At least 14 Californians -- including two people in the Bay Area -- have been infected in an outbreak of hepatitis A connected to frozen berries, and that number will almost definitely increase in the coming days and weeks, public health officials say.
But there's one group of people unlikely to get sick: kids. That's because most of them are vaccinated against hepatitis A.
A vaccine to prevent infection was developed in 1995, and federal guidelines recommend all U.S. children get vaccinated by age 2. In California, the hepatitis A vaccine is not required for school entry, but about three-quarters of children have been immunized by age 3.
Since the vaccine offers decades, and possibly even a lifetime, of protection against hepatitis A, those kids are all safe from the virus that may be contaminating their homemade berry smoothies. Instead, it's their parents and grandparents who are getting sick.
"What we've seen with these cases is they're almost all adults so far," said Dr. James Watt, chief of the Division of Communicable Disease Control for the California Department of Public Health.
As of Wednesday, there were at least 49 cases of hepatitis A in the United States associated with the outbreak, according to the Centers for Disease Control and Prevention. Almost all of those cases are in adults.
The two Bay Area cases -- in Contra Costa and Santa Clara counties -- involved women, ages 62 and 22. Both were hospitalized in May and are now recovering.
Hepatitis A is a virus spread through contaminated water or food that causes inflammation of the liver. Most people recover from it without serious illness or long-term consequences, but it can be very serious, even fatal, in some patients. In rare cases, patients may need a liver transplant.
Symptoms of infection include diarrhea, dark urine, fever, headache, nausea and abdominal pain. Patients may develop jaundice. Symptoms typically show up two weeks to two months after exposure.
Children are less likely than adults to experience symptoms, for reasons that doctors don't fully understand. But that means children often can be infected and not know it, making them reservoirs of disease that can be passed on to their parents or other adults around them.
"That's one of the challenges -- in children, 80 percent of them with hepatitis A will have no symptoms whatsoever," said Dr. Tomas Aragon, health officer for the San Francisco Public Health Department. "Adults will get exposed to it from children and never even know it. About half the cases we see, you can't figure out where they got it."
The current outbreak is under investigation by the U.S. Food and Drug Administration. It involves a specific product -- Townsend Farms Organic Antioxidant Blend frozen berry and pomegranate seed mix -- that was mostly sold at Costco stores.
On Tuesday, Townsend Farms, the Oregon company that produces the fruit, voluntarily recalled the product. Anyone who already has eaten the berries should contact a doctor; unused fruit should be thrown away.
The berries came from a variety of sources both in the United States and abroad, but the investigation is focused on the pomegranate seeds, which came from Turkey. Early laboratory studies show that the strain of hepatitis A currently circulating is the same strain that was part of an outbreak in Europe last year, one that typically is found only in North Africa and the Middle East, according to the CDC.
The fruit could have been contaminated at multiple points during processing -- from a sick worker in a processing plant to tainted water used for cleaning, for example. The hepatitis A virus is hardy and can survive being frozen and transported. Heat kills the virus, but frozen fruit often is either simply thawed and eaten raw, or thrown directly into a blender to make a smoothie.
"I'm sure lots of well-meaning, healthy people bought that fruit," said Dr. Philip Rosenthal, director of pediatric hepatology at UCSF. "We're not isolated. Our food comes from all over the world, including from places where there's still a lot of hepatitis A."
Hepatitis A outbreaks once were relatively common, but public health experts note that the case counts declined sharply after the vaccine was developed. One of the last major outbreaks, in 1997, was associated with frozen strawberries that were served in school lunches in Michigan; 153 people were sickened then, most of them students.
That same year, more than 30,000 cases of hepatitis A were reported nationwide, according to the CDC. In 2010, the most recent year for which data is available, there were 1,670 cases.
"When I arrived here in 1996, we were getting up to 500 cases a year. Now we see about five cases a year," said Aragon, with the San Francisco public health department. "The drop-off after vaccination started was amazing."
Aragon said about 10 people showed up at the public health department's adult vaccination clinic on Tuesday to get the hepatitis A vaccine after hearing about the current outbreak.
The CDC recommends that adults get the hepatitis A vaccine if they're going to travel to a place where the virus is active, or if they believe they've already been exposed to the virus. The vaccine can prevent illness even two weeks after exposure.
But Aragon and other public health experts said all adults should get vaccinated, regardless of whether they've been exposed to the virus or have any plans to travel.
"Is it better to get a liver transplant and be hospitalized, or get the vaccine?" said Rosenthal. "I've been vaccinated. I got that vaccine as soon as it came out."
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c.2013 San Francisco Chronicle