Belinda Beresford
Tuberculosis and HIV are the ugly sisters of public health in South Africa. But hepatitis B gives as much cause for concern.
The endemic infection of hepatitis B has made sub-Saharan Africa one of the two global hot spots for liver cancer. The degree of primary liver cancer in sub-Saharan Africa is matched only by the Far East, where the hepatitis B virus is also the one predominantly wreaking the damage.
South African scientists are among the world leaders in hepatitis B research and in combating the virus the country could become an example of a public health success in Africa with every newborn child vaccinated against the disease.
Globally hepatitis and tobacco use are the leading causes of cancer. But while persuading people to give up smoking is a major problem, a good vaccination programme could curb hepatitis B.
On the face of it the hepatitis epidemic seems a disaster. Hepatitis B is 100 times more infectious than HIV and in sub-Saharan Africa it is so widespread that it is now endemic. Infection rates are estimated at 10% of the population, compared to less than 1% in Western countries. Infection with hepatitis B in the black population occurs mainly in early childhood. Between 80% and 90% of infected black children become chronically infected and of these one-quarter or more will get liver cancer.
In rural areas the infection rates are much higher. So are the dangers. A person with chronic hepatitis B is 100 times more likely to develop liver cancer than a non-infected person.
Liver cancer is almost invariably a death sentence. Virtually every person who develops the tumours dies within a year and most die within a few months. A liver transplant is usually unsuccessful because the cancer returns in the transplanted organ.
Michael Kew, professor of medicine at the University of the Witwatersrand, is internationally recognised as one of the leading researchers into hepatitis B. He says: “Hepatitis B and C are involved in more than 90% of liver cancers in the world and stopping them would go a long way towards eliminating liver cancer.”
Kew estimates that approximately 6% of the world’s population is chronically infected with one or the other virus.
While curing chronic hepatitis B is extremely difficult and expensive, preventing infection is quite easy. There is a vaccine for hepatitis B, which is now given to every newborn child in South Africa.
Taiwan started vaccinating babies in 1984 and within two years every newborn had been given the jab. The incidence of liver cancer in children there has been cut in half and, in the population as a whole, chronic hepatitis B infection is down to 1%, compared to 15% at the beginning of the campaign.
Children are the key to preventing the spread of the disease, because often people get infected as babies or children either from their mothers or from playmates. Children under five are highly infectious; this declines as they grow older. But, according to researchers at the University of the Witwatersrand three- and four-year-olds show almost the same levels of infection as adults.
Sub-Saharan Africa is fortunate in being afflicted predominately with the B rather than C virus. There is no vaccine for hepatitis C, which shows the same kind of mutability that makes developing a vaccine against HIV so difficult, and researchers don’t expect human trials of a hepatitis C vaccine to start for at least a decade.
But the connection between poverty and ill health is graphically demonstrated by the fact that in Africa only an estimated 5% of children are vaccinated against hepatitis B. South Africa is one of five countries that routinely do so many others can’t afford the cost of the shots.
The only way to treat the virus in chronic cases is to use interferon, an expensive drug developed from part of the human immune system. But even this is only successful in a small minority of cases.
Although scientists know that chronic hepatitis B infection often leads to liver cancer, the mechanism is still not definitely known.
Kew’s research suggests that one way the virus causes cancer is that the viral DNA becomes integrated into the human DNA of cells this integration has been found in about 90% of cases studied. One prevention strategy being studied here is gene therapy tailoring a piece of DNA to cut into the viral DNA so that it cannot produce cancer-causing proteins.
And other factors also come into play. South African scientists made a breakthrough showing that a mould, commonly found on staple crops in tropical Africa, can help trigger liver cancer.
The theory is that when processed by the body, by-products of the mould knock out a tumour-suppressing gene in human cells, allowing cancerous cells to proliferate without the immune system being alerted. This mould is widespread in Mozambique, which has the highest incidence of liver cancer in the world.
Kew points out that HIV and hepatitis B are “fellow travellers” often transmitted together incidence of hepatitis B and C is very high in prostitutes. Both can penetrate mucous membranes and infect through openings in the skin. But hepatitis B is the hardier of the two viruses it is not killed by antiseptics, for example.
Kew is confident. “At least we’ve found the causes. Now understand how it causes the cancer and how to intervene.”