Background
Since 1996, Minnesota Department of Health (MDH) has supplemented routine infectious disease surveillance with unexplained infectious deaths surveillance, usually in persons under 65 years, through the Unexplained Deaths and Critical Illness (UNEX) program. Autopsy swabs collected from decedents whose deaths appear potentially infectious or unexplained; occur outside hospitals or skilled-nursing facilities or are not considered natural; and where an autopsy or external exam was performed are submitted by medical examiners (MEs) and coroners to UNEX for standardized infectious disease testing. After the first identified positive SARS-CoV-2 test in Minnesota, MDH partnered with mortuaries to expand UNEX surveillance. To better understand potentially infectious disease-associated deaths, we describe findings from expanded (mortuary) and standard (ME) UNEX surveillance during the COVID-19 pandemic.

Methods
We collected postmortem swabs from decedents with an infectious prodrome or exposure before death, but no known recent infectious disease testing. Postmortem nasal pharyngeal and lung swabs were tested by nucleic acid amplification and viral culture using a standard testing algorithm for SARS-CoV-2, influenza, and other reportable and non-reportable pathogens. Data collected during March 2, 2020–December 31, 2021 were reviewed and characterized by source (mortuary or ME).

Results
UNEX identified 182 mortuary and 975 ME decedents. Mortuary decedents were older than ME decedents (median: 78 vs 46 years). Among mortuary decedents, 72 (40%) had SARS-CoV-2 detections. Other reportable pathogens included Legionella pneumophila (1) and influenza A (1). Among ME decedents, 189 (20%) had SARS-CoV-2 detections. One mortuary decedent had a SARS-CoV-2 co-detection (Rhinovirus). Fifty-six ME decedents had co-detections: 26 (3%) Haemophilus influenzae, 24 (2%) Streptococcus pneumoniae, 7 (1%) Bocavirus, 5 (1%) metapneumovirus, 10 (1%) Rhinovirus/enterovirus, and 1 (<1%) adenovirus.

Conclusion
Expanded and standard UNEX surveillance identified COVID-19 and other infectious disease deaths, reducing underreporting. Prioritizing postmortem infectious disease testing has demonstrated public health value.