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San Diego's Hepatitis A Outbreak
By Acting More Quickly, the County and City of San Diego Might Have Reduced the Spread of the Disease

Report Number: 2018-116

Figure 1
The Number of New Hepatitis A Outbreak Cases Each Week Did Not Start Steadily Decreasing Until September 2017

This vertical bar chart depicts the number of new hepatitis A outbreak cases per week that occurred in San Diego County from November 2016 through January 2018. The chart shows that from mid-November 2016 through mid-February 2017 the county experienced a few new hepatitis A cases every two to three weeks. However, from late-February 2017 through the end of January 2018 the county experienced new hepatitis A cases each week. In March 2017, the number of new hepatitis A outbreak cases that occurred in the county began increasing significantly, and did not start decreasing steadily until mid-September 2017. The county announced a hepatitis A outbreak on March 10, 2017, and the number of new cases that week was five. By the second week of April 2017, the county experienced ten or more new cases per week, and from May through mid-September 2017, the county averaged 20 new cases per week. The county declared a local health emergency on September 1, 2017, and experienced the peak of 29 new cases that week. During the following two weeks the county experienced 19 and 13 new cases, respectively. From this point through December 2017, the number of new cases each week dropped significantly. From the first week of October 2017 through mid-November 2017, the county experienced 11 or less new cases per week. In the weeks from mid-November through the end of January 2018, the county experienced one new case during seven of the weeks, and between two and four during the other five weeks.

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Figure 2
New Monthly Hepatitis A Cases Declined When the County and Other Providers Significantly Increased the Number of Vaccinations They Administered

This combination line and stacked bar chart shows that the number of new monthly hepatitis A cases declined after the county and other providers significantly increased the number of vaccinations they administered. Other providers includes county programs, public health centers, community clinics, hospitals, health plans, pharmacies, and private providers. A line graph shows the number of new monthly cases increased from less than 10 during February 2017 to 28 during March 2017. From May 2017 through September 2017 the county experienced an average of 84 new cases per month, with a sharp increase in new cases during May followed by a slight drop during June. The number of new case increased again in July and peaked in August. During this period, the county and other providers provided less than 8,000 vaccines per month from January 2017 through August 2017. A bar graph shows the number of vaccinations administered slightly increased starting in April, with a larger increase to approximately 8,000 in August. On September 1, 2017, the county declared a local health emergency, and the county and other providers administered over 40,000 vaccines during both September and October. The line graph shows the number of new cases during October dropped to 36 from about 80 during September, and continuously decreased through January 2018. In January, the number of new cases was five, and on January 23, 2018, the county’s Board of Supervisors allowed the local health emergency to end.

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