Question: how can diseases transfer from person to person?

Clare Taylor answered on 21 Nov 2012:

Excellent question Henry and right up my street!

Infectious diseases can be passed from person-person in several different ways:

Direct contact, e.g. direct contact with infected body fluid, common for sexually transmitted infections like HIV, chlamydia, human papilloma virus, or from exchange of saliva, like in the case of glandular fever, also known as kissing disease – you can guess how you get that, right?

Or from ingestion (usually unknowingly) of bacteria via the ‘faecal-oral’ route. Yes, that sounds horrible and that it is what it sounds like! This is common for spread of diseases like typhoid fever and cholera and where you may unknowingly pick up infectious bacteria after someone infected else has touched something, but they haven’t washed their hands properly after going to the toilet. Sounds yuck but it’s true! This also happens when infectious bacteria found in faeces get into the water supply and you drink it.

Inhalation is another way e.g. in the case of TB, where people inhale air droplets that are filled with infectious bacteria that have been coughed up by an infected person. This is also how norovirus spreads, also known as the winter vomiting virus. The virus makes people projectile vomit (nice…) millions of virus particles into the air. If you then breathe some of these in, you’ll probably get the same disease… If this happens in a hospital, it can close whole wards down.

Here’s a frightening thing. Have you heard of Ebola virus? It’s a really nasty virus that basically causes people to bleed to death inside and is 90% fatal. We thought that this was only spread from direct contact, i.e. physical contact, but scientists now think that it may be able to spread through the air. How scary is that? We need scientists to do some research on this quickly, but as you can imagine it’s dangerous for the scientists…

It sounds to me Henry, that you might be a budding microbiologist… I highly recommend it!