Tracing a Likely Hospital-Acquired HIV Infection With Genetic Sequencing, New York, 2017

Since Standard Precautions against bloodborne infections were introduced in 1985, transmission of HIV in U.S. health care settings has been rare. In October 2017, however, New York City and New York State health officials learned of a young man diagnosed with acute HIV infection who had no recognized risk factors — he was monogamous with an HIV-negative partner and did not inject drugs — but had recently been in the hospital for a chronic condition. With CDC, they investigated whether he had been infected during his care.

A narrow window

The patient, referred to as patient A, had chronic kidney disease.

• 99 days before diagnosis: on admission to hospital 1 in July 2017, a rapid HIV test was negative.
• 25 days before: he was readmitted to hospital 1 and began hemodialysis.
• 22 days before: he had a vascular access placed by interventional radiology at hospital 2, and began hemodialysis at hospital 1 the same day.
• 12 days before: he was discharged, and 2 days later began dialysis at an outpatient center.
• Diagnosis: readmitted with five days of fever, sore throat, nausea, vomiting and diarrhea, he was diagnosed with acute HIV the next day.

His test pattern — HIV antigen and viral RNA but no antibody yet — indicated a very recent infection, likely 10 to 22 days earlier: the span from his hospital admission to the start of outpatient dialysis. He was referred for HIV care but not prescribed antiretroviral treatment, and he died of complications of kidney disease 66 days after his HIV diagnosis.

Looking for a source

Investigators identified 232 patients treated at the same time as patient A on his hospital ward, in its hemodialysis unit, in hospital 2's interventional radiology unit, or at the outpatient dialysis center. Matching them against the state HIV registry found 10 with previously diagnosed HIV. Nine had kept their virus suppressed throughout 2017. The tenth, patient B, diagnosed decades earlier, had a rising viral load from spring to fall 2017; the hospital knew of the diagnosis and gave antiretroviral drugs during the stay. Patient B died in November 2017.

The genetic match

The state compared HIV pol gene sequences routinely generated during drug-resistance testing, and CDC sequenced leftover 2017 specimens from both patients.

• All sequences from patients A and B were more than 98% identical, and their 2017 sequences more than 99% identical.
• The other patients' viruses were less than 96% identical to theirs.
• Their viruses were not closely related to any of roughly 295,000 state sequences, 400,000 CDC sequences or 800,000 in the public GenBank database.
• In a phylogenetic analysis, all five sequences from the two patients clustered tightly together with high confidence.

How could it have happened?

Patients A and B shared the same hospital 1 ward for 25 hours in October 2017, and both received dialysis in the same inpatient unit — but never on the same day, and patient A never followed patient B on the same machine. Patient B had no interventional radiology procedures, and the two had no known social contact.

Site visits to all four settings found no directly observed infection-control lapses. The only medicines both patients received were intravenous saline flushes, from sealed, prefilled syringes kept in locked rooms, and darbepoetin, an anemia drug supplied in patient-specific, prefilled, single-use syringes. Other medicines were dispensed through an automated system with biometric and password controls.

No specific route was confirmed, but the timing and the close genetic match pointed most strongly to transmission on hospital 1's ward in mid-October 2017. The dialysis and radiology units were ruled out because there was no source patient or opportunity there. The investigators could not exclude transmission from someone with undiagnosed HIV or with no sequence available for comparison.

Response

The state recommended notifying every patient who had an injection, infusion or other invasive procedure on the same ward, or inpatient dialysis at hospital 1, while both patients were there. The hospital wrote to the 36 living patients who met those criteria, explaining the possible exposure and offering free testing for HIV and for hepatitis B and C. Ongoing surveillance found no further related cases.

Lessons

The case is a reminder of the importance of strict adherence to Standard Precautions. It also shows the value of HIV sequence analysis: when acute HIV turns up in someone with recent health care exposure and no known risk factors, investigators might consider health care-associated transmission and compare virus sequences to find it.

Sources

• Bridget J. Anderson, Ernest Clement, Randall Collura, Abigail Gallucci, Emily Westheimer, Sarah Braunstein, Karen Southwick, Eleanor Adams, Emily Lutterloh, Charles Gonzalez, Robert McDonald, Hongwei Jia, William M. Switzer, Priti R. Patel, M. Patricia Joyce and Alexandra M. Oster, "Investigation of Presumptive HIV Transmission Associated with Hospitalization Using Nucleotide Sequence Analysis — New York, 2017," Morbidity and Mortality Weekly Report, CDC: https://www.cdc.gov/mmwr/volumes/69/wr/mm6910a2.htm
• The report's figures, prepared with the New York health departments, are not reproduced.