The West Nile virus is spreading at an alarming rate in Greece, raising the alarm among health authorities.

The number of confirmed cases has increased significantly over the past week, while the number of victims has risen to six, all people over the age of 65. Of those infected, 54 have developed complications in the central nervous system, such as encephalitis, meningitis or acute paralysis. Twenty patients continue to be treated in hospitals, eight of them in intensive care.

The main outbreaks are in Attica, which includes the Athens area, as well as in Thessaly and Central Macedonia. Health authorities speak of a particularly high circulation of the virus in Attica, while several other areas have been declared high-risk, although they have not yet recorded any human cases.

West Nile virus is transmitted primarily through the bite of infected mosquitoes. Mosquitoes catch the virus from birds, and it is not spread from person to person through casual contact.

About 80 percent of those infected show no symptoms. Most others experience a mild, flu-like illness, while less than one percent develop serious neurological complications.

The elderly, people with chronic illnesses and those with weakened immune systems are most at risk. Authorities warn that the virus transmission season continues and that new cases may appear in other regions.