The incidence of vertical transmission of hepatitis C virus

Mother-to-child transmission of hepatitis C virus

This review reinforces the lack of a single maternal risk factor that is highly associated with vertical transmission (VT) of the infection with hepatitis C virus (HCV): indeed HCV RNA levels, mode of delivery, breast feeding, viral genotype or maternal IL28B status were not associated with HCV VT.

Accuracy of HCV-RNA PCR tests for diagnosis or exclusion of vertically acquired HCV infection

The aim of the study was to estimate the sensitivity, specificity, positive (PPV) and negative (NPV) predictive values, and likelihood ratios for HCV-RNA PCR tests for the early diagnosis or exclusion of HCV infection in vertically exposed children. Data were included for children with confirmed HCV infection status from a European multi-center study. Confirmation was dependent on antibody status at or beyond 18 months, the 'gold standard' measure of infection status against which the use of qualitative HCV-RNA PCR tests was assessed. Of the 547 children included in this analysis, 193 were HCV-infected and 354 were not. Sensitivity of the HCV-RNA PCR test was low at birth (22%), but increased to 85% by 6 months. Specificity of RNA PCR was constant over age at 98%. The PPV of the PCR test rose from 33% at birth to 78% at 9 months of age, while NPV ranged from 96% to 99%. The high positive likelihood ratios from 1 month of age indicate strong evidence to diagnose infection but the negative likelihood ratios were consistent with weak evidence to exclude infection. The results suggest that the first qualitative HCV-RNA PCR test should be delayed until after the first month of life given the low sensitivity in the first few weeks. Although a negative test result after this time indicates probable absence of infection, this should be confirmed with a negative anti-HCV antibody test between 9 and 15 months of age as negative PCR results can be observed in infected children with fluctuations in viremia.

Hepatitis C: an epidemiological review

The aim of the study was to analyse the current literature regarding the mode of transmission of HCV and its global prevalence in different groups of people. A systematic review of the literature on the epidemiology of hepatitis C from 1991 to 2000 using computerized bibliographic databases which include Medline, Current Content and Embase. The prevalence of hepatitis C virus (HCV) varies tremendously in different parts of the world, with the highest incidence in the Eastern parts of the globe compared with the Western parts. Furthermore, certain groups of individuals such as intravenous drug users are at increased risk of acquiring this disease irrespective of the geographical location. Although the main route of transmission is via contaminated blood, curiously enough in up to 50% of the cases no recognizable transmission factor/route could be identified. Therefore, a number of other routes of transmission such as sexual or household exposure to infected contacts have been investigated with conflicting results. Hepatitis C infection is an important public health issue globally. Better understanding of routes of transmission will help to combat the spread of disease. In order to prevent a world wide epidemic of this disease, urgent measures are required to (i) develop a strategy to inform and educate the public regarding this disease and (ii) expedite the efforts to develop a vaccine.

[Hepatitis C and pregnancy]

PURPOSE

Today, the natural course of hepatitis C virus (HCV) infection during pregnancy and the prevalence of mother-to-child transmission are better known.

CURRENT KNOWLEDGE AND KEY POINTS

Antenatal screening for HCV infection needs to be proposed to women with risk factors. Viral replication needs to be confirmed by PCR in pregnant women with antibodies against HCV. To date, the clinical course of pregnancy and the mode of delivery have not been changed by HCV infection. Rates of vertical transmission of HCV are about 6% in women with HCV alone and 15% in women co-infected with HIV. A screening for HCV markers is required 18 months after delivery for infants born to HCV mothers. Because of the relatively low rate of HCV vertical transmission, pregnancy can be allowed in infected women. However, taking into account the efficacy of new antiviral strategies, treatment of HCV infection could be proposed before pregnancy.

FUTURE PROSPECTS AND PROJECTS

In case of HCV infection, a careful follow-up of both mother and newborns is required. Long-term follow-up of infected infants is needed to assess the consequences of perinatal HCV infection.

[Breastfeeding and hepatitis C virus (HCV): the need for a careful appraisal]

We review the available data on the possible role of breast-feeding in hepatitis C virus (HCV) transmission to infants of HCV-RNA-positive mothers. Current knowledge about HCV excretion through breast milk, HCV infection of breast-fed infants by mothers contaminated after delivery, and vertical transmission risk to infants breast-fed by chronic HCV viremic mothers are presented. Vertical transmission risk by breast-feeding HCV-RNA-positive mothers is unclear: no study has been performed with the aim and the required methodology to evaluate HCV transmission risk related to breast-feeding duration. Recommendations to HCV-RNA-positive mothers who wish to breast-feed their infant are discussed in light of present knowledge about HCV secretion in breast milk, mother-to-infant HCV transmission, and historical records on vertical transmission of other viruses to infants breast-fed by their viremic mothers.

