nxious about anthrax? Scared about smallpox? Then consider this: a special strain of virus, born in the laboratory, that’s made up of equal parts Ebola and H.I.V. It may sound like the diabolical creation of terrorists, but in fact it’s the product of research at the University of Pennsylvania’s Institute for Human Gene Therapy. If scientists working there get their way, human patients will one day ingest these microbes as a way of curing genetic disorders.

The reasoning behind this idea is not as loopy as it may initially seem. What makes both Ebola and H.I.V. so lethal also happens to make them ideal candidates for doing the dirty work of cutting-edge gene therapy.

Say, for example, you suffer from a genetic disorder like cystic fibrosis – meaning that you lack the ability to produce a certain crucial protein. It may sound unimportant, but not having that one protein makes your lungs fill up with mucus to the point where you may die of respiratory infections. Enter gene therapy, which works by replacing flawed genes with fully functional genes. In the case of cystic fibrosis, the gene that can’t produce the protein is chopped out of each cell, and a working gene is put in its place. The cells can now produce the needed proteins. There’s no more mucus, and the lung problems disappear.

Repairing millions of diseased cells is a lot of work, however, and so scientists need an efficient corps of microscopic repairmen to cut and paste the genetic material. Viruses, which have a noted propensity for invading our cells and tinkering with our DNA, are perfect candidates for the job. Scientists can snip out the portion of the virus that makes us sick and replace it with healthy genetic code. In theory, this turns viruses – even harmful ones – into efficient cellular mechanics.

There’s only one problem: most garden-variety viruses are not especially aggressive, and the genetic material they introduce into cells rarely sticks. H.I.V., however, is notoriously invasive – and it has staying power inside the body. In theory, provided the toxic parts of the H.I.V. virus were stripped out and replaced with the healthy genes, the modified microbe could be injected into patients, where it would hang around, perpetually delivering and replacing genes to new generations of cells.

How does Ebola fit in? Ebola, it turns out, is particularly expert at invading the human respiratory system, where cystic fibrosis takes its toll. In an experiment published earlier this year, institute scientists reported how they extracted the lung-binding proteins from the Ebola virus, added a benign ‘‘marker gene’’ – the equivalent of a dress rehearsal for a therapeutic gene – and then slipped the whole package inside a hollowed-out version of H.I.V. The hybrid virus was then sprayed into the respiratory systems of mice, where it successfully delivered the marker gene.

A human version of this experiment would, obviously, be a little bit more complicated, not to mention dangerous. Purposely introducing viruses into patients, even viruses that have been neutered, is a risky proposition. Viruses can mutate or prompt deadly immune responses. Yet there’s something undeniably appealing about the idea of taming two of the most feared diseases; it’s a swords-into-plowshares feat of genetic engineering. And for now, the institute’s approach to gene therapy may be one of the best bets for curing debilitating genetic disorders like cystic fibrosis. Indeed, for someone whose lungs are literally drowning in mucus, the gamble of ingesting a kinder, gentler version of Ebola and H.I.V. may seem like a risk well worth taking.