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Results - Part B: Analysis of data by pathogen, continued

Herpesviruses

Viruses from the Herpesviridae family of DNA viruses, under surveillance through LabVISE, are herpesvirus type 6, cytomegalovirus (human herpesvirus 5), varicella-zoster virus (human herpesvirus 3) and Epstein-Barr virus (human herpesvirus 4). Total reports for these viruses to LabVISE between 1991 and 2000 are shown in Table 18.

Table 18. Laboratory reports to LabVISE of herpesviruses, 1991 to 2000

Virus	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	Total
Cytomegalovirus	1,820	1,728	1,561	1,727	1,404	1,373	1,017	766	1,220	1,312	13,928
Varicella-zoster virus	522	684	924	1,062	1,073	1,132	1,252	1,252	1,658	1,494	11,053
Epstein-Barr virus	1,361	1,625	1,570	1,516	1,887	2,084	2,151	1,903	2,196	1,926	18,219
Herpesvirus type 6	3	2	4	6	3	-	6	2	16	6	48

The major clinical syndromes associated with herpesviruses are summarised in Table 19.

Table 19. Major clinical syndromes associated with herpesviruses under surveillance in LabVISE, 1991 to 2000

Virus	Clinical syndrome(s)
Cytomegalovirus	Cytomegalic inclusion disease, CMV mononucleosis, significant infection in AIDS patients
Varicella-zoster virus	Chickenpox, shingles
Epstein-Barr virus	Infectious mononucleosis
Herpesvirus type   6	Roseola infantum, fever, otitis media, encephalitis

Cytomegalovirus

Cytomegalovirus laboratory reports were reported more frequently from males than females (male to female ratio 1.3:1). The largest numbers of notifications were found in children aged less than 5 years (27% of total reports, Figure 7).

Figure 7. Laboratory reports to LabVISE of cytomegalovirus infection, 1991 to 2000, by age and sex



Top of pageCytomegalovirus was identified in patients presenting with a wide range of diagnoses during the study period. Respiratory infections accounted for 48 per cent of diagnoses in which CMV were found. CMV was also isolated from blood (32%), nasopharyngeal swabs (25%), urine (14%) or diagnosed from serum (12%).

CMV infection in humans is common and life-long although disease is rare. Secondary activation of latent infections is common although disease caused by primary infection is more serious. There are two periods of increased transmission - during the perinatal period and in the reproductive years. Transmission may occur during birth, during breast-feeding and between infants in nurseries. Sexual transmission is also common. Congenital CMV infections occur in 0.5-2.2 per cent of all live births, mainly in primiparous mothers who were infected for the first time with CMV during pregnancy.¹⁸ Demographic and occupational factors also influence the risk of giving birth to an infant with congenital CMV infection.¹⁹ Symptoms occur in less than a quarter of infected children; however, those that are infected demonstrate cytomegalic inclusion disease, characterised by jaundice and multiple organ involvement. Congenital CMV infections are the leading cause of congenital malformations in the developed world. Clinical trials of treatment regimens for congenital CMV infections are under way.²⁰

There have been some profound changes in the epidemiology of CMV infections in children as a result of changes in breast-feeding and child rearing practices in Western countries over the past 15 years. In the USA, this has changed the prevalence of CMV among mothers and children in different socioeconomic classes. In middle and upper class households, which utilise child-care facilities, the exposure of mothers to CMV infection via their children will increase. In lower socioeconomic classes the relative decline in breast-feeding and the lower use of child-care facilities may increase the proportion of uninfected mothers.²¹

CMV infection by blood transfusion is common causing approximately 2.4 seroconversions per 100 units transfused.¹⁸ Organ transplant recipients are also susceptible to infection with CMV.

CMV infections are significant in HIV/AIDS particularly as a cause of retinitis. In advanced AIDS, CMV infection may cause mononeuropathy multiplex.²² Karposi's sarcoma in HIV positive patients was initially associated with CMV infection.²³ However, more recent work has identified a herpesvirus (human herpesvirus 8, Karposi's sarcoma associated herpesvirus, KSHV) as the etiologic agent of Karposi's sarcoma.²⁴

Varicella-zoster virus

Reports of varicella-zoster virus (VZV) to LabVISE increased over the study period and comprised 4 per cent of the total reports. In 2000, LabVISE reports of VZV totalled 1,494. There were slightly more reports from females than males (male to female ratio 0.9:1). Laboratory reports were from all age groups with the largest numbers of notifications found in the 25-29 year age group (9% of total, Figure 8).

Figure 8. Laboratory reports to LabVISE of varicella zoster-virus infection, 1991 to 2000, by age and sex



The great majority of diagnoses associated with identification of VZV were skin/mucous membrane disease (89.5%) and the virus was most commonly isolated from skin (69%) or blood (19%).

VZV causes an acute generalised viral disease in children commonly termed 'chickenpox', while reactivation of the virus in adults and the elderly causes shingles. More than 90 per cent of people are infected with VZV by adolescence. While most VZV infections cause mild disease in children, disease severity is greater in adults and case fatality rates can be 20 times higher (in the 5-9 years age group 1 death per 100,000 population compared with adults 1 death per 5,000 population).²⁴

While immunity is long lived, reactivation of the latent varicella infection is common in the elderly and up to 30 per cent of patients with shingles may suffer a post-shingles neuralgia.²⁴

A varicella vaccine has been available in the USA since 1995. This vaccine has an efficacy among children of between 70 and 90 per cent. In 2002, the Australian Technical Advisory Group on Immunisation (ATAGI) is considering this vaccine for inclusion in the childhood immunisation schedule.

