How fast does a virus spread from one person to another is still a puzzle to scientists. They use a model whose number is a basic reproduction number R which on average tells you howmany people an infected person can infect. But what exactly is R0?

R0 measures how fast a virus is spreading. It indicates the average number of people who can be contaminated by an infected person.

The R0 rating is calculated using three factors: the length of time an infected person is contagious, the number of contacts per day; and the risk of virus transmission during contact.

For a virus to decline and disappear, the R number must be kept below one. This makes it possible to break the transmission chain.

If the R rating is equal to one, the disease lingers without an outbreak.

This report was produced by Mwanzo TV with the support of Code for Africa and Deutsche Welle Akademie Kenya