences.
In primary HSV-2 genital infection that is symptomatic, the incubation period is about 5-7 days (range, 1-45 days). About one half of the patients (range, 39%-68%) develop systemic symptoms (e.g., fever, malaise, myalgia, and headache), including a subset of about 25% (range, 13%-36%) of all patients who experience a mild self-limited episode of aseptic meningitis (which has a marked difference in severity and prognosis from the severe brain infection of HSV-1). Extragenital lesions on skin or mucous membranes occur in about 25% of patients (range, 10%-30%), most often in the general area of the groin. A few patients develop lesions on one or more fingers, and herpes ocular keratitis sometimes occurs. About 20% are reported to show evidence of pharyngeal involvement, and about 50% have urethral involvement. Herpes simplex virus can be cultured from the cervix in 80%-90% of female patients. About 80% of all patients develop tender inguinal adenopathy in the second or third week.
Recurrent infection differs considerably from primary infection. Only about 5%-10% of patients experience systemic symptoms. Extragenital lesions appear in about 5%. Cervical culture is reported to detect HSV in less than 15%.
Neonatal HSV infection is usually due to HSV-2 associated with active maternal HSV-2 genital infection and is usually (but not always) acquired during birth rather than by transmission through the placenta. About 1% of pregnant women are estimated to have either overt or nonapparent HSV-2 infection. However, asymptomatic cervical or vulvar infection has itself been reported in about 1% (range, 0.5%-8.0%) of women. In genital HSV-2 infection during pregnancy only about 40% of infected women have typical lesions, and about 40% do not have visible lesions. It is estimated that if primary maternal HSV infection is present at delivery, there is a 40%-60% chance of symptomatic neonatal HSV-2 infection. If this occurs, there is serious or even fatal disease in about 50% of those infants. Delivery-infected infants do not develop symptoms until several days to 4 weeks after delivery. Symptoms may suggest sepsis or meningitis. If recurrent maternal HSV is present, there is only about a 5%-8% chance of infant infection. It is also reported that 70%-80% of neonatally infected infants are born to mothers who are asymptomatic at the time of delivery.
Diagnosis of herpes simplex infection culture.
Culture is still considered the gold standard HSV diagnosis. Material for culture must be inoculated into special transport media. Although some authorities advocate freezing the specimen, others report that refrigerator temperature is better for virus in transport media. Culture sensitivity depends on several factors. Some types of cells used for culture give better results than others. Specimens taken from vesicular lesions are considerably (50%-100%) more sensitive than material taken from ulcerative lesions, which, in turn, provide better results than crusted lesions. The earlier a lesion is cultured after it appears, the more likely it will yield a positive result (in one study, culture was positive in 70% of lesions less than 24 hours old, 50% in those 24-48 hours old, and 35% in those over 5 days old). A lesion from a primary infection is more likely to be positive than a lesion due to reinfection or recurrence. When urine or other secretions are cultured, the results from patients with primary infections are much more likely to be positive, since they shed virus much longer than patients with reinfection or recurrent disease. Culture in asymptomatic patients is much less likely to be positive than in patients with lesions. In addition to problems with sensitivity, specimens (in most hospitals) must be sent to a reference laboratory.
Antigen detection. Several methods are available to detect HSV antigen; most differentiate between HSV-1 and HSV-2 or claim to be specific for one or the other. Most have the advantage of same-day or overnight results. Some depend on abbreviated culture followed by use of specific antibody to HSV. Others (such as fluorescent immunoassay or latex agglutination) employ specific antibody on material from clinical specimens. To date, all methods have failed to consistently detect 95% or more patients who have positive results by standard culture and, in general, independent evaluations have not consistently upheld manufacturer’s claims. Some have achieved sensitivity in the 85%-95% range compared to culture; others have not. In general, whether the lesion is from primary or recurrent infection, the type of lesion and the number of days after the lesion appears before the specimen was obtained affects methods that detect HSV antigen similarly to culture. Sensitivity of direct antigen methods tends to be better in material from mucocutaneous vesicles than from genital lesions. Also, there have been problems in cross-reaction between HSV-1 and HSV-2, especially in fluorescent antibody methods. Some nucleic acid probe methods with PCR amplification have been reported to be equal to or better than culture in tissue or CSF.
Direct smear methods. The most rapid diagnosis is made through stained smears from scrapings obtained from a lesion. A sterile scalpel blade is used to unroof a vesicle and material from gentle scraping of the base of the lesion is smeared gently on a slide. Giemsa, Wright’s, or Papanicolaou stains can be used. For Giemsa or Wright’s stain, the smear is air-dried or fixed in methanol. For Papanicolaou, the smear is immediately fixed in cytology fixative. The slide preparation is sometimes called a Tzanck test. The technologist looks for multi-nucleated epithelial cells with enlarged atypical nuclei. The same findings are seen in varicella-zoster lesions. Pap stain also can show intranuclear inclusions. Sensitivity of the Tzanck test is reported to be 30%-91%, with average sensitivity probably about 45%-50%. It is probably less with persons who are inexperienced in obtaining specimens and interpreting the smears. Sensitivity is higher from vesicle scrapings than from other specimens. Fluorescent antibody tests have been applied to the smears, which increases positive results to about two thirds of cases.
