This is easily achieved using the pivot_longer function. Example on toy data similar to your current data below.
library(tidyverse)
patients <- tibble(
country = c("Afghanistan", "Algeria", "Andorra"),
date1 = c(0,0,0),
date2 = c(1,1,1),
date3 = c(0,0,0),
date_n = c(1,1,1)
)
pivot_longer(patients, -country, names_to = "date", values_to = "recovered_patients")
#> # A tibble: 12 × 3
#> country date recovered_patients
#> <chr> <chr> <dbl>
#> 1 Afghanistan date1 0
#> 2 Afghanistan date2 1
#> 3 Afghanistan date3 0
#> 4 Afghanistan date_n 1
#> 5 Algeria date1 0
#> 6 Algeria date2 1
#> 7 Algeria date3 0
#> 8 Algeria date_n 1
#> 9 Andorra date1 0
#> 10 Andorra date2 1
#> 11 Andorra date3 0
#> 12 Andorra date_n 1
Created on 2021-10-25 by the reprex package (v2.0.1)