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Epstein-Barr virus

Reports of Epstein-Barr virus (EBV) infection to LabVISE averaged 1,800 reports per year over the study period, about 7 per cent of total LabVISE reports between 1991 and 2000.

There were slightly more reports in females than males (male to female ratio 0.9:1). The largest numbers of notifications were in the 15 to 19 year age group (39% of the total, Figure 9).

Figure 9. Laboratory notifications of Epstein-Barr virus infection, 1991 to 2000, by age and sex



Over the study period, EBV was most often identified in patients presenting with reticuloendothelial disease (35%), and was most commonly isolated from blood (67%).

EBV causes an acute viral syndrome with fever, sore throat and lymphadenopathy accompanied by characteristic increases in the percentages of monocytes and lymphocytes (mononucleosis and lymphocytosis). The virus infects and transforms human B cells, although only 50 per cent of people infected will develop clinical infectious mononucleosis. While EBV infection is distributed worldwide, the peak of infection occurs in different age groups. Infection is more common among children in developing countries and more common among adolescents in developed countries. EBV is associated with the pathogenesis of Burkitt's lymphoma and nasopharyngeal carcinomas. Infection with EBV is possibly associated with Hodgkin's disease and non-Hodgkin's lymphomas particularly in HIV positive patients. Reactivation of latent EBV infection in HIV positive patients may cause interstitial pneumonia in infants and hairy leucoplakia and B-cell tumours in adults.²⁴

Herpesvirus type 6

Only 48 reports of herpesvirus type 6 (HHV-6) were made to LabVISE during the study period. HHV-6 is the cause of 'sixth disease', Roseola infantum, an acute febrile rash occurring in children aged under 4 years. HHV-6 can be an opportunistic infection in transplant recipients. A meta-analysis of studies between 1986 and 1996²⁵ concluded that between 38 and 60 per cent of bone marrow transplant recipients and 31-55 per cent of solid organ transplant recipients were infected with HHV-6 two to four weeks after transplantation. Bone marrow suppression, interstitial pneumonia and encephalitis were the most commonly reported clinical diseases associated with HHV-6 infection.

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Other DNA viruses

A number of other DNA viruses, reported to LabVISE in small numbers during the period 1991 to 2000, are shown in Table 20.

Table 20. Laboratory reports to LabVISE of other DNA viruses, 1991 to 2000

Virus	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	Total
Parvovirus	29	178	86	109	102	268	291	261	437	389	2,150
Papovavirus group	9	11	1	4	11	1	2	3	12	7	61
Molluscipox virus	21	10	8	4	3	7	5	2	15	11	86
Orf virus	5	7	4	2	1	1	9	6	8	7	50
Poxvirus group (not typed)	3	-	10	2	4	5	3	-	2	-	28

Among the parvoviruses, only parvovirus B19 is a known human pathogen.²⁶ Parvovirus causes prolonged epidemics of erythema infectiosum ('Fifth disease') among primary school aged children.²⁷ Fifth disease is a mild non-febrile illness characterised by a biphasic rash ('slapped cheek syndrome').²⁴ In Australia approximately 40 per cent of women are susceptible and around half of these are exposed to infection at home, typically via their school-aged children. Infection with parvovirus B19 in first half of pregnancy is associated with a 10 per cent excess foetal loss, anaemia and hydrops fetalis in 3 per cent. The overall risks of adverse events after occupational exposure to parvovirus B19 during pregnancy is low (excess foetal loss 2-6 per 1,000 pregnancies and foetal death from hydrops in 2-5/10,000 pregnancies.²⁷ It is recommended that susceptible pregnant women should be excluded from working with children during epidemics of parvovirus, which occur every 2 years and last for up to 2 years.²⁷

Parvovirus infections may cause severe chronic anaemia in the immunosuppressed.²⁴

Among reports of parvovirus to LabVISE, parvovirus was more commonly identified in women of childbearing age, possibly because of antenatal screening (Figure 10). The male to female ratio was 0.3:1, and 53 per cent of reports were in women aged between 15 and 45 years.

Figure 10. Laboratory reports to LabVISE of parvovirus infections, 1991 to 2000, by age and sex



The papovavirus group includes human papillomaviruses and polyomaviruses. Human papillomaviruses (HPV) are the causative organism of human warts. At least three types of cutaneous HPV are recognised - cutaneous, plantar and anogenital. Diagnoses of the latter have been increasing since the 1980s.²⁸ Polyomaviruses JC viruses cause a rare demylinating disease in the immunocompromised (progressive multifocal leukoencephalopathy). Polyomaviruses JC and BK virus infections are common in childhood and the virus persists in the kidney.

The poxvirus, molluscipoxvirus is the causative organism of the skin disease, molluscum contagiosum. Molluscum contagiosum skin papules occur on the abdomen, pubis, genitalia and inner thighs and persist without treatment for between 6 months and 2 years. The virus has not been isolated and serology is poorly defined. Transmission is by direct contact, including sexual, fomites and autoinoculation. Lesions may disseminate in HIV-infected persons.²⁹

The orf virus is another poxvirus and the cause of contagious pustular dermatitis, a proliferative cutaneous disease. The virus is transmitted to humans by contact with infected sheep and goats. The disease is worldwide in distribution, especially among farm workers, and has been reported as an important occupational disease in New Zealand.²⁴


This article was published in Communicable Diseases Intelligence Volume 26, No 3, September 2002