Serologic tests for antibody. Most current methods are ELISA or fluorescent immunoassay plus a few LA kits. Antibody detection has also been somewhat disappointing. Acute and convalescent specimens must be obtained 2 weeks apart. A fourfold rise in titer is needed to prove recent onset of infection; this is most likely to be found in HSV-2 disease and during the time of primary infection (60%-70% of cases). Only about 5% of patients with recurrent HSV demonstrate a fourfold rise in titer. There may also be problems with interpretation due to the high rate of positive results in the general population and because of cross-reaction between HSV-1 and HSV-2 antibodies.
Other tests. In culture-proved HSV-1 encephalitis, one study reported that radionuclide brain scan revealed a focal lesion or lesions in the temporal lobe in 50% of cases, computerized tomography scan displayed some type of abnormality in 59%, and electroencephalogram (EEG) was abnormal in 81%. However, these procedures or their results cannot prove that the etiology is herpes infection. Spinal fluid tests show elevated CSF protein levels in about 80% of cases, increased WBC count in 97% (with about 75% of all cases between 50 and 500 WBCs/mm3), and normal glucose levels in 95% of cases. Another study found a normal cell count and protein level in 10% of cases on first spinal tap. Increase in WBC count is predominantly lymphocytic, although segmented neutrophils may be present in varying percentage (occasionally substantial) in the early stages. CSF immunofluorescent IgG antibody tests are about 25% sensitive by 10 days after onset of symptoms and about 85% after 15 days. At present, brain biopsy with culture of the specimen is the most accurate method of diagnosis. However, there is controversy about biopsy of such a vital organ. Culture of brain biopsy specimens is said to detect up to 95% of patients with HSV–1 encephalitis. Microscopic examination of the biopsy specimens can demonstrate encephalitis in about 85% of cases, but detects the intranuclear inclusions necessary to diagnosis HSV in only about 50% of cases. Use of immunofluorescent staining methods increases diagnosis to about 70%. Nucleic acid probe with PCR amplification was reported to detect over 95% of patients with HSV encephalitis testing CSF. However, homemade reagents were used. Clinical assessment alone is not sufficiently accurate: in one series of patients who underwent brain biopsy for suspected herpes, about 45% did not disclose herpes and about 10% were found to have treatable diseases other than herpes. CSF culture was positive in only about 5% of patients whose brain biopsy results were culture positive. In one large series, serologic tests suggested that 30% of patients had primary HSV infection and 70% had recurrent infection.
-
Human T-Cell Lymphotropic Virus I and II (HTLV-I and HTLV-II)
These are closely related retroviruses somewhat distantly related to HIV-1. Transmission is similar to that of HIV-1 (contaminated blood products, less frequently by sexual intercourse or breast feeding). HTLV-I is found predominantly in Southern Japan, some of the Caribbean islands, parts of Central and South America, and sub-Saharan Africa. HTLV-I has been detected in U.S. intravenous drug abusers (20%-25%; range 7%-49%) and female prostitutes (7%; range, 0-25%) and in Native Americans in the United States (1%-13%) and Central and South America (8%-33%). HTLV-I is associated with adult T-cell leukemia (also called T-cell leukemia/lymphoma), involving peripheral blood and lymph nodes with large malignant cells having a multilobated (monocyte-shaped) nucleus and having a short clinical course. HTLV-I is less frequently associated with a neurologic condition called tropical spastic paraparesis. HTLV-II currently has no definite disease association, although several have been suggested.
Serologic tests for HTLV-I antibody are mostly ELISA methods based on whole virus antigen. In general, these tests also detect most patients with HTLV-II. However, some reports indicate a significant number of HTLV-II patients are missed. Western blot methods are used to confirm and differentiate positive test results, and these procedures also have shown inconsistent results. Several new ELISA tests are based on several recombinant viral proteins and are said to reliably detect and differentiate the two viruses. At present, nucleic acid probe with PCR enhancement is the most sensitive and reliable way to differentiate HTLV-I and II.
Idiopathic CD4 T-cell lymphocytopenia (ICL)
This syndrome is being defined as CD4 T-cell counts below 300/mm3 (µL) or less than 20% of the total number of lymphocytes, no serologic evidence of HIV or HTLV infection, and no other known cause for CD4 depression. The main clinical findings are infection and other conditions associated with immunosuppression. Only a few cases have been reported as of 1994. Thus far, there has not been any strong evidence of blood-borne or sexual transmission. Retrovirus etiology has been suspected but not proven (to date).