A new study finds that Zika virus, which is already linked to paralysis and birth defects, also may be associated with a deadly type of brain inflammation.

Researchers found the Zika virus in the spinal fluid of an 81-year-old man with meningoencephalitis, a dangerous inflammation of the membranes that surround the brain, according to a report from French researchers in The New England Journal of Medicine.

The man had been on a cruise in the South Pacific near New Zealand, New Caledonia, Vanuatu and the Solomon Islands.

Although Zika is now spreading in the Americas, it caused an outbreak in French Polynesia from 2013 to 2014 and is spreading on several island groups in the Pacific, including New Caledonia and American Samoa, according to the Centers for Disease Control and Prevention.

The man had been in "perfect health" before becoming ill, according to the report. After returning from the cruise, however, he developed a fever and slipped into a coma. Doctors inserted a tube into his trachea in order to help him breathe and put him on a ventilator. The man developed a rash within 48 hours. He woke up from his coma 24 hours after doctors put in his breathing tube, but experienced hallucinations and weakness in his left arm. The man's condition improved, even though doctors gave him no specific treatment, and he was discharged from the intensive care unit after 17 days. His mental functioning was normal again after 38 days, although his left arm remained weak.

Zika is spread primarily by Aedes aegypti mosquitoes. Other diseases spread by this mosquito species, including dengue and West Nile virus, also are known to cause meningoencephalitis, said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston.

Meningoencephalitis is a "serious condition involving direct infection of the brain, spinal cord and its linings," said Amesh Adalja, a senior associate at the Center for Health Security at the University of Pittsburgh Medical Center. "That Zika is being linked to this condition is a very serious matter and adds to the growing evidence of the full-spectrum of disease this virus can cause."