Follow-up of transmission of hepatitis C to babies of human immunodeficiency virus-negative women: the role of breast-feeding in transmission

BACKGROUND

The studies on hepatitis C virus (HCV) vertical transmission, the effect of potential risk factors and the role of breast-feeding have reported conflicting results.

PATIENTS AND METHODS

Seventy-three infants of 63 anti-HCV-positive and anti-HIV-negative mothers were studied from 1993 to 1999 in the south of Spain. The mean period of follow-up in children was 29.2 +/- 19 months (range, 8 to 76 months); 6 (8%) children were lost to follow-up. Breast milk was studied for HCV-RNA in 68 samples of 35 mothers.

RESULTS

Alanine aminotransferase was high in 19 (26%) and HCV-RNA was positive in 46 (63%) pregnant woman. Breast milk HCV-RNA was negative in nonviremic mothers and positive in 20% of the viremic mothers. The overall rate of vertical HCV transmission was 11.9% (n = 8) (95% confidence interval, 6 to 23%) if HCV-RNA was positive one or more times, but only 1.5% (n = 1) (95% confidence interval, 0.1 to 9%) if HCV-RNA was permanently positive. Seven HCV-infected children did not develop antibodies to HCV, and they had a spontaneous clearance of the virus. A 10-month-old baby was HCV-RNA-positive from birth to the end of the follow-up. The genotype in each of the infants was consistent with that of their mother. The rate of HCV transmission was higher for infants of mothers with higher HCV viremia (P < 0.01) and also for infants whose mothers were HCV-RNA-positive in breast milk (P < 0.05). There were no statistically significant differences between other risk factors.

CONCLUSION

The presence of transitory viremia without seroconversion indicates that the vertical transmission of HCV is not important. This could be related to the viral charge and ingestion of milk of HCV-RNA-positive mothers. However, to advise avoidance of maternal breast feeding, it would be necessary to conduct larger studies.

Low risk of vertical transmission of hepatitis C virus by breast milk

To evaluate the risk of hepatitis C virus (HCV) transmission via breast milk, we collected 76 samples of breast milk from 73 chronically HCV-infected women and serum samples from their 76 perinatally HCV-exposed children. Enzyme immunoassay and strip immunoblot assay were used for detection of antibodies to HCV, and reverse transcriptase-polymerase chain reaction analysis was used for detection of HCV RNA. None of the 76 samples of breast milk contained HCV RNA, whereas 37 (59.7%) of 62 mothers tested for HCV RNA had HCV viremia. Only 1 of the 76 breast-fed infants had evidence of HCV infection. Because HCV infection in this child was detected 1 month after birth, it seems unlikely that it was transmitted by breast-feeding. These results indicate that HCV infection in pregnant women should not be a contra-indication for breast-feeding.

Hepatitis C--role of perinatal transmission

To evaluate the role of perinatal transmission in the spread of hepatitis C virus (HCV), we screened a cohort of pregnant intravenous drug using (IVDU) women for HCV antibody detection; where seropositive HCV RNA detection by polymerase chain reaction (PCR) was found we followed the infants longitudinally for HCV antibody and HCV RNA. Serum prevalence for HCV for this population was 80% with HCV RNA detected in 50%. Recruitment and follow-up over a 3-year period of a cohort of 83 seropositive women, their 91 newborns and 16 siblings of newborns, showed that there had been a 3% perinatal transmission rate with 1 sibling also infected. These positive cases were defined as transient in 1 case (HCV RNA positive by PCR at 1 month, but seronegative and HCV RNA negative at 10 months of age), 2 unevaluable (HCV RNA positive at 2 months of age, but patients lost to follow-up), and 1 chronic infection in a child at 34 months (positive HCV RNA and seropositive 34-month sibling). Maternal HCV RNA levels for those with infected infants was a mean 40-fold greater than those whose babies were uninfected, although this did not reach statistical significance. Of the remaining infants, the majority (93%) had lost passively acquired maternal antibodies by 9 months of age and all by 12 months. Of 18 women who were HCV seropositive and breast feeding (66% of whom were HCV RNA positive in their sera), none had detectable HCV RNA in breast milk. Hence we conclude that transmission of HCV from mother to infant appears to be of low frequency and positivity appears to correlate with maternal circulating viral load.

