Similarities in Symptoms of  

SARS-CoV-2 Infection and

Carbon Monoxide (CO) Poisoning

COVID-19 cases, hospitalizations, and deaths are rising across the United States. Carbon monoxide (CO) poisoning incidence also rises with the onset of cooler weather and greater use of heating systems. The symptoms of COVID-19 may overlap with symptoms of CO poisoning, including headache, dizziness, weakness, nausea, vomiting, chest pain, and altered mental status with no alternative explanation. The purpose of this COCA Now is to remind emergency department, urgent care, and other clinical professionals who are assessing patients for SARS-CoV-2 infection to consider the possibility of CO poisoning. 

When assessing a patient, if it is possible to obtain a focused history, the source of CO exposure may become apparent. Physical findings coupled with confirmatory testing and a suggestive history likely indicate CO poisoning. A high level of suspicion is needed in patients who present with general or non-specific signs and symptoms, altered mental status, or both, as obtaining a detailed history may be difficult.

The key to confirming a CO poisoning diagnosis is measuring the patient’s carboxyhemoglobin (COHgb) level. An elevated COHgb level of 2% for non-smokers and >9% COHgb level for smokers strongly supports a CO poisoning diagnosis.
  1. COHgb levels can be tested either in whole blood or by using a pulse CO-oximeter. However, any suspicion of CO poisoning should be confirmed with a COHgb level by multiple wavelength spectrophotometer (CO-oximeter) from a venous or arterial blood sample. A conventional pulse oximeter that measures oxygen saturation is not accurate in the presence of COHgb. 
  2. It is essential to know how much time has elapsed since the patient has left the toxic environment because that will impact the COHgb level. If the patient has been breathing normal room air for several hours, COHgb testing may be less useful.  
  3. Consult your local poison center (1-800-222-1222) for assistance with diagnosing and managing CO poisoning.   
Patients with suspected or confirmed CO poisoning associated with their living environment should be counseled on how to prevent CO poisoning. Strategies for preventing OC poisoning include proper installation and maintenance of a CO detector, maintenance of fuel-burning appliances, safe practices related to generators, and potentially not returning to their home until it is determined safe to do so. Notification to emergency personnel of a potential CO hazard in these patients’ homes may also be warranted.

For further information, please see CDC’s Clinical Guidance for Carbon Monoxide (CO) Poisoning.

The Emergency Risk Communication Branch in the Division of Emergency Operations, Center for Preparedness and Response is responsible for the management of all COCA Products. 

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