An outbreak of hepatitis A has been linked to berries sold at Costco. (Image credit: Getty Images)

I started my career at the U.S. Centers for Disease Control and Prevention as an outbreak investigator. So whenever there's an outbreak, I look carefully and ask, "What can we learn from this?"

In the case of the ongoing outbreak of hepatitis A linked to frozen berries sold by Costco, the answer is "plenty."

Hepatitis A is a viral infection of the liver with symptoms that include fever, fatigue, abdominal pain and jaundice - yellowing of the skin and eyes. It can be mild. But in some patients, the illness can last for months and lead to liver failure.

The infection usually stems from exposure to food handled by someone infected with the virus.

Woman Sues Costco Over Hepatitis A.

When an outbreak starts, there's a race to identify people who may have been exposed and give them treatment. Antibodies or a vaccine against the virus can prevent the illness if administered within two weeks after exposure. But in the case of the berries, at least 119 people have already become ill.

There are a couple of very interesting lessons to learn from this outbreak. First, our food supply is more global than you might think. According to the CDC, the berries in the implicated mix come from the U.S., Argentina, Chile and Turkey. The agency says the strain of hepatitis A causing this outbreak would be unusual in the Americas, so the problem berries or pomegranate seeds in this mix were likely imported.

Read about Dr. Besser's book, "Tell Me the Truth, Doctor."

Why is this important? Although the Food Safety and Modernization Act signed into law in January 2011 gave the U.S. Food and Drug Administration new authority to ensure the safety of imported foods, those provisions have not yet been implemented. There's very little inspection of foreign food growers and processors, and almost no inspection of imported foods themselves.

New rules governing imported foods can't be implemented until stricter rules are in place on domestic produce. Until then, we don't really inspect - we focus on early identification of outbreaks and then rapid control.

However, my biggest takeaway comes from looking at the characteristics of those who have become infected. The 119 people infected across seven states ranged in age from 2 to 84 years old, according to the CDC. Remarkably, only five people were younger than 18. That's very unusual.

It may be that fewer children eat berries, but I think the primary reason is prevention. In 2006, we began vaccinating all 1-year-olds against hepatitis A.

Learn about how vaccines aren't just for kids.

States that have historically had high rates of hepatitis A have been vaccinating longer and have also been providing catch-up vaccines for kids up to age 18. To date in this outbreak, none of the children who became ill had been vaccinated.

Dr. B's Bottom Line

On the policy front, we need to implement all the food protection measures Congress passed into law more than two years ago. These cost money, but if we want a safer food supply, we will have to pay for it.

On the prevention front, here's what you should do:

• Check your freezer to make sure you don't have any of the implicated frozen berries in there - hepatitis A survives freezing quite nicely;
• If you find one of the dangerous batches, throw it out;
• And think about getting the Hepatitis A vaccine, it works for all ages.

Hepatitis A is rampant in many parts of the world, so if you travel, the vaccine will provide protection. But as this outbreak shows, you don't need to leave your home to get exposed to viruses from other parts of the world. Who knows what the next culprit will be?

"Tell Me the Truth, Doctor" is a weekly column written by ABC News' chief health and medical editor Dr. Richard Besser. Look for Dr. Besser's book in stores now!