Ocean Watch

Two weeks ago a 34-year-old man fell into the Ala Wai Boat Harbor, got an infection and died a few days later.

Oliver Johnson's death shocked the community. Sure, we knew Ala Wai water wasn't exactly pristine, but countless people, me included, have been jumping and falling into that harbor for years with no ill effects. What happened?

The natural assumption is that sewage did it. As a result of heavy rain days earlier, the city diverted millions of gallons of sewage from a broken pipe into the Ala Wai Canal.

Sound science, however, does not assume anything. This case has more factors to consider than a sewage mess.

The bacterium that caused the man's death is called Vibrio vulnificus. It and its family members can cause skin infections, blood poisoning and diarrhea, including cholera.

Since cholera and deadly infections are rare in this country, you'd think Vibrio bugs would be rare, too. Not so. Vibrios are among the most common naturally occurring bacteria in waters worldwide. These bacteria are found in fresh, salt, brackish, pristine and polluted water. The germs also live inside the mouths of fish and the shells of invertebrates.

Of the Vibrio family, vulnificus is the most lethal and most puzzling. It's only been recognized since 1976, and the first case of disease from it was diagnosed in 1979.

Currently, researchers have discovered more than 100 strains of vulnificus and think thousands more could exist. (A strain is the same species but differs by some minor trait.) Not all the strains make us sick. Why some do isn't known and is the subject of intense study.

A related research topic is how Vibrio vulnificus responds to stress. When conditions change, some plants and animals produce what are called heat shock proteins, which help the organism adapt.

The rush of rain into the harbor, for instance, changes its salinity. Sewage increases its nutrients. Global warming is changing its temperature. And who knows what washed in there from our streets?

Some or all of these factors could trigger a survival response in vulnificus that makes it more, or perhaps less, virulent to people and aquatic animals. It's not clear.

What is clear, though, is that most of these environmental changes have been man-made, including the harbor itself.

Most people in the U.S. get Vibrio vulnificus blood poisoning from eating raw oysters bearing these nasty germs. Here in Hawaii, though, Vibrio germs usually get into the bloodstream through a cut or even a tiny scrape.

Like most pathogens, the severity of a vulnificus infection depends on the strength of the germ and susceptibility of the person. Those with diabetes, liver disease or other immune-related illnesses can't fight vulnificus well and often quickly lose the battle.

We might never know all the answers to Johnson's tragic death, but one thing we do know: When humans mess with nature, the results are rarely good.