Who would like to explain the meaing of "1·1"?

Context:

Assuming a borderline effective reproduction number R of 1·1, we expect to see C(Rn+1—1)/(R—1) cases of acute flaccid paralysis within n transmission generations. It might take more than 30 generations of 10 days5—nearly 1 year of silent transmission—before one acute flaccid paralysis case is identified and an outbreak is detected, although hundreds of individuals would carry the infection. Vaccinating only Syrian refugees—as has been recommended by the European Centre for Disease Prevention and Control6—must be judged as insufficient; more comprehensive measures should be taken into consideration. Oral polio vaccination provides high protection against acquisition and spreading of the infection, but this vaccine was discontinued in Europe because of rare cases of vaccination-related acute flaccid paralysis. Only some of the European Union member states still allow its use and none has a stockpile of oral polio vaccines.2 Routine screening of sewage for poliovirus has not been done in most European countries,2 but this intensified surveillance measure should be considered for settlements with large numbers of Syrian refugees.

More:

http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(13)62220-5/fulltext