Unexplained Critical Illnesses and Deaths of Possible Infectious Etiology (UNEX) and Medical Examiner Infectious Deaths Surveillance (MED-X), 2009

Surveillance for unexplained critical illnesses and deaths of possible infectious etiology (UNEX) began in September 1995.  Primary focus is given to cases less than 50 years of age with no significant underlying conditions, however, any case should be reported regardless of the patient’s age or underlying medical conditions to determine if further testing may be indicated. In addition to provider reporting, death certificates are reviewed for any cases under 50 years of age with no significant underlying conditions for possible unexplained infectious syndromes.  

In 2006, MN began Medical Examiner Infectious Deaths Surveillance (MED-X) to evaluate all medical examiners cases for infectious related deaths.  MDH distributes specimen collection kits to the ME offices and materials to help guide the number and type of specimens collected.  All ME offices are encouraged to participate.  MDH in particular works with the Minnesota Regional Medical Examiner Office (MRMEO), the Hennepin County Medical Examiner Office, Midwest Forensic Pathology, Ramsey County Medical Examiner Office and Lakeland Pathology.  Medical examiners report explained and unexplained cases to MDH.  Unexplained deaths in previously healthy individuals less than 50 years of age are included regardless of infectious hallmarks; this primarily includes Sudden Unexplained Infant Deaths (SUIDS).  In addition, MDH reviews death investigations at MRMEO to capture a population based rate that includes cases not autopsied.  Cases found through active surveillance that have infectious pre-mortem and/or post-mortem findings indicating a possible infectious related death for which a pathogen was not identified are also considered for UNEX surveillance and are followed-up with for testing if they are less than 50 year of age and previously healthy. 

Testing of pre-mortem and post-mortem specimens is conducted at MDH PHL and the CDC Infectious Diseases Pathology Branch (IDPB).  Cases are excluded from UNEX if they are determined to be explained by providers, are not critically ill, or have no infectious disease hallmarks.  Cases are residents of MN or are investigated by a medical examiner office in MN.

Due to the increased submission of specimens during the H1N1 pandemic and the development of an integrated UNEX/MED-X system, the numbers reported for 2009 are difficult to compare with previous years. 

There were 201 cases that met criteria for UNEX surveillance (157 deaths and 44 critical illnesses) in 2009, compared to 88 cases in 2008. Of the 201, 133 were reported by providers, 11 were found on death certificate review, 51 were found through review of medical examiner records, and 6 were found through other reporting methods.  Of the 51 found through MED-X surveillance, only 5 were less than 52 years of age and 10 had autopsies.  Among the 201 cases, 90 cases presented with respiratory symptoms; 35 with neurologic symptoms; 24 with cardiac symptoms; 16 with sudden unexpected death (SUD); 14 with shock/sepsis; 13 with an illness that did not fit a defined syndrome including more than one syndrome; five with gastrointestinal (GI) illness; and four with a hepatic syndrome. The age of cases ranged from one week to 104 years.  The median age was 29 years among 133 reported cases and 69 years among 68 non-reported cases, with an over all median age of 43 years.  Fifty percent resided in the 7-county metropolitan area and fifty percent were male.

There were 116 cases that had specimens tested at the MDH PHL and/or the CDC IDPB.  Of those, 48 had one or more pathogens identified as a potential cause of the illness (Table 1).   Cases were identified as confirmed (n=41), possible (n=4), or probable (n=3)  based on the type of testing performed, the anatomic site of the specimen and the clinical syndrome.  The most frequently identified pathogens include 21 cases of 2009 H1N1 Influenza A, 7 S. pneumoniae, and 5 S. aureus (Table 1).   There were also several cases caused by pathogens not expected to occur in Minnesota.   One case was in a 21 month-old female with onset of acute rash and sepsis following a tick bite. Serologic, PCR and IHC testing revealed an infection with Rickettsia rickettsii, commonly known as the agent of Rocky Mountain Spotted Fever (RMSF).  While there have been sporadic reports of RMSF in MN in the past, this represented the first confirmed endemic case in MN.  There was also a case of vaccine-associated poliomyelitis identified in an individual with acute flaccid paralysis.  Finally, a case of Hantavirus was identified in a 52 year old female who had recently returned to MN from a rafting trip in the southwestern United States.   

The UNEX and MED-X programs played a critical role in identifying deaths due to H1N1 in 2009.  Compared with H1N1 deaths identified through other surveillance mechanisms the case patients identified through UNEX and MED-X were younger and more often previously healthy.  Without these programs 25% of MN deaths due to H1N1 would have gone undetected. 

There were 201 MED-X cases in 2009; 127 of these also met UNEX criteria.  Based on MRMEO data, the population-based rate of potential infectious disease related deaths as reported to MEs was 14.5 per 100,000. The median age of the cases was 48 years, and 51% were male. There were 82 (41%) cases found through death investigation report review, the majority of which were cases that did not have autopsies (n=69 [84%]).  MEs reported 102 (51%) cases, death certificate review identified 16 (8%) cases, and one case was found through other reporting methods. The most common syndrome was pneumonia/upper respiratory infection (n=88 [43%]). Among the 125 autopsied cases, the most common pathologic finding was myocarditis (n=19, [15%]). Of the 201 cases, 51 (25%) were confirmed to have had an infectious cause, 127 (63%) had possible infectious causes, and 23 (11%) were due to non-infectious causes.  Pathogens determined as related to the cause of death are described above for the 127 UNEX cases.  Among those explained by the provider, pathogens identified as the confirmed or possible cause of death included Streptococcus pneumoniae (n=4), Staphylococcus aureus (n=5), Escherichia coli (n=3), Enterococcus spp. (n=3), Streptococcus spp. (n=2), and one each of clostridium difficile, Hepatitis C, Klebsiella pneumoniae, and Pseudomonas aeruginosa. 

• For up to date information see>> Unexplained Deaths and Critical Illnesses
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2009