WHO关于HBV的文章，最后一句那位翻译一下。

错误日志

http://www.who.int/emc-documents/hepatitis/docs/whocdscsrlyo20022/introduction/how_is_hav_spread.html

How is HBV spread?
HBV is transmitted through percutaneous or parenteral contact with infected blood, body fluids, and by sexual intercourse.10, 11, 15, 23

HBV is able to remain on any surface it comes into contact with for about a week, e.g. table-tops, razor blades, blood stains, without losing infectivity.15, 31

HBV does not cross the skin or the mucous membrane barrier. Some break in this barrier, which can be minimal and insignificant, is required for transmission.31

HBV is a large virus and does not cross the placenta, hence it cannot infect the fetus unless there have been breaks in the maternal-fetal barrier, e.g. via amniocentesis. Still, pregnant women who are infected with HBV can transmit their disease to their babies at birth. If not vaccinated at birth, many of these babies develop lifelong HBV infections, and many develop liver failure or liver cancer later in life.23

Sexual intercourse with multiple partners or with persons who have multiple partners can be dangerous. One should not judge by appearance: most infected people look perfectly healthy and have no symptoms of disease, yet may be highly infectious.

All persons who are hepatitis B surface antigen (HBsAg) positive are potentially infectious. The many millions of people around the world who become HBV carriers are a constant source of new infections for those who have never contracted the virus.31

Blood is infective many weeks before the onset of the first symptoms and throughout the acute phase of the disease. The infectivity of chronically infected individuals varies from highly infectious (HBeAg positive) to often sparingly infectious (anti-HBe positive).

Hepatitis B is the only sexually transmitted infection for which there is a protective vaccine.23

最后一句是什么意思，不太懂。

moonshadow

Hepatitis B is the only sexually transmitted infection for which there is a protective vaccine.
B型肝炎是唯一有保护性疫苗的性途径传播的疾病。