Re: why is it safe to sit on park benches? Or is it?

Hi Jeff,

These are really good questions – I’ll do my best to answer them.

We are constantly in contact with microbes: bacteria, fungi, viruses, all known as “germs.” Not all of these cause problems, in fact, many microbes are beneficial to us. We have trillions of microbes associated with us that are essential for normal health. These microbes live on our skin, in our mouth, nose, ears, and gut - and actually play an important role in preventing infection by dangerous microbes by out-competing them for space and resources.

There are subsets of microbes, called pathogens, which cause disease. You named one: rabies – a virus that is transmitted from infected animals, like dogs, to humans, through a bite (the virus is found in the animal’s saliva). It is theoretically possible to contract rabies if an infected animal urinated onto a park bench, and then the urine touched a person’s open wound before it dried out or was exposed to sunlight. However, this is extremely unlikely to happen.

Rabies is quite rare in the US, since infected animals are killed, and healthy animals and humans are often vaccinated.

Rabies is a very fragile virus - it can be inactivated by drying, heating, or exposure to sunlight, ultraviolet light, ethanol (alcohol), and 20% soap solutions [StatRef, Ed. Jay H. Stein, M.D. et. al. Mosby, Inc 1998].

So the sunlight and dryness on a park bench, hammock, or chair would inactivate this virus before it had a chance to infect you. This is the case for many other microbes.

However, there are germs that are very hardy and would survive on a park bench, even if it is dry and sunny. For example, spores can survive in very harsh conditions for long periods of time. Some bacteria and fungi can be found in spore form, and might be on a park bench. Mold spores are found in many locations, including kitchens – this is how molds start growing on bread you leave out for too long. Most of these are completely harmless to a healthy person with an intact immune system.

Even though there are germs all around us, healthy people don’t often get sick because their immune systems fight off any threatening germs. Those whose immune systems are compromised due to illness (chemotherapy patients, AIDS patients, elderly people) need to be more careful and would be advised to minimize their exposure to germs.

So to summarize: germs are mostly harmless to healthy people and you are very unlikely to get sick from sitting on a park bench.

The full reference:
INTERNAL MEDICINE, STEIN - 5th Ed. (1998)
PART EIGHT INFECTIOUS DISEASES
IV ORGANISMS INFECTIVE TO HUMANS
CHAPTER 252 Rabies
VIROLOGY
Editor: Jay H. Stein, M.D. et. al.