The Virus in You

Environments like these are multiplying all over the world as the population increases and we encroach on habitats that were once isolated from humans. That is giving rise to a disturbing trend: viruses that once lived apart from humans, in animals like monkeys, are mutating and crossing the species barrier. This occurred in 1999 in Malaysia when the Nipah virus, which triggers encephalitis and respiratory illnesses, first emerged in humans. Previously the virus had been only found in fruit bats, but as humans began building farms in remote areas where the bats lived, the virus spread to pigs and ultimately humans. Before it was contained, more than 100 people died and nearly one million pigs were destroyed.

Similarly, the practice of eating bush meat in many African countries has exposed hunters and their families to bacteria and viruses normally contained within the animal population. One of the most deadly to cross into the human population is the Marburg virus, a severe form of hemorrhagic fever closely related to the Ebola virus. Victims bleed to death, often from every orifice. Researchers have made strides with a test vaccine against Marburg in monkeys, but a vaccine for humans is not yet available.

People living with exotic pets have also unwittingly helped bring viruses from the animal to the human world. In 2003 a shipment of rats that was infected with the monkeypox virus was imported to Chicago from Gambia in West Africa. The rats infected other rodents in a pet store, and by the summer of that year thirty-five cases of monkeypox in humans had been identified in six midwestern states — the first confirmed cases of the disease in humans in North America. Fortunately, they were stricken with a weak form of the virus and none died.

The emergence of new viruses is accelerating — but are they actually becoming more dangerous? The answer is both yes and no. In cases such as hiv, the virus spreads rapidly because humans have no immunity. In other instances diseases appear to be more dangerous than they really are because we do not have methods to treat them. Bacterial infections acquired in hospitals, for example, are growing increasingly resistant to normal antibiotics. But the bacteria are not any more capable of causing disease than they were; it is simply that they have mutated and we cannot treat them. A similar problem is occurring with anti-malarial drugs, which are no longer as effective as they once were.

In the end, perhaps the biggest reason why viruses are mutating across species barriers and killing more people today than thirty years ago might be because the body’s natural ability to fight infections has decreased in a significant proportion of the human population that is already chronically infected with diseases such as tuberculosis. The best-known is hiv, which has infected over 40 million people worldwide. Add to that the fact that the population of many countries is aging and thus is increasingly vulnerable to attacks by viruses. Is it any wonder that many scientists believe it is inevitable that mutating viruses will soon trigger a pandemic?

The only way to stop a pandemic is to develop vaccines and antimicrobial drugs as quickly as threats emerge. But that may not be possible because it takes ten to fifteen years to develop and fully test a vaccine — far longer than the time it would take a pandemic to sweep the world.

In the long run, a solution may be found in an emerging field of science known as pathogenomics. Scientists working at the Vaccine and Infectious Disease Organization (vido) at the University of Saskatchewan are at the forefront of this field. Their goal is to find a way to stimulate and boost the ability of the human immune system to fight infectious organisms before they take hold. In some people this will occur naturally, but in others the response is slower. Researchers at vido are conducting experiments that may trigger a quicker immune response in such people. They are attempting to develop a peptide (a protein) or synthetic dna that, when injected, is recognized by the body as foreign, triggering the individual’s immune system to kick in. They are also trying to answer a fundamental question: how do viruses interact with humans at the genetic level to cause disease? Until science can find the answer to that mystery, we will be unable to prevent viruses from jumping the barrier between animals and humans.