%
%          SIR_rhs2
%
  function dy = SIR_rhs2(t,y,params);

  global N

  beta = params(1);
  gamma = params(2);
  mu = 0;

  S = y(1);
  I = y(2);

%
  dy = [mu*(N-S) - beta*I*S;
        beta*I*S - (gamma+mu)*I];
%