HBV transmission

transmission HBV
4 Oct 2017
H3
Organisms such as hepatitis B virus (HBV) that cause infections
via sexual transmission can also cause infections
via other routes, such as percutaneous transmission by
contaminated needles and vertical transmission in utero or
during delivery. As a typical STI, HBV infection is present in
all types of populations. Sexual contact and vertical transmission
from mother to infant are responsible for the large
majority of HBV infections worldwide [4].
HBV infection as an STI is well documented. It is mainly
common among men who have sex with men (MSM), because
multiple partners are common in this population;
and anal sex is usually more traumatic than vaginal intercourse,
resulting in increased risk of exposure to blood [4,
5]. HBV infection is also extremely common among heterosexual
individuals who have multiple sex partners or contact
with sex workers [6].
HBV transmission has been found to occur through
various forms of human contact, including vertical transmission
from mother to newborn, sexual contact, close
household contact, needle sharing, and occupational
(healthcare) exposure (horizontal transmission)
H3
Similarly, the presence of antibodies against hepatitis B e antigen or antibodies against Hepatitis B core antigen at birth or up to 2 years of age is simply due to their crossing the placenta from the mother to the fetus, and therefore is unrelated to infection.
H5
since HBV DNA can be detected in breast milk and breast lesions may increase exposure of infants to HBV.
Under the recommended prophylaxis, breastfeeding is not a risk factor for mother-to-child transmission of HBV. Therefore,
clinicians should encourage HBV-infected mothers to breastfeed their infants.
That breastfeeding does not add risk for the mother-to-child transmission of HBV .
Thus, we further compared the infection rate in 137 children born to HBeAg positive mothers. Of them, 63 were breastfed
and 74 were formula-fed; their mothers had similar HBV DNA levels (breastfed 2.32×10 vs. formula-fed 2.47×10 IU/ml, P = 0.613).
Breast- and formula-fed infants had comparable prevalence of HBsAg (6/63, 9.5% vs. 7/74, 9.5%, P = 0.990) and of anti-HBcpositive/
HBsAg-negative (7.9% vs. 10.8%, P = 0.567).
Before the availability of HBIG and hepatitis B vaccine, Beasley et al [10] reported a cohort of 92 breastfed babies and 55 nonbreastfed
babies, whose mothers were HBsAg-positive during and after delivery. When the infants were tested at 3 or more months
old, with a mean follow-up period of 11 months, no significant difference was found in the acquisition rate of HBsAg (49% vs. 53%)
or anti-HBs between the two groups. These results demonstrated no correlation between breastfeeding and the development of
HBV infection in children of carrier mothers.
H10
HBV is transmissible not just among
humans but also in the great ape,  including the chimpanzee,which was used until recently as an
experimental model. HBVcanalsoinfectthemacaque(Macaca
fascicularis)(Dupinayetal.,2013) and,inalaboratorysetting,thetree
shrew(Tupaiabelangeri)(Walteretal.,1996).

1. sexualH3
   HBV is efficiently transmitted by sexual contact [10].
   The primary risk factors are unprotected sex with an HBVinfected
   partner, mainly unvaccinated MSM and heterosexual
   individuals with multiple sex partners or contact
   with sex workers [6]. MSM have long been known to have
   high rates of STIs
   Heterosexual transmission is still important, as shown
   by the 40% transmission rate to nonimmune partners of
   patients with acute HBV hepatitis or chronic HBV infection
2. maternalH4
   In highly endemic countries, mother-to-child transmission accounts for most cases of infections and is, therefore, the main mechanism that perpetuates the infection in the population
   there is a residual risk of vertical transmission – namely, about 3%.
   Indeed, a maternal viral load below 106 IU/mL is not associated with vertical transmission,30 whereas the risk of transmission is about 3% in cases of a maternal viral load 106–107 copies/mL, about 7% for a viral load 107–108 copies/mL, and about 8% for a viral load .108 copies/mL.
   However, breastfeeding is not a risk factor for HBV infection.
   
   1. risk of transmissionH4
      Without prophylaxis, the risk of HBV vertical transmission is high. The risk is highest in HBsAg- and HBeAg-positive mothers (transmission rate: 70%–90%), and low for HBsAg-positive HBeAg-negative mothers (transmission rate: 10%–40%).
   2. routeH4
      Mother-to-child transmission of HBV can occur via three modalities: intrauterine transmission; transmission during delivery; and postpartum transmission.
      
      1. intrauterine transmissionH3
         Intrauterine transmission accounts for only a minority of cases of HBV transmission.21,32 In fact, a Chinese study showed an intrauterine infection rate of 3.7% in a sample of 402 newborn infants of HBsAg-positive mothers.32 A high viral load and positivity of HBeAg were factors associated with an increased risk of transmission through this route.32 Intrauterine transmission can occur in two ways: HBV can reach the fetus by crossing the placental barrier; and during its passage, HBV can infect and replicate in all types of placental cells before it reaches the fetus.32–34 It is noteworthy that the percent of infected cells decreases from the maternal side (43.6%) to the fetus side (18.8%) of the placenta.32 Finally, HBV may reach the fetus through transplacental leakage of the maternal blood into fetal circulation, a condition that is associated with prolonged threatened preterm labor or threatened abortion due to increased uterine contractions.
         it is feasible that the placenta acts as a filter that is crossed only in case of a high maternal viral load.
      2. during deliveryH4
         Transmission of HBV during delivery is the most frequent method of vertical transmission. It is mostly due to newborn contact with the mother’s infected secretions or blood at the time of delivery.
      3. After birthH4
         A proportion of babies (as high as 34%) may acquire infection after birth due to close contact with the mother.22 However, breastfeeding is not a risk factor for HBV infection
3. blood
   1. Hemodialisis patientH12
      Patients on maintenance HD are among the group
      at highest risk for HBV infection. Most HBV infection
      outbreaks in patients in HD units are caused by
      cross-contamination via the following factors: (1)
      environmental surfaces, supplies (e.g., hemostats and
      clamps), or equipment that is not routinely disinfected
      after each use; (2) multiple dose medication vials and
      intravenous solutions that are not used exclusively
      for one patient; (3) medications for injection that
      are prepared in areas adjacent to areas where blood
      samples are handled; and (4) staff members who simultaneously
      care for both HBV-infected and susceptible
      patients.
      A study in 2003 in Manitoba,
      Canada, showed that 0.8% of HD patients were
      positive for the HBsAg.
      Several studies have also been performed
      in Indonesia. In a study conducted in West Java, the
      rates of HBsAg and anti-hepatitis C virus (anti-HCV)
      seropositivity among HD patients were 6.8% and
      73.5%, respectively[73], whereas those in Yogyakarta
      were 7% and 81%, respectively[74]. After almost 20
      years, more recent data on the rates of infection in
      Yogyakarta showed 11.2% seropositivity for HBsAg
      and 80.7% for anti-HCV. Our previous studies in
      Surabaya showed that the anti-HCV prevalence was
      between 76.3% and 88%.
      there is a
      strong possibility that the prevalence of HBV and/or
      HCV infections among HD patients is caused by
      nosocomial infections.