Column: What denial?

When you think of how science is supposed to work, what do you imagine?

It’s not all lasers and collecting animals — what people think of as the fun, exciting stuff. It can be about that, of course, but it’s not the most important part.

Science is about thinking critically. It’s about finding the closest approximation to the truth that we can, given the fact that we can’t possibly know everything.

This column is the result of a phone call to The California Aggie office from a highly intelligent man reaching out to me, trying to convince me of something that is very important to him.

Unfortunately, highly intelligent doesn’t necessarily mean correct.

Mark Harris called to inform me about a report released by UC Berkeley professor Peter Duesberg. The study purports to show that there is no AIDS epidemic in South Africa.

In fact, Duesberg thinks that AIDS is not caused by HIV at all.

Despite the overwhelming scientific consensus that the Human Immunodeficiency Virus (HIV) causes Acquired Immune Deficiency Syndrome (AIDS), there is a small but somewhat vocal minority of people — some scientists, some laymen — who claim that AIDS has other causes. The most common alternative that I was able to find was that AIDS is in fact caused by the use of recreational drugs, or even by the AIDS treatment AZT.

First, a (very) brief overview of HIV/AIDS. When a person is infected with HIV via bodily fluid contact with an infected person’s bodily fluid (either blood or semen), the virus goes into the blood stream until it attaches to an immune cell called a Helper T-cell, whose normal job in the body is to activate and direct immune cells to infections. The virus may lie dormant for years until something (we still don’t know exactly what) activates it to divide and kill the immune system. The person becomes much more susceptible to infections and cancers that a healthy immune system could easily fight off.

There are two factors to this thought that HIV does not cause AIDS: the scientific arguments themselves and the logic behind the arguments. However, lacking the room in this single column to address all the evidence (as I wish I could do here), I will focus on just one, as an example of how people can go astray.

Let’s start with an easy one. In my conversation with Harris, one piece of evidence that he said was counter to HIV causing AIDS was the fact that HIV does not infect chimpanzees, despite humans’ close genetic and physical similarities to chimpanzees.

It’s true that HIV does not infect chimpanzees, as one can figure out from the name of the virus itself. What is true is that chimpanzees and other primates have a very similar version of the virus that does infect them, called the Simian Immunodeficiency Virus, or SIV. Over the thousands of years, they have co-evolved with this virus, the resulting illness has lessened. However, when a mutated variant occurs that does cause illness, the infection does result in AIDS.

The reason HIV doesn’t infect other primates is because every virus has a receptor site that is specific to the cell that it wants to infect. The one percent or so of genetic difference between us and chimpanzees is enough to cause variation in receptor sites of body cells; for HIV, this means that a chimpanzee immune cell is too different from a human immune cell to be infected.

His argument here, that HIV is unlikely to cause AIDS in humans because HIV doesn’t cause illness in our closest relatives, chimpanzees, is an example of a non sequitur. This is a logical fallacy that means the person was using an unrelated fact to try to prove that his claim was true. As you can see above, it doesn’t work.

But why am I spending so much time on this? Experts have written whole books on the subject, giving a great deal more detail than I have room for in this single column, debunking each denialist point. Why?

It’s because HIV denial has real-life consequences, as some African leaders, in countries where infection and transmission is incredibly high and treatments difficult to afford, claim that treatments for HIV cause AIDS rather than help them. They delay treatment programs, leaving people to sicken and die.

Only a very small minority of people think HIV does not cause AIDS, but they have a loud voice. When such a health pandemic is at stake, scientists cannot be afraid to be louder.

AMY STEWART can be reached at science@theaggie.org.