By NewsDesk  @infectiousdiseasenews

In a follow-up on the gastrointestinal outbreak among passengers and crew on the Princess Cruises Caribbean Princess, that returned 3 days early from its two week voyage last week, the Centers for Disease Control and Prevention reports 30-plus illnesses.

Image/CDC

According to the CDC today, 371 of 3,035 passengers and 32 of 1,161 crew have been sickened, 12,2 percent and 2.8 percent, respectively.

Officials say the causative agent remains unknown to date.

Norovirus is a highly contagious viral illness that often goes by other names, such as viral gastroenteritis, stomach flu, and food poisoning.

The symptoms include nausea, vomiting, diarrhea, and some stomach cramping. Sometimes people additionally have a low-grade fever, chills,headache, muscle aches, and a general sense of tiredness. The illness often begins suddenly, and the infected person may feel very sick. In most people, the illness is self-limiting with symptoms lasting for about 1 or 2 days. In general, children experience more vomiting than adults do.

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Norovirus is spread person to person particularly in crowded, closed places. Norovirus is typically spread through contaminated food and water, touching surfaces or objects contaminated with norovirus and then putting your hand or fingers in your mouth and close contact with someone who is vomiting or has diarrhea.

Norovirus causes more than 20 million illnesses annually in the US, and it is the leading cause of gastroenteritis outbreaks in the United States.