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Health officials in South Korea reported that a second person has died after being infected with an unknown virus.

According to news reports, eight patients from different parts of the country have been hospitalized in recent months with similar cold or flu-like symptoms, including cough and difficulty breathing. Seven of the eight had recently given birth or were expecting. The first victim to die was nine months pregnant; the second was also due to deliver before her death. Doctors were able to save both babies. The expectant women died of multiple organ failure triggered by severe scarring and thickening of the lung tissue.

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The Korea Centers for Disease Control and Prevention said all patients have been transferred to a hospital in the country’s capital city of Seoul, and are receiving treatment in intensive care. Two were released after receiving lung transplants.

Health officials are conducting DNA tests on the virus isolated from the patients to identify the cause of the infection. Two of the patients have tested positive for the common cold virus and adenovirus, but doctors believe these agents aren’t responsible for the more severe symptoms they have seen in the affected patients. They are investigating whether a new viral or even bacterial agent might be circulating in the country.

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