Outbreaks and Disease Clusters Related to Environmental Exposures

CDC’s Health Studies Program (HSP) 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, or 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, and biological agents.

When outbreaks and disease clusters related to environmental exposures occur, epidemiologists and medical toxicologists from the HSP work closely with partners to

  • determine the extent of the outbreak or cluster,
  • describe the illness,
  • identify the etiology (cause), and
  • identify the source of exposure.

The HSP’s 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

HSP investigators 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

The HSP can help investigate domestic and international outbreaks related to environmental exposures. The HSP can help in different ways, including providing technical assistance or conducting an Epi-Aid. To reach HSP outbreak response experts, contact ncehoutbreak@cdc.gov.

Outbreak and Disease Cluster Investigation Highlights

Unusual Patterns of Cancer and Environmental Concerns

The HSP provides technical assistance and helps develop guidance for state, tribal, local, and territorial health departments. The guidance focuses 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. Etiology refers to causes and risk factors associated with the development of disease. Cancer cases that are “the same or etiologically related” means that the cancer cases are of the same type, are within a family of tumors (e.g., Ewing’s family of tumors), or have a known or suggested link to the same specific environmental or chemical exposures. Health departments may request technical assistance in response to unusual patterns of cancer and cancer clusters from HSP. For more information about unusual patterns of cancer, visit the Unusual Patterns of Cancer, the Environment, and Community Concerns website.

Vast Homes and Thousands of Houses Modern Suburb Development curves layout

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. The HSP provided epidemiologic and toxicological expertise to support the field team. 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. Learn more in this MMWR article: Acute Kidney Injury Among Children Likely Associated with Diethylene Glycol–Contaminated Medications — The Gambia, June–September 2022.

Acute Non-Viral Hepatitis Associated with a Brand of Alkaline Water

Pouring glass of water from plastic bottle on blue background

In 2021, the HSP, 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 non-viral hepatitis with an unknown cause in Nevada and surrounding states. Acute non-viral 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 non-viral 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. Learn more about the investigation: Acute Nonviral Hepatitis Associated with a Brand of Alkaline Water.

Synthetic Cannabinoids

The HSP has worked with CDC’s National Center for Injury Prevention and Control to respond 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. Learn more about CDC’s work on synthetic cannabinoids: Synthetic Cannabinoids: What CDC is Doing.

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 the HSP 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. Learn more about the investigation: Liver Failure Linked to Dietary Supplements.

bottles of supplements

Unidentified Liver Disease in Ethiopia

Landscape in Gheralta in Tigray, Northern Ethiopia.

In 2007, the Ethiopia Ministry of Health and Ethiopia Health and Nutrition Research Institute asked the HSP 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. Learn more about the investigation: Unidentified Liver Disease Ethiopia.


Aflatoxin is a fungal toxin that commonly contaminates maize and other crops during production, harvest, storage, or processing. Exposure to aflatoxin is known to cause both chronic and acute liver injury. In May 2006, an outbreak of acute aflatoxicosis was reported in a region of Kenya where aflatoxin contamination of homegrown maize was a recurring problem. CDC teams worked with the Kenyan Ministry of Health to test a rapid, portable aflatoxin screening tool that could be used in the field during an outbreak. The tool helps identify contaminated maize and helps with urgent maize replacement efforts. Learn more about the investigation: Aflatoxin.

Harvested corn maize cob and grains