What Is Norovirus? Should We Be Worried About It?

It has been a week since the alarming reports came out about the gastroenteritis outbreak in Baguio City. The city's health services department documented over 3,000 self-reported cases of acute gastroenteritis, with 691 individuals seeking hospital consultations.

In more recent news, acting city health officer Dr. Celia Brillantes said out of the 10 stool samples from the Baguio General Hospital that were submitted to the Research Institute for Tropical Medicine (RITM), five were found to be positive for Novovirus, three were positive for Sapovirus, and two were positive for both Norovirus and Sapovirus.

While findings on the main cause of contamination remain inconclusive, Dr. Donnabel Panes of the City Epidemiology and Surveillance Unit (CESU) said Norovirus and Sapovirus, are considered the "most common causes of acute viral outbreak now."

Health Undersecretary Eric Tayag has indicated that the outbreak is currently under control, with the case count having dropped to "less than 20" recently. However, it remains essential to understand the underlying causes.

What is Norovirus?

Norovirus, previously called Norwalk virus, is a highly contagious human enteric pathogen (bacteria that affects the human digestive system) that causes vomiting and diarrhea.

According to the Centers for Disease Control and Prevention (CDC), individuals across all age groups are susceptible to norovirus. A norovirus infection can recur throughout one's lifetime due to the existence of numerous norovirus strains.

The primary symptoms of this type of infection include diarrhea, vomiting, nausea, and stomach pain. Individuals who are infected may also suffer from fever, headache, and body aches. The virus also results in the swelling of the stomach and intestines, a condition called acute gastroenteritis.

Symptoms typically emerge 12 to 48 hours following exposure to norovirus in an individual. The majority of people afflicted with norovirus start feeling better between one to three days, but they may continue to be contagious for several days following recovery. Patients suffering from norovirus may experience severe sickness and vomiting or diarrhea throughout the day, which could lead to dehydration, particularly in young children, older adults, and people with other illnesses.

How it spreads

Norovirus is highly infectious and can rapidly spread through various transmission methods. It can be contracted by accidentally ingesting microscopic particles of feces or vomit from an individual who has the virus. If one becomes ill with norovirus, that person may release billions of microscopic norovirus particles.

Norovirus transmission can occur by directly interacting with an infected individual, such as when providing care, sharing food or cutlery, or consuming food that this person has touched. Norovirus can also be contracted through the ingestion of food or drinks that have been contaminated with the virus, as well as by touching surfaces that are contaminated.

In a recent press briefing, Dr. Panes mentioned that transmission can occur through contaminated food and water. Thus, people in Baguio City are currently advised to use treated water (either purified or distilled water) for both drinking and cooking. "We also have to continue practicing good hand hygiene, such as washing our hands before and after using the toilet, before and after eating, and when caring for sick household members," advised Dr. Ian Christian Gonzales of the Department of Health's Epidemiological Bureau.

Sapovirus, which also belongs to the Caliciviridae family, also causes gastroenteritis and is transmitted in much the same way.

According to Dr. Panes, there have been acute gastroenteritis outbreaks in the Philippines in the past. Unfortunately, it was only in 2021 when the country started to have the capacity to identify and document Norovirus and Sapovirus. 

Currently, there is no approved vaccine yet to prevent infection by norovirus.