Question: dsolve for systems of differential equations

Hi, Could some body help me here, Am trying to use dsolve to solve the following system of equations but I am getting the following error

difS := diff(w(t), t) = nu+delta*z(t)-(1/100)*psi*w(t)*(x(t)+epsilon*y(t))-mu*w(t);

difI := diff(x(t), t) = (1/100)*(1-rho)*psi*w*(x(t)+epsilon*y(t))+PI*y(t)-h[1]*x(t);

difC := diff(y(t), t) = (1/100)*rho*psi*w*(x(t)+epsilon*y(t))+(1-q)*eta*x(t)-h[2]*y(t);

difR := diff(z(t), t) = q*eta*x(t)+beta*y(t)-(mu+delta)*z(t)

sys := dsolve({difC, difI, difR, difS, w(0) = 90, x(0) = 9, y(0) = 1, z(0) = 0}, {w(t), x(t), y(t), z(x)}, type = numeric, output = listprocedure) error:

Error, (in dsolve/numeric/process_input) indication of the unknown(s) of the problem {w(t), x(t), y(t), z(x)} disagrees with input system {w(t), x(t), y(t), z(t)}

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