Viruses are sneaky-smart opportunists with an eye for the long view.

So suggests a new study — conducted by a team of scientists including Katie Barott, a postdoctoral researcher at the University of Hawaii at Manoa’s Hawaii Institute of Marine Biology — that appears in the latest edition of the science journal Nature.

The researchers conducted a series of experiments that put to the test two competing theories of how viruses respond to microbial growth in and around coral reefs. The results, they said, could lead to not just a better understanding of how microbes affect the health of coral reefs, but also to possible improvements in the treatment of conditions like cystic fibrosis.

Traditional understanding held that as microbes increased in an ecosystem, so did the number of viruses, thereby keeping the microbial population in check — the so-called “kill the winner” theory.

“Kill-the-winner seems to make sense,” said lead author Ben Knowles of San Diego State University in a news release. “The logic behind it has been around for a while. The reasoning is very seductive.”

Seductive, perhaps, but not necessarily true in every circumstance.

The researchers collected samples of microbe-rich seawater near coral reefs in the Pacific and Atlantic oceans and subjected them to a combination of microscopic and genomic techniques.

Surprisingly, the researchers found that as microbial abundance increased, the virus-to-microbe ratio significantly decreased.

The team then incubated seawater from a pristine coral reef and from Mission Bay in San Diego and monitored the viral and microbial abundance over several days. Again, the virus-to-microbe remained low despite an increase in microbes.

Finally, the researchers looked to see whether the viruses they were examining exhibited virulent, predatory traits. What they observed, however, was that viral communities became less virulent as the microbe count increased.

The research thus suggested that rather than adhering to a “kill the winner” reaction to microbial growth, viruses drawn from coral reefs reacted in a “piggyback the winner” manner, integrating themselves into their host, replicating more slowly than normal and avoiding both competition with other viruses and conflict with the host’s immunity defenses.

“When you have a fast-growing host, if you’re a virus, you profit more from integration,” Knowles explained. “It’s just intelligent parasitism.”