Clinical Overview of Welder's Anthrax

Key points

  • An anthrax-like illness has been documented in welders and other metalworkers.
  • Welder's anthrax is defined as pneumonia in a metalworker caused by bacteria within the B. cereus group that produces anthrax toxin.
  • Symptoms include fever or chills, cough, dyspnea, and hemoptysis.
  • Patients should receive prompt treatment with antibiotics and anthrax antitoxin.
Radiograph image of a set of lungs with welder's anthrax, which shows up as black on the xray

Overview

Welder's anthrax refers to a serious infectious disease caused by an anthrax toxin-expressing species within the Bacillus cereus group. It manifests as a severe, rapidly progressive pneumonia with systemic illness in welders and other metalworkers. It has a high fatality rate.

Causes

Several studies have shown an increased risk of pneumonia and death among welders and other workers exposed to metal fumes and mineral dusts. Research suggests it is possible that exposure to metal fumes might increase susceptibility to lung infection, even with common, relatively harmless infectious agents. Furthermore, iron oxide deposited in the lungs after inhaling welding fume has been found in the lungs for years, even after removal from exposure.

How metal fumes cause disease is mostly unknown. Theories include that metal fumes (or iron) act as a growth nutrient for bacteria, enhance the binding of bacteria to lung tissues, or impair immune responses in the lung through oxidative stress. Like all pathogens, B. anthracis and B. cereus anthrax toxins need iron to survive and thrive.

While iron overload might partially explain the increased susceptibility of welders for B. cereus infections, exposure is still important. Several researchers have noted that soil iron is much higher around welding sites than elsewhere. Future research measuring soil iron levels may provide useful information.

Known cases

CDC has identified 9 U.S. cases of welder's anthrax from 1994-2024.

  • All patients were metalworkers, and 8 were welders.
  • All patients worked in either Texas or Louisiana.
  • 6 of the 9 patients died.
  • All patients presented with severe pneumonia and were hospitalized. Among those that survived past the emergency room, all were admitted to the intensive care unit and received antibiotics.
  • 2 of 3 surviving patients received antitoxin.

Clinical features

People diagnosed with welder's anthrax had abnormal chest imaging, including pneumonia and pleural effusions. Clinicians should suspect welder's anthrax if a welder or metalworker has a severe, rapidly progressive pneumonia. Mediastinitis, which is usually seen in anthrax, is not typical in welder's anthrax.

Welder's anthrax signs and symptoms are similar to inhalation anthrax and affects the lungs. These include:

  • Fever or chills
  • Cough
  • Dyspnea
  • Hemoptysis or bloody sputum

Testing

Healthcare providers in the United States rarely see a patient with welder's anthrax. CDC guidance is available to help doctors diagnose welder's anthrax and order necessary diagnostic tests.

The only ways to confirm a diagnosis of welder's anthrax are to:

  • Test for presence of anthrax toxin genes from B. cereus group bacteria isolated from a clinical sample
  • Measure anthrax toxin in blood

Take patient samples before the patient begins taking antibiotics if it does not delay the start of treatment.

Patient management

Antibiotics

Treatment of suspected welder's anthrax initially follows guidelines for systemic anthrax with modifications based on susceptibility testing, if available. Since the B. cereus group has different innate susceptibilities than B. anthracis, modifications can be made based on susceptibility testing, if available.

Given the severity of these infections, treatment will generally be started empirically prior to confirmation. Patients should receive:

  • Two bactericidal agents from different antimicrobial drug classes
  • PLUS one protein synthesis inhibitor OR an RNA synthesis inhibitor (RNAI)

Anthrax antitoxin

After anthrax toxins have been released in the body, one possible treatment is anthrax antitoxin. Doctors must use antitoxin together with other treatment options, including antibiotics.

Anthrax antitoxin is only available through the Strategic National Stockpile.

Spotlight

CDC's Bacterial Special Pathogens Branch (BSPB) is available 24/7 for consultations on anthrax antitoxin with public health officials or healthcare providers who have urgent inquiries related to patient management. Call the CDC Emergency Operations Center at 770-488-7100 and request BSPB's on-call epidemiologist. Public health officials or healthcare providers with non-urgent inquiries should email bspb@cdc.gov and will receive a response during business hours Monday-Friday.

Reporting

Welder's anthrax is a reportable disease in all U.S. states and territories. Welder's anthrax cases must be reported to state and territorial jurisdictions when identified by a healthcare provider, hospital, or laboratory. Specific requirements for who must report cases and when to report vary by jurisdiction.

Resources

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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)
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