Did I catch a cold from eating unwashed fruit?

Question

Recently I caught a cold in presumably an amazingly short period of time (~6h). From prior infections I had the experience to have 24 to 48 hours "left" being a bit ill, before being forced to stay in bed. Observing my disease I asked myself what went different this time. In general I don't get ill too easy.

• Morning: got to work as usual feeling reasonably well
• 12pm: ate some sushi bought from a supermarket
• ~3 pm: ate a bowl of strawberries - unwashed
• 6pm: already felt a scratchy throat
• 9pm: having a Skype call planning some event, starting to have a headache
• 11pm: falling to bed really exhausted
• I did not have contact with visibly ill people during that day.

My theory now is, that the unwashed strawberries carried the pathogen. Here are some thoughts that might support this:

1. Since I got hit so fast I'm assuming being exposed to a high number of bacteria.

2. The pathogens where possibly passed by an ill harvester.

3. Strawberries being sweet, moist and un-chilled seem to be the perfect fertile ground for reproduction.

4. The incubation period of colds is usually a lot longer (2-5 days). Does a higher number of bacteria result in a shorter incubation period?

5. Washing the strawberries would have helped. The bacteria was just on the surface area, since the vessels of the strawberries of course where not alive anymore.

Am I right with my assumptions or did I miss something? I'd like you to confirm or debunk my theory of getting ill.

Thank you!

Answer 1

Unlikely.

There are different viruses responsible for the symptoms grouped together as "common cold":

.....................................   
:     Virus     : Incubation period :   
:...............:...................:   
: Adenovirus    : 4-8 days          :   
: Coronaviruses : 2-5 days          :    
: Rhinovirus    : 2-4 days          :    
:...............:...................:    

^{Source: Lessler, J., Reich, N. G., Brookmeyer, R., Perl, T. M., Nelson, K. E., & Cummings, D. A. T. (2009). Incubation periods of acute respiratory viral infections: a systematic review. The Lancet. Infectious Diseases, 9(5), 291–300. http://doi.org/10.1016/S1473-3099(09)70069-6}

They all have been found to have an incubation period ranging from 2 up to 8 days. This includes "normal" infection, and I strongly doubt the strawberries will carry a lot more viruses than standard infections (see below). Only 5% of cases will have an incubation period shorter than 20 hours. Because they are distributed normally, it is very unlikely to have an incubation period of 3-6 hours, which is what you described.

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It is important to wash all fruit and vegetables before you eat them to ensure they are clean and safe to eat. Most people are aware of the importance of handling meat safely, but many consider the risk of food poisoning from vegetables to be low. "It's a myth that a little bit of dirt doesn't do you any harm," says Dr Andrew Wadge, chief scientist of the Food Standards Agency (FSA). "Soil can sometimes carry harmful bacteria and, although food producers have good systems in place to clean vegetables, the risk can never be entirely eliminated."

^{Source: NHS.uk}

In the EU, imported fruits have a lot of regulations to match, and that they travel from the supplier to the consumer without being cleaned once is highly unlikely (still does happen sometimes, but highly unlikely). Because the gems can be quite devastating and infectious, on should always clean vegetables to prevent those to spread, but it doesn't seem too dangerous missing one out.

Also, think about exponential growth. If the amount of viruses in your body were doubled every 2 hours (I don't have any numbers for that, but anything above seems unlikely), and your incubation time was 30 hours earlier than expected, you would have to have taken in 2¹⁵ more viruses than the normally infected.

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Most important:

Since the virus is sensitive to pH and temperature, it replicates best below core body temperature and does not survive the acids found in the stomach, which means the virus does not infect the lower respiratory or gastrointestinal tract.

^{Source: Morgridge Institute for Research}

This makes it even more unlikely, because the virus only has time to reach the nasal area until you've swallowed it.

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Bottom line: Think about yesterday or the day before. With whom did you shake hands and touched your face afterwards without washing your hands? Who did you stand next to that had a running nose?