JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
rate per 100,000 was 3.4 ± 1.1. There was a positive trend over the study period (Cochran-Armitage chi-square test for trend = 108.88 (p = 0.000) with an annual rate of increase of 3.88%, 95% CI: 1.30 – 6.52%. The rate of increase of both Campylobacter and GBS over the study period were found to be similar (two-sample t-test = -0.10 (p = 0.920).
Campylobacteriosis
Figure 8 shows the rates per 100,000 population during the study period of campylobacteriosis. The annual case count ranged from 90-257 with a mean of 154.0 ± 54.2. The mean incidence
Figure 8: Distribution of Campylobacteriosis Rates per 100,000 Population in Louisiana from 1999-2015.
DISCUSSION
Males and females seem to be at equal risk of developing the syndrome. However, there was observed to be a positive trend among females and not males. This could be due to females becomingmore likely over the years to consult a physician when experiencing GBS syndromes compared to previous years rather than a true increase in risk of developing GBS. Whites seem to have approximately double the risk of developing GBS compared to blacks while both race seem to be experiencing a positive trend since 1999. This unexplained risk difference may also be due to a difference in access to care. The percentages of concurrent diagnoses of infections and pneumonia show no changes over the study period which is expected if these conditions do cause a portion of GBS cases throughanautoimmune response.Thepercentageof concurrent diagnoses of other neurological conditions is unexpected, however. Rather than other neurological conditions increasing in incidence alongside GBS, the practice of diagnosing more than one neurological condition when presented with a GBS-like constellation of symptoms may have increased over the years. While Zika viral disease was associated with GBS, there were no locally transmitted Zika viral infections. No GBS was reported among the cases imported from areas with Zika viral infections.
Incidence
The yearly incidence in the U.S. is estimated at 1-2 cases /100,000 population (CDC 2016). Estimates for North America, England, Iceland, Norway and Finland ranged from 0.62-2.66 /100,000 (Yoshikawa 2015, Sipilä 2017). Some reported estimates of GBS incidence for all ages combined reached 3.0 /100,000 (Mc Grogan 2009). The Louisiana rate (3-5.6 /100,000) is higher than rates reported by other countries. The lack of standardization of case definitionsmay account for this discrepancy. It is reasonable to assume that Louisiana rates are not very dissimilar from that of other countries. The data from LAHIDD seems to indicate a steadily increasing burden of GBS in Louisiana with an annual rate of increase of about 3% which equates to approximately 6 additional cases each year. This positive trend seems to be driven by the increase in incidence rates of the 35-64 age group, although the 65+ age group continues to have the highest incidence rate of GBS, nearly twice that of the 55-64 age group which has the next highest incidence rate among all age groups. The largest single year decrease observed in the incidence rate per 100,000 population occurred between 2004 and 2005. This artifact can be seen across most demographic groups and is most likely explained by the impact Hurricane Katrina had on the provision of healthcare across the Gulf Coast in August of 2005.
The incidence of campylobacteriosis as measured through Louisiana’s NBS database experienced a similar trend over the
112 La State Med Soc VOL 170 JULY/AUG 2018
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