As San Diego’s hepatitis A outbreak has continued to grow, so too has a fascination about the identity and importance of “patient zero,” the first person believed to be infected in a surge of illness that has now killed 19 people.
At first unwilling to say much at all about this mysterious person, county health officials disclosed twice during public meetings in late September that the apparent first patient — what epidemiologists often call an outbreak’s “index case”— was a homeless man who tested positive for hepatitis infection in East County.
Dr. Eric McDonald, chief of the county’s Epidemiology and Immunization Services Branch, reiterated in an email this week that this man was treated in a La Mesa hospital and “when interviewed said that the exposure period was mainly in El Cajon.”
Further details on exactly where in El Cajon, and where else patient zero might have lived, have not been forthcoming and a lack of genetic analysis due to his unknown whereabouts have made absolute confirmation of his first-patient status impossible.
Though most of the outreach and sanitation efforts have focused on the city of San Diego, and a recently-released list of cases by zip code shows that the largest number of cases occurred downtown, some have taken note that the current public health crisis may have started somewhere else.
“Patient zero coming from a different part of the county speaks to how we need to have every part of the community stepping up to solve this problem,” said James Haug, a downtown condo owner and president of the East Village Association, a business improvement district.
There’s been at least a small impact on downtown business: A cookie convention slated to hold its event at the San Diego Convention Center in September chose to withdraw until the outbreak is deemed over, though local officials challenged whether hepatitis was the true rationale.
Michael Trimble, executive director of the Gaslamp Quarter business association, said there’s no hard evidence that there’s been an impact on business.
“It’s definitely on everyone’s mind,” he said. “I’m sure there are some people who just won’t come downtown because of hep A, but I’m looking out my window right now and seeing two families with their kids strolling down Fifth Avenue.”
While he said it’s “good to know” that the first patient may have been in East County, downtown still has a large population of homeless people and it’s important to continue getting that at-risk population immunized against the virus.
Thousands of San Diegans have lined up to get the vaccine to protect against the disease, which has been tied to fecal matter contamination. Sidewalks are now being washed with a bleach solution and outreach teams have fanned out across the region.
Health officials and those in county government have resisted pinning the origin on any specific area. On Tuesday, Dr. Wilma Wooten, the county’s public health officer, again said that zip codes simply don’t mean too much when the population that’s getting sick is homeless and highly migratory.
“The zip code that they might give when someone interviews them at the hospital might not necessarily be where they hang their hat all of the time,” Wooten said.
And there is another caveat in this origin story.
Standard epidemiological practice considers a person part of an outbreak if there are enough facts to make a logical connection.
In the case of the locals outbreak, the El Cajon patient is considered patient zero because he was homeless and a blood test showed the presence of hepatitis A antibodies, according to county epidemiologist McDonald. Those two facts are enough to make it statistically likely he was infected by one of the 15 or more hepatitis A viral strains that have caused the outbreak.
But no local public health investigator has ever interviewed or traced this first patient’s movements through the community, because they have been unable to find him.
That’s too bad, because outbreak investigations work through a process called “contact tracing” which seek out each person who was in contact with an infectious person. Making contact with first patients early on allows a public health department to more accurately focus their vaccination efforts.
While a name was recorded when the individual was seen in the hospital in late November, Wooten said he was treated and released long before anyone at the county realized that an outbreak was underway in March of this year.
“We have not had the ability to contact the first index case in this outbreak,” Wooten said.
To date, because the man has not been located, his blood has not been able to be analyzed for the same strain of hepatitis that is causing the outbreak.
So, it’s technically possible that “patient zero” was actually infected by a hepatitis A virus with a different genetic fingerprint not directly related to the outbreak cases.
This disease, after all, has always been present at low levels in the community. According to local public health records, the region averaged 28 acute hepatitis cases per year from 2012 through 2016.