Hundreds of people who received communion on Christmas Day at our Lady of Lourdes Roman Catholic Church in Massapequa Park, new York, might have been exposed to hepatitis A, according to health officials, reported MSNBC.

The Nassau County Health Department is offering vaccinations this week to parishioners who received communion at our Lady of Lourdes on December 25th, said MSNBC. According to a church spokesman speaking to Newsday, the investigation is ongoing and the church is unable to identify the origin of the virus; some 7,500 parishioners attend mass at our Lady of Lourdes.

Mary Ellen Laurain, a spokeswoman for the Nassau County Department of Health, told NBC new York that, “a person involved in the communion process has tested positive for hepatitis a. The risk is low but we want to make sure that anybody who received communion on that day and those times could have been exposed.”

The Mayo Clinic writes that hepatitis a is typically contracted from contaminated food or water or from close contact with an infected individual. Mild hepatitis a cases resolve without treatment and most of those infected recover fully with no permanent liver damage. Washing hands often is among one of the best ways in which to protect oneself from the virus; vaccines are available.

Symptoms typically appear after one month following contamination and include fatigue; nausea and vomiting; abdominal pain or discomfort, especially near the liver; appetite loss; low-grade fever; dark urine; muscle pain; itching; and jaundice (yellowing of the skin and eyes), said the Mayo Clinic. these symptoms can last anywhere from two to six months, although some never develop symptoms.

Once exposed to hepatitis a, prevention can be achieved via a hepatitis a vaccine or immunoglobulin therapy within the first two weeks, said the Mayo Clinic.

The Mayo Clinic notes that hepatitis a is caused by infection with the hepatitis a virus. The virus typically spreads when a person ingests tiny amounts of contaminated fecal matter. The hepatitis a virus infects the liver cells and causes inflammation, which can impair liver function. Hepatitis a can be transmitted when an infected person handles food without first carefully washing his or her hands after using the toilet.

According to the U.S. Centers for Disease Control and Infection (CDC), wrote ABC News, ingesting food handled by an infected person is one of the more typical ways in which to contract hepatitis a.

A small number of people with hepatitis a will continue to experience signs and symptoms of infection for several weeks longer than usual, explains the Mayo Clinic. these people can exhibit symptoms, which disappear and then return over several weeks. In rare cases, hepatitis a can cause acute liver failure, a sudden loss of liver function, which requires hospitalization and, in some cases, a liver transplant, said the Mayo Clinic. The disease is most contagious about 10 days before the symptoms appear, said ABC News.

ABC News wrote that the Nassau County Department of Health is concerned that hundreds could be potentially infected. Those who attended the 10:30 a.m. and noon masses on Christmas Day are the likeliest to be at risk, the Department added.

The Nassau County Department of Health is asking that those who attended the 10:30 and noon masses at our Lady of Lourdes in Massapequa Park, new York call 1.516.227.9496, said ABC News.