Mail & Guardian (Johannesburg) - October 31, 2006
Belinda Beresford

Mother-to-child transmission of HIV has been found to be almost 50% higher when the woman smokes.

The American Journal of Public Health reported earlier this year that the average immune strength of HIV-positive people starting ART -- measured by the CD4 cell count -- improved less among smokers than among non-smokers.

The study found smokers tend to have higher viral loads and develop Aids-related illnesses faster.

Research in 2003 found smoking doubles an HIV-positive woman's chance of developing pneumonia and weakens the impact of ART by 40%.

Charles Feldman, chief physician at Johannesburg Hospital and head of pulmonology, commented: "When a person is exposed to HIV, the immune system can protect against infection. But smoking affects the whole defence mechanism, as immune cells become dysfunctional."

Feldman says there is evidence that smoking can increase the impact of acute HIV infection -- the initial few weeks when the body tries to respond to the new invader. There is evidence that the damage inflicted on the immune system by initial infection influences the longer-term health and survival of the infected person -- and that smoking may exacerbate the damage.

"Preventing people from starting to smoke and by helping those already hooked to stop, is one tool for managing the HIV epidemic, potentially a simple and cost-effective one," says Feldman.

Smokers tend to get more colds and pneumonia, and are doubly at risk of contracting flu. This is because cigarette smoke knocks out the respiratory system's first line of defence: hair-like structures in the lungs called cilia, which expel invasive substances.

The toxins in cigarette smoke also damage pulmonary immune cells and increase the chances of macrophages being invaded by HIV.

The lungs, with the total surface area of a tennis court, are considered a far more effective distributor of substances through the body than a hypodermic needle. Toxins in cigarette smoke increase the risk not just of lung cancer but of other tumours, including cervical cancer and Kaposi's sarcoma.

Smoking stimulates the production and activity of immune cells called "neutrophils", which wage chemical warfare against pathogens through free radicals. Excessive stimulation of neutrophils means higher levels of free radicals in the body, causing oxidative stress, tissue damage, ageing and higher cancer risk.

The National Council Against Smoking estimates that 5,35-million people in South Africa smoke, or 22% of people aged over 15.

Some experts suggest that alcohol may partly explain the link between smoking and HIV. Smokers may be more prone to drink and thus more likely to have unprotected sex.

But scientists believe other social factors may underpin the connection. People who smoke tend to be poorer and less educated -- and thus less likely to heed, understand or act on safe-sex messages.

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