If I breathe in one cold virus will I catch a cold? I know that one virus can make millions so I suppose it is possible.
I vaguely remember learning about something called titre in university which states that a certain quantity of virus is needed to infect a sample but I don’t understand the concept.
Any help?
It depends on the “cold” virus you’re exposed to. There are over 100 strains of Rhinovirus, that’s just one group that causes upper respiratory symptoms. Respritory Syncytial virus causes cold symptoms in adults, but can be life threatening in infants.
Also, viruses don’t really hang out alone. If you’re exposed, it’s likely you’re exposed to a few million.
The common cold is caused by over 200 agents. Rhinovirus causes about 50%, coronavirus another 20%. What you’re looking for is called the Infectious Dose, or ID50 (the number of organisms it takes to cause infection in 50% of test subjects). Usually viruses and bacteria have ID50s of 100,000+, either because they need to overwhelm your immune system, or create biofilms to stick and invade.
I teach Microbiology, and one book I use (Tortuga, Funke, and Case) says that the infectious dose for rhinovirus is only one.
I recall reading that you can only catch each strain once, in other words, once you’ve had a couple of hundred colds, you’re immune. Of course, even if true, it doesn’t make a great deal of difference, I guess - that’s enough to last a lifetime and more anyway.
It’s not true. The memory cells that live in your mucous membranes only last a few months, as opposed to the ones in your blood that last pretty much forever.