I Am Not Homeless

BACKGROUND: North Dakota is a low incidence state for tuberculosis (TB). Between 2007 and 2011, there were 34 cases of TB disease reported in North Dakota. The annual number of TB cases ranged from three to 12, resulting in incidence rates between 0.5 and 1.8 per 100,000. This is below the national average of 3.4 to 4.4 per 100,000 during the same time period. However, an outbreak of TB among an Urban Indian community was identified in October 2012 causing the estimated 2012 incidence rate of TB in ND to increase to 4.0/100,000.  

METHODS:  

The outbreak investigation is described below:

To be included in this outbreak cases had to be:

(1) A laboratory culture confirmed case linked to cluster G00011.

(2) A clinically diagnosed case of TB with contact to a laboratory confirmed case.

RESULTS:  

In October 2012, three cases of tuberculosis were identified in Grand Forks County. Investigations determined that these three individuals did not have permanent addresses but did not live on the streets nor reside at the local shelter. Risk factors identified for this outbreak included (1) being part of the Urban American Indian community in Grand Forks, (2) incarceration in local jails, and (3) smoking, drug and/or alcohol abuse.

Molecular Detection of Drug Resistance was the first indicator that these three cases were linked due to the presence of the silent mutation CGC>CGT; Arg528ARG.  Subsequent sensitivity patterns on the three cases revealed low level (0.2 ug/ml) isoniazid resistance which again matched the five previous cases.  Genotype results confirmed that all nine cases have the same genetic pattern matching G00011.

Twenty-one cases have been linked to this outbreak; 2 from 2010, 4 from the spring of 2012, and the remaining 15 have been identified since October 2012.  The case breakdown is as follows: 12 culture positive (57 %), 9 clinical diagnosis (43%), 11 (52%) are genotypically linked, and 6 (28%) are children under the ages of 15. There were more males (57%) than females (43%) and the ages in this outbreak ranged from 3 months to 60 years.

CONCLUSIONS:  The majority of the outbreak cases are part of a richly connected social network. Most of the cases had exposure to more than one active tuberculosis case during their infectious period as well as having multiple risk factors. Contact investigations are ongoing and the numbers of latent and active cases are likely to increase.