Invasive Group A Strep Among People Who Inject Drugs or Are Homeless, New Mexico, 2018

In spring 2018 the New Mexico Department of Health asked CDC for help with a rise in invasive group A Streptococcus (GAS) infections picked up by the state's Active Bacterial Core surveillance. From 2013 to 2017 the annual rate climbed about 120%, from 6.8 to 14.9 per 100,000 people — roughly double the estimated national rate.

Over the same years, among 1,108 patients with invasive GAS:

• the share whose medical records noted injection drug use rose about 200%, from 6.4% (9 of 141) to 20.1% (62 of 308);
• the share noted as homeless rose 125%, from 3.6% (5 of 141) to 8.1% (25 of 308).

Injection drug use is a known risk factor for GAS, but the behaviors driving this increase were unknown. Outbreaks among people experiencing homelessness had been reported in Canada, Europe, Arizona and Alaska, yet homelessness was not a well-defined risk factor in the United States.

The investigation

From May 1 to 23, 2018, the state and CDC used daily laboratory lists to find adults aged 18–65 hospitalized with GAS (excluding throat and urine cultures) at four hospital systems in Albuquerque and Santa Fe. Patients were interviewed with a standard questionnaire on known risk factors — contact with sick children, crowding, drug injection, diabetes, chronic liver disease, skin breakdown — and possible ones such as poor hygiene, injection practices and sharing drug equipment, and their charts were reviewed. The team also interviewed staff of organizations serving people who inject drugs and people experiencing homelessness.

What they found

Of 35 patients identified, 26 (74%) could be reached. Their mean age was 48 (range 24–63); 17 were male, 7 American Indian and 15 Hispanic or Latino. About half had cellulitis and about a third abscesses.

• Skin breakdown was the most common known risk factor: recent in 21 patients (80.8%) and current in 20 (76.9%). Fifteen had seen a wound-care provider in the month before admission.
• Homelessness: 8 patients were experiencing homelessness. None reported staying in crowded places such as shelters, but six reported recent and five current skin breakdown, and six had seen a wound-care provider before admission.
• Injection drug use: 3 patients injected drugs — heroin, cocaine and methamphetamine, alone or together. All three injected several times a day, two reused the same needle, and one shared needles and licked the needle before injecting.

The 15 providers interviewed described barriers to hygiene and skin care in both groups: little access to clean running water, showers or bathrooms; poverty; and alcohol and drug addiction. Seven suggested educational tools for these groups and the people who work with them.

What it suggests

More invasive GAS among people who are homeless or inject drugs may have contributed to New Mexico's overall rise, but this pilot was too small to pin down specific risk behaviors; repeating it elsewhere could help. Because most patients had already been seen by the health care system, providers caring for these groups should be alert to the risk of severe GAS infection. Educational materials on GAS symptoms, hygiene and skin care, and safe injection practices could help both patients and providers.

Sources

• Valenciano SJ, McMullen C, Torres S, Smelser C, Matanock A, Van Beneden C. "Notes from the Field: Identifying Risk Behaviors for Invasive Group A Streptococcus Infections Among Persons Who Inject Drugs and Persons Experiencing Homelessness — New Mexico, May 2018." MMWR 68(8). CDC.