Role of breast-feeding in transmission of hepatitis C virus to infants of HCV-infected mothers

BACKGROUND/AIMS

The aim of this study was to explore the role of breast-feeding in transmission of hepatitis C virus (HCV) to infants of HCV-infected mothers.

METHODS

Sixty-five parturient asymptomatic carrier mothers with anti-HCV antibody (index patients) and 42 healthy parturient anti-HCV negative mothers (control subjects) were studied from September 1994 to June 1996. Maternal blood and colostrum were taken from each subject within 5 days post-partum and tested for anti-HCV and HCV RNA. Blood samples were collected from all infants at birth (cord blood) and at 1, 3, 6, 9 and 12 months of age. All infants were breast-fed. By 3 months post-partum, five of 65 index patients developed symptomatic liver disease and three of their infants developed acute viral hepatitis. Genotyping and subsequent nucleotide sequencing of the hepatitis C genome was done on these three symptomatic mother-baby pairs.

RESULTS

Within 5 days post-partum, the 65 carrier mothers had anti-HCV ranging from 1:40 to 1:30,000 and HCV-RNA ranging from 10(2) to 2.5x10(6) copies/ml. Both anti-HCV antibody and HCV-RNA were present in colostral samples but in significantly lower levels (p<0.0001). The five symptomatic mothers had anti-HCV titers ranging from 1:45,000 to 1:90,000 and HCV-RNA ranging from 2.5x10(8) to 4.5x10(9) copies/ml; three of their infants were symptomatic by 3 months of age. Hepatitis C virus genotype (3a) was concordant within each of the three mother-baby pairs, and all three pairs demonstrated greater than 97% homologies between pairs. These three infants were delivered by elective cesarean section at term, breast-fed regularly and there was no apparent maternal breast nipple trauma. None of the remaining infants had evidence of HCV infection up to 1 year of age. All 42 mother-infant pairs from the control group remained anti-HCV negative throughout this study.

CONCLUSION

Among asymptomatic mothers breast-feeding seems safe. Symptomatic women, especially with high viral loads, should not breast-feed to avoid the risk of viral transmission through breast-feeding.

Prevention of hepatitis C virus infection

Despite the promising progress made in the development of experimental HCV hyperimmune globulin preparations and recombinant vaccines, prevention of HCV infection will continue to be an important research front for many years. Until effective and safe immunoprophylaxis is available, preventive efforts will require further understanding of risk factors associated with infection and implementation of strategies to reduce such exposures.

Hepatitis C virus infection in pediatric patients

In contrast to our understanding of hepatitis C virus infection in adults, relatively little is known about the evolution and treatment of HCV infection in pediatric patients. Children at risk for HCV infection include recipients of multiple blood-product transfusions, organ transplantation and infants born to HCV-infected mothers. A proportion of HCV-infected pediatric patients do not have an identifiable risk factor. HCV infection is commonly detected in children previously presumed to have non-A, non-B hepatitis and cryptogenic liver disease. HCV infection usually leads to mild chronic liver disease in children but is also associated with chronic active hepatitis and cirrhosis. Interferon therapy is effective in a proportion of patients with chronic hepatitis C.

Use of polymerase chain reaction and antibody tests in the diagnosis of vertically transmitted hepatitis C virus infection

Data on patterns of polymerase chain reaction (PCR) and antibody test results in infants born to hepatitis C virus (HCV)-infected mothers were systematically reviewed to aid development of optimum testing schedules and diagnostic criteria for vertically exposed infants and to facilitate early identification of infected infants. Survival and cross-sectional analyses were used to estimate the timing of initial PCR positivity and subsequent PCR negativity in infected infants, and maternal antibody loss in uninfected infants was estimated as a weighted average of individual study findings. Of 74 eligible infants with strong evidence of HCV infection, an estimated 89% (90% confidence interval, 80-95%) were first PCR positive by 3 months of age, and less than 10% had subsequent PCR negativity attributable to intermittent viraemia or resolved infection in the first 18 months of life. The negative predictive value of PCR at 3 months of age was greater than 98% at an assumed rate of 5% vertical transmission, but as low as 88% at 25% transmission. The inclusion of 22 infants, each with a single PCR-positive result, increased the estimated frequency of resolved infections but made little difference to other estimates. A minority of PCR-positive infants had periods of antibody negativity by second- or third-generation assays, and among 297 uninfected infants, maternal antibody was not detected beyond 18 months. Thus, the majority of infected infants may be persistently PCR positive from 3 months of age, and the negative predictive value of PCR at 3 months is generally high. However, poor repeatability of PCR, inadequate infant follow-up, and inclusion of postnatally infected infants limits interpretation of the pooled data. Further studies using standardised PCR methodologies are needed.

