How many?

Nanometres

The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American spelling) is a unit of length in the metric system, equal to one billionth (short scale) of a metre (0.000000001 m). To demonstrate just how small a nanometre is, it is commonly used to measure atoms and molecules. A typical virus is around 100 nanometres wide. The coronavirus, known as COVID 19 is believed to be between 60 to 120 nanometres wide.

Hands

The hand is a unit of measurement of length standardized to 4 in (101.6 mm). It is used to measure the height of horses in many English-speaking countries, including Australia, Canada, the Republic of Ireland, the United Kingdom, and the United States. It was originally based on the breadth of a human hand. The average shire horse is 16 to 17 hands tall and can even reach up to 18 hands.