Raw oysters may be to blame for more than 150 people getting sick in southern California

Raw oysters may be to blame for more than 150 people getting sick in southern California, according to health officials.

More than 150 suspected local cases of gastrointestinal illness, believed to be linked to the consumption of raw oysters, were reported this week, according to the Los Angeles County Department of Public Health.

The figure is up from the 27 cases reported last week, the department added.

Officials at the Los Angeles County Department of Public Health said that the source of the illnesses, which has not yet been confirmed, is under investigation.

“Until the source is confirmed, consumers should be cautious before eating raw oysters due to the potential risk of foodborne illness,” said Dr Muntu Davis, Los Angeles County health officer, in a news release. “If you are sick, avoid spreading illness by washing your hands frequently and cleaning frequently touched surfaces such as doorknobs, light switches, and kitchen countertops.”

Public health officials warned consumers not to eat raw oysters from Laguna de Guerrero Negro and Laguna Manuela, both towns in Baja California, Mexico, as well as raw oysters from Sonora, Mexico.

It comes after San Diego County reported 41 confirmed and probable cases of norovirus illness potentially linked to raw oysters consumed in local restaurants last month. The restaurants have not been identified.

This led the US Food and Drug Administration to issue a warning to restaurants and retailers not to serve or sell oysters distributed by Sociedad Acuicola GolPac, a Seafood farm based in Sonora, Mexico, that were harvested on 18 or 27 December due to potential norovirus contamination.

Oysters contaminated with norovirus can cause illness if eaten raw, and potentially severe illness in people with compromised immune systems, according to the FDA.

Foods show no outward signs when they are contaminated with norovirus, but once a contaminated food is consumed, it can cause symptoms such as vomiting, diarrhoea, stomach pain and nausea, which develop 12 to 48 hours after being exposed. Symptoms typically dissipate within one to three days.

Norovirus can spread through direct contact, as well as through eating food or drinking liquids that are contaminated with the virus and touching surfaces or objects contaminated with norovirus, according to the federal Centers for Disease Control and Prevention.

Contracting norovirus can be prevented by washing hands thoroughly and often with soap and water.

About 48 million people a year in the US are sickened by foodborne illness, including 128,000 who are hospitalised and 3,000 who die, according to the CDC.

Last year, a man in his 30s died from a bacterial infection after eating raw oysters at a restaurant in Galveston. The man, from Texas, was believed to have had underlying health issues, authorities said.

His death came just days after the Centers for Disease Control and Prevention (CDC) issued a warning about swimming in the abnormally warm Gulf of Mexico and eating raw shellfish due to high temperatures multiplying vibrio vulnificus – a type of flesh-eating bacteria that naturally occurs in water where oysters live.

Two months earlier, a 54-year-old man died after eating raw oysters purchased from a seafood stand in Missouri.

The oysters were believed to have already been contaminated with the vibrio vulnificus bacteria when they arrived at the food stand.

In total, vibrio vulnificus bacteria causes an estimated 80,000 illnesses and 100 deaths every year, according to the CDC.