The prevalence of HCV infection in a cohort of pregnant women, the related risk factors and the possibility of vertical transmission

The prevalence of antibodies for one or more HCV antigens was 2.3% of 1,347 mothers at childbirth. Compared with the principal factors studied, the presence of antibodies was more frequent in women who were carriers of HIV infection (3/3), in those who had suffered liver diseases (5/37) or who had had transfusion (3/25). This was as opposed to women who did not have any risk factor (p < 0.001). The prevalence of HCV-RNA was 1.3%; in relation to the antibody state, such a condition was more frequent in subjects with antibodies for 3 or 4 antigens (about 80%) compared with those who were positive for 1 or 2 antigens. HCV-RNA of the same genotype as the mother (type 1; 1a) was also found in the funicular blood of 2 of the 18 babies born to mothers who were positive for HCV-RNA. In the course of the follow-up (from the 3rd to the 18th month) the viral RNA was not found in any of the babies, nor was it found in the 2 who were positive at birth. Even the antibodies gradually disappeared, although slowly. At the 10th month, 91% of the babies resulted as having no antibodies and at the 18th month none of the babies resulted as having antibodies. Breast-feeding also appeared to have no influence on the transmission of the infection; out of 18 viremic mothers indeed 12 (67%) breast-fed their babies.

Hepatitis C virus RNA present in saliva but absent in breast-milk of the hepatitis C carrier mother

In order to examine whether saliva and breast-milk are mediators of the vertical transmission of hepatitis C virus (HCV) from an HCV carrier mother, serum, saliva, and breast-milk samples from 11 HCV carrier mothers were collected at the time of delivery, and at approximately 1- to 3-months intervals for as long as 30 months postpartum. Serum was also sampled from their children. All samples were analysed for the presence of HCV RNA, using the nested polymerase chain reaction method. No HCV RNA was detected in any breast-milk samples. In saliva, HCV RNA was detected in four of the 11 mothers (36%). These four mothers also had liver function abnormalities. Hepatitis C virus RNA was not detected in any serum samples of the children, and all children had normal liver function. The children were monitored for periods from 2 to 44 months. During this period, there was no evidence of virus transmission. Breast-milk is not likely to be a source of mother-to-child transmission of HCV. Maternal saliva may harbour HCV, but it may not result in infant infection.

Hepatitis C virus infection in pregnancy and the risk of mother-to-child transmission

The risk of vertical transmission of the hepatitis C virus (HCV) from infected mothers to their children during pregnancy and delivery was determined in 120 children born to HCV-positive mothers. Methods included enzyme immunoassay and immunoblot for detection of HCV antibodies and reverse transcription polymerase chain reaction (RT-PCR) for detection of viral RNA. Six (5%) children were perinatally infected with HCV as shown by RT-PCR. None of the infected children had clinical signs of hepatitis. None of the pregnancies was complicated by abortion, stillbirth, premature birth, or malformation of the child. Special concern was given to the possibility of HCV transmission via breast milk. In no breast milk sample obtained from 34 HCV-infected mothers was HCV RNA detected. These observations indicate that HCV infection is not necessarily a contraindication for breast-feeding.

Mode of hepatitis C virus infection, epidemiology, and chronicity rate in the general population and risk groups

Since the discovery of the hepatitis C virus (HCV), it has become evident that this infectious agent is a primary cause of posttransfusion and sporadic non-A, non-B hepatitis. Identification and introduction of surrogate markers for posttransfusion hepatitis and later introduction of anti-HCV screening has decreased the incidence of posttransfusion hepatitis. Community-acquired HCV infection is less common than posttransfusion HCV hepatitis. HCV infection may lead to liver cirrhosis without prior evidence of laboratory or histologic infection. Populations at risk for HCV infection include patients receiving organ transplants, health care workers, infants born to HCV-infected mothers, and hemodialysis patients. Intravenous drug abusers and their sexual partners also demonstrate a high rate of HCV infection. Nosocomial HCV transmission may occur despite the observance of universal precautions. Dental or surgical intervention, salivary inoculation, family members infected with HCV, cocaine abuse, HIV infection, and lower socioeconomic status also each correlate with an increased risk of infection. HCV infection is associated with many immune-mediated diseases. There may also be some relationship between human leukocyte antigens and HCV infection. Since there currently is no HCV vaccine, prevention of exposure remains the only possibility for reducing HCV transmission and prevalence.

Mother-to-child transmission of a hepatitis C virus variant with an insertional mutation in its hypervariable region

BACKGROUND/AIMS

We have analyzed the molecular basis of mother-to-child transmission of hepatitis C virus.

