Investigating Unexplained Illness & Death

The investigation of unexplained illnesses and deaths is a major component of IDPB pathology work.

As a result of this work over the past 30 years, many new disease-causing agents have been identified in the US. The following illnesses were identified through a study of outbreaks of unknown severe illness and death:

• Legionnaire’s disease (LD)
• Toxic shock syndrome (TSS)
• Acquired immune deficiency syndrome (AIDS)
• Hantavirus pulmonary syndrome (HPS)
  also see IDPB’s contributions: Surveillance of hantavirus pulmonary syndrome
• West Nile virus (WNV) encephalitis

Each of the newly-identified agents caused illness before the outbreaks, according to later studies. These studies were successful because of the use of pathology. Scientists examined tissue specimens saved from patients with unknown illness. The stored tissues showed that these agents had been causing illness for several years before they were identified.

For example, in 1976, there was an outbreak of Legionnaire’s disease. The bacterium Legionella pneumophila was found to be the cause of the illness. No one had identified this bacterium before 1976. Scientists then began to look at older cases that were like those of the outbreak. They found that people had this illness prior to 1976. In fact, this disease had caused another outbreak in 1957 and other cases as far back as 1947.

Likewise, toxic shock syndrome was first recognized in 1979. Cases were later identified from as early as 1960. AIDS was initially described in 1981, but studies have revealed a case from 1968. Even more surprising was a case of hantavirus pulmonary syndrome (HPS). This disease was discovered as part of a 1993 outbreak in the Southwest U.S. When old cases of unexplained illness in that region were reviewed, a case from 1959 was discovered.

Recent advances in technology can boost our ability to spot new infections earlier than in the past. Experts in IDPB have had great success in diagnosing infections. IDPB is often called upon to take the lead when deaths occur due to unknown infectious agents.

Each year, cases from all over the world are sent to IDPB. For many cases, the cause of illness is unknown. IDPB staff with knowledge in a variety of fields discuss each case. Depending on the case, a range of tests may be performed. The branch evaluates hundreds of cases each year. For many cases, testing by IDPB results in pathogen identification. Identified diseases have included those of public health importance, such as reportable conditions, vaccine-preventable diseases, and emerging infectious diseases.

If you are a physician or are associated with a government health agency, please see Specimen Submission Guidelines for information on how to submit cases to IDPB for testing.