COMMENTARY

California Contagion: How to Control Severe Hepatitis A

Paul G. Auwaerter, MD

Disclosures

December 14, 2017

Hello. This is Paul Auwaerter, speaking for Medscape Infectious Diseases, from the Johns Hopkins University School of Medicine. The recent outbreak of hepatitis A among homeless populations in San Diego (as well as Santa Cruz and Los Angeles), California, brings to mind several key issues that might be useful for infectious diseases clinicians and practitioners in general.

First, hepatitis A is often viewed as a benign disease, especially because routine immunization in children has changed the epidemiology. [Historically] seen as an asymptomatic disease in children, acquired by the fecal-oral route or by eating contaminated food or drinking contaminated water, more than 75% of current cases of hepatitis A are in adults as opposed to children.

The public health department in San Diego has reported 507 cases as of mid-October 2017, with 69% hospitalized and a mortality rate of 3.7%.[1] [Editor's Note: On December 4, 2017, there were 567 cases reported in San Diego, with 67% hospitalized and a 3.5% mortality rate.] Contrast this to the last reported national surveillance from the Centers for Disease Control and Prevention for hepatitis A in 2015,[2] where there were only 1390 cases reported in the country, a 1% mortality rate, and a 47% hospitalization rate.

What is happening in San Diego seems more severe. Why? It could be that this population is seeking care later, is being identified as ill later, is a more chronically ill population, or perhaps there are some strain virulence factors as well. If fulminant hepatitis does develop, the mortality rate is 90%. Hepatitis A is often not seen as a severe disease, but it certainly can be, and it can lead to death or to the need for liver transplantation.

On the flip side, diagnostically, the hepatitis A immunoglobulin M serology has been the go-to test.[3] It's quick, generally widely available, and will be positive, with the onset of symptoms and elevated liver function tests, 14 to 45 days after acquiring the virus, in terms of an incubation period. A 99% accuracy is often purported. However, what is happening in this epidemic population is that people who may be worried that they could be exposed to hepatitis (but who are not in an at-risk group such as the homeless) might have a more pedestrian/viral illness but are asking to be tested.

In this type of low-prevalence population, you start seeing more false-positive results, which has also been reported in the literature as well.[4,5] Public health officials are having difficulty sorting out true positives in this population, although many of these people, of course, don't develop hepatitis.[4,5] A positive assay requires investigation and resources. A hepatitis A RNA test (polymerase chain reaction) can help, although this test is not widely available. Another key point is that unless there are risk factors, reflex testing for hepatitis A serology probably should not be done. The test requires some pretest probability before ordering, or it can create more confusion.

The last issue is that when we are dealing with a public health crisis, it is interesting that the vaccine supply in the country has been somewhat exhausted. The state of California has requested emergency vaccine resources,[6] and Merck has had some difficulties in the manufacturing process. The requirements to stem this epidemic and immunize people are hindered by lack of [vaccine] availability. I think this reflects our just-in-time [approach] to minimize manufacturing and stocking costs.

I am not sure that there are any easy solutions from a public health perspective, but this is just one of the challenges as we face an epidemic. Hepatitis A has not been on the radar in many years, after the introduction of routine immunization. Obviously, there are still at-risk populations.

Thank you for listening. I certainly hope the hepatitis A cases do decline, although there have been predictions that this can go on for months or even longer, given how this virus can be spread.

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