METHODS/RESULTS

Healthy pregnant women were screened for anti-HCV antibody and babies born to hepatitis C virus carrier mothers were prospectively investigated. Among the 35 pairs studied, the hepatitis C virus genome was detectable in only one baby, who did not show any significant symptoms of hepatitis. The viral load in the blood of the mother was one of the highest of the 35, and the population of the hepatitis C virus genome was heterogeneous. Furthermore, she was found to have a mixed infection with type 1a and type 1b hepatitis C virus. However, the hepatitis C virus genome obtained from the baby was only from type 1b, less heterogeneous and composed of the clones which were detected in the blood of the mother. The selected hepatitis C virus had a 12-nucleotide insertion in the amino-terminus of the E2 hypervariable region of the genome.

CONCLUSIONS

The incidence of mother-to-child transmission of hepatitis C virus from carrier mothers was shown by this prospective study to be low. The presence of selection pressure during transmission was suggested. The biological significance of the virus with 12-nucleotide insertion has to be determined.

Vertical transmission of hepatitis C virus: an epidemiological study on 2,980 pregnant women in Italy

The risk of mother-to-infant transmission of hepatitis C virus (HCV) varies according to the population studied and the tests used. Aim of the current study was to investigate HCV vertical transmission rate in children born to 30 HCV positive/HIV negative pregnant women in Italy. We investigated the potential vertical transmission of HCV by identifying HCV antibody seropositive pregnant women, by analyzing HCV-RNA in the peripheral blood using PCR and by prospectively following their offspring until 24 months of age. During the third trimester, 2,980 consecutive pregnant women were examined for anti-HCV antibodies by a second generation Enzyme-Linked Immunosorbent Assay (EIA2) and re-assayed by a second generation Recombinant Immunoblot Assay (RIBA2). A total of 32 mothers (1.07%) were positive for EIA2 test; 30 out of 32 had a reactive confirmatory RIBA2 test for HCV. All anti-HCV positive mothers were negative for HIV. These 30 mothers and their 30 babies formed the study cohort. Of the 30 anti-HCV positive mothers, 10 were also positive for serum HCV-RNA by PCR. All the babies born to the 30 anti-HCV positive mothers were initially negative for HCV-RNA (cord blood specimens), but three babies became positive at three months of age and remained positive thereafter. These babies had been born to 3 of the 10 mothers with viremia during the third trimester of pregnancy. These results suggest that HCV vertical transmission is possible in 10% of anti-HCV positives and in about 33% of the HCV-RNA seropositive mothers.

Vertical transmission of hepatitis C virus infection

Vertical transmission of hepatitis C virus (HCV) was studied in 58 infants of 55 mothers (3 sets of twins). HCV RNA analyses by the polymerase chain reaction (PCR) and alanine aminotransferase (ALT) were performed on consecutive blood samples from birth to 18 months of age (0, 3, 9 and 18 months). Data on factors possibly influencing mother-to-infant transmission of HCV, such as concomitant human immunodeficiency virus (HIV) and hepatitis B virus infection during pregnancy, maternal HCV RNA status at delivery, mode of delivery, prematurity and breastfeeding habits were collected. In addition, 6 older siblings (age 4-10 years) of the infants were tested once for anti-HCV. Of the 55 mothers 52 (95%) had a history of intravenous drug use (IVDU). Two mothers were HIV positive. 40/54 (75%) tested mothers were HCV RNA positive. 16 (27%) infants were delivered by Caesarean section, and 50 (86%) infants were breastfed. All infants were HCV RNA negative on all occasions and anti-HCV negative at the age of 18 months. Maternally acquired anti-HCV antibodies disappeared and were not detected by 9 months in 78%. One of the 6 older siblings was anti-HCV and HCV RNA positive. We conclude that the risk of vertical HCV transmission is low in infants of HCV-positive/HIV-negative mothers, and that breastfeeding seems to be safe in this group.

Vertical transmission of hepatitis C virus infection

Since the virus responsible for non-A, non-B hepatitis was cloned in 1989, much has been learnt about the epidemiology, diagnosis and clinical spectrum of hepatitis C virus (HCV) infection. As the routes of transmission are elucidated, specific groups of children as well as adults are known to be at particular risk of infection. The women most at risk of HCV infection are those with a history of injecting drug use. Mother-to-child transmission has been documented, although the exact risk has not been quantified, and the factors influencing the risk remain to be evaluated. This article reviews current knowledge on vertical transmission of HCV, and provides some guidelines on the management of infants born to women infected with the virus.