How contagious is hepatitis A? Would I have a high chance of getting it from being in an enclosed area, such as a car or an elevator, even if I didn’t touch anything the infected person touched?
A contagious disease is one that is spread directly from one person to another, by contact or by inhaling droplets that the person has coughed up. Typical very contagious diseases are measles or chickenpox, where simply being in the same room with a sick person will give you the disease. Typical diseases that are not very contagious would be syphilis, which is virtually always transmitted through sex, or HIV which requires sexual or blood contact for transmission..
I would place hepatitis A in the not very contagious group. Casual contact, touching the skin, or being in the same room with someone who has hepatitis A will not transmit the disease. Hepatitis A is an enteric virus, meaning that it enters our body through food or water and is excreted in our stool. It is the classical disease associated with poor sanitation or sloppy food-handling practices. It is probably the major reason that health codes are passed requiring the posting of signs reading “employees must wash hands before returning to work” in restaurant toilets.
Hepatitis A is now fairly uncommon in this country, but occasional mini-epidemics do occur, usually traced to a food handler who has the disease. In the underdeveloped world, almost everyone gets hepatitis A, usually in childhood when the disease is often mild and may not even be diagnosed. I have tested many people who have antibodies to hepatitis A and are most surprised when I inform them that they must have had the disease, since they have no memory of it.
The advice given to travelers to drink only bottled drinks, eat freshly cooked food and fruits that can be peeled, and to never eat salad is designed to prevent infection with hepatitis A, as well as some other germs that cause dysentery. Shots of gamma globulin, which are protective for three months, will prevent the disease. There is now an active immunization against hepatitis A that is very effective. I would recommend it for anyone who will be travelling in underdeveloped countries, particularly in rural areas.
The circumstances that you describe, being in an enclosed space with someone with hepatitis A, poses almost no risk to you. Even if you have pretty close contact with an infected person, such as bathing them, washing their clothes, eating with them, simple measures like good hand washing, not sharing towels, and careful dish washing will prevent you from catching the disease.
There is recent evidence that people who have one of the chronic forms of hepatitis, hepatitis B or C, should be immunized against hepatitis A, since that disease tends to be much more severe in someone whose liver is already damaged by chronic hepatitis.