Outbreaks and Disease Clusters Related to Environmental Exposures

Overview

CDC provides subject matter expertise in epidemiology and medical toxicology to investigate outbreaks and disease clusters related to environmental exposures. These non-infectious disease outbreaks and disease clusters can be caused by exposures to:

• Toxins
• Chemicals
• Other substances found in the environment

Epidemiology is the study of the distribution and causes of diseases and other health outcomes in populations. Medical toxicology is the field of medicine that focuses on the diagnosis, management, and prevention of poisoning and other adverse health effects caused by:

• Medications
• Occupational and environmental toxins
• Radiation
• Biological agents

How outbreaks are investigated

When outbreaks and disease clusters related to environmental exposures occur, epidemiologists and medical toxicologists from CDC work with partners to:

• Determine the extent of the outbreak or cluster
• Describe the illness
• Identify the etiology (cause)
• Identify the source of exposure

Partners include federal, state, local, and international public health agencies.

To help answer questions, they collect different types of data, including:

• Epidemiologic data, such as who got sick, when, and where
• Clinical data, such as patient signs and symptoms
• Laboratory data, such as test results from biological specimens or environmental samples

CDC investigators also use poison center data to identify outbreaks and disease clusters related to emerging environmental hazards. For more information, see the National Chemical and Radiological Surveillance Program webpage.

Epidemiologic assistance

CDC can help investigate domestic and international outbreaks related to environmental exposures. CDC can help in different ways, including providing technical assistance or conducting an Epi-Aid.

To contact CDC outbreak response experts, email ncehoutbreak@cdc.gov.

Outbreak and disease cluster investigation highlights

Unusual patterns of cancer and environmental concerns

CDC provides technical assistance and helps develop guidance for state, tribal, local, and territorial health departments on responding to concerns about unusual patterns of cancer and cancer clusters. A cancer cluster is defined as a greater than expected number of the same or etiologically-related cancer cases that occurs within a group of people in a geographic area over a specified period.

Health departments may request technical assistance in response to unusual patterns of cancer and cancer clusters from CDC.

Severe illness associated with consuming mushroom-containing chocolate products

In the spring of 2024, America's Poison Centers and the Arizona Department of Health Services alerted CDC to several cases of severe illness in people who had consumed Diamond Shruumz^TM brand chocolate bars. These "microdosing" products were marketed as containing psychoactive mushroom extracts.

Reported symptoms included seizures, decreased levels of consciousness, respiratory failure, hallucinations, abnormal heart rates, high or low blood pressure, and gastrointestinal effects (e.g., nausea, vomiting, or abdominal pain). CDC and the U.S. Food and Drug Administration (FDA) promptly coordinated a nationwide outbreak investigation. The investigation led to a nationwide product recall and a public health response, resulting in the identification of 180 cases across 34 states.

Outbreak linked to morel mushroom exposure

During March–April 2023, 51 people reported gastrointestinal illness after eating at a sushi restaurant in Montana. The outbreak resulted in multiple severe outcomes, including three hospitalizations and two deaths. CDC worked with the Montana Department of Public Health and Human Services and the Gallatin City-County Health Department to investigate. The investigation found that eating raw or partially cooked morel mushrooms at the restaurant was strongly associated with developing gastrointestinal illness. Additionally, people who reported eating a greater quantity of sushi containing morels were more likely to develop illness compared to those who reported eating fewer pieces.

Acute kidney injury among children likely associated with diethylene glycol–contaminated medications

In 2022, The Gambia’s Ministry of Health requested assistance from CDC to help investigate a large cluster of acute kidney injury (AKI) among young children. The investigation involved multiple international partners and personnel from across CDC. Together, they were able to characterize the illness, describe the epidemiology, and identify potential causes and their sources.

The investigation found that in 2022, 78 children were suspected to have AKI, and 66 died. Most patients (75%) were younger than two years of age. After conducting interviews and analyzing medication samples, investigators found that the cause of the illness was likely medications contaminated with diethylene glycol.

Acute nonviral hepatitis associated with a brand of alkaline water

In 2021, CDC, the U.S. Food and Drug Administration (FDA), the Nevada Department of Health and Human Services, and the Southern Nevada Health District investigated cases of acute nonviral hepatitis with an unknown cause in Nevada and surrounding states. Acute nonviral hepatitis is liver inflammation that occurs suddenly and can lead to liver failure. The investigation found 21 probable cases and four suspected cases of acute nonviral hepatitis linked to consuming "Real Water," a brand of alkaline water. Eighteen probable cases and four suspected cases were identified in Nevada, and three probable cases were identified in California.

Synthetic cannabinoids

CDC has responded to numerous outbreaks of illnesses related to synthetic cannabinoids. Synthetic cannabinoid products usually consist of various man-made chemicals. Reported side effects from these products are often severe and can include kidney failure, heart attack, and death.

Liver failure associated with dietary supplements

On September 9, 2013, the Hawaii Department of Health (HDOH) was notified by a hospital that it had observed seven patients with acute hepatitis and liver failure of unknown cause. All patients reported using a dietary supplement marketed for weight loss and muscle gain. As a result, HDOH requested assistance from CDC and the FDA to identify other illnesses, describe common clinical features, and characterize risk factors for illness. In all, investigators identified 92 cases of acute hepatitis of unknown cause.

Unidentified liver disease in Ethiopia

In 2007, the Ethiopia Ministry of Health and Ethiopia Health and Nutrition Research Institute asked CDC and other partners to help investigate an outbreak of an unidentified liver disease. After conducting an extensive investigation, the cause of the outbreak was found to be exposure to toxic pyrrolizidine alkaloids.