WHY would God create something, or perhaps allow something to evolve, which causes such distress and suffering? I would argue: because viruses have a positive part to play in nature, and their ability to harm humans is a side effect of this.

Viruses are non-living entities that depend on their ability to hijack other cells to replicate. On their own, they cannot do the things that living beings do: grow, change, reproduce.

There are billions of types of virus out there: most of them are bacteriophages, which infect bacteria. So, why did God make viruses?

Bacteria and viruses are essential for life on earth; there are billions of types of bacteria, many of which can take inorganic compounds and turn them into a form that living things can use. But the compounds are trapped inside the bacterial cell. The bacteriophage viruses attack the bacteria, splitting them open and releasing these nutrients.

Bacteriophage viruses are also important in controlling the bacteria population. Bacteria divide into two every 20 minutes: unchecked, the earth would be filled with bacteria; so the ’phages are part of God’s balanced ecosystem.

Now that we can look at DNA in detail, we can see that many types of plant and animal have viruses in them. Often, the viruses are helping the plant or animal: for example, viral-infected mice are more resistant to some bacteria. All of us have viruses living in us, along with many types of bacteria — in our gut and on our skin — which are important for our continuing health.

Many of the viruses that cause human disease originated in another species, and crossed the species barrier: HIV seems to have come from a Simian (monkey) virus, and SARS from bats.

Some viruses that cause illness in humans were probably in a balanced symbiotic relationship with their intended host.

Viruses can be used by scientists in a positive, redemptive way. Our understanding of genetics, of how cells work, and how we can alter DNA and cells’ machinery are possible only because of viruses. Genetic testing and genetic treatments rely on viruses that cut DNA strands in precise places.

Viruses are a natural part of God’s good creation, and are important in cycles of death and decay, a tiny percentage of which can cause human disease.

The Revd Dr Alison J. Gray is Priest Associate at the Ascension, Munich, and a formal medical doctor. She chairs the Royal College of Psychiatrists’ spirituality and psychiatry special-interest group.