Error using feval and in odearguments?

if true
  % code
endI'm trying to simulate the SEIR model for dengue fever using the following differential equations:
function ypseir =ypseir(t,y)
u=0.0045
N=5535002
S=5535002
E=50
I=50
J=0
R=0
v=0.0045
B=0.375
o=1/8.5
z=1/6
ypseir(1) = u*N-((B*(J/N))+u)*S
ypseir(2) = ((B *(J/N))*S)-(u+o)*E
ypseir(3) = o*E+(u+z)*I
ypseir(4) = z*I-u*R
ypseir = [ypseir(1) ypseir(2) ypseir(3) ypseir(4)]';
to = 0;
tf =100;
yo = [5535002 50 50 0];
[t y] = ode45('ypseir',[to tf],yo);
plot(t,y(:,1),t,y(:,2),t,y(:,3),y(:,4))
title('Human Population Without Control')
xlabel('time')
ylabel('susceptible, exposed, infected, recovered')
And I'm presented with the following errors: Error using feval Maximum recursion limit of 500 reached.
Error in odearguments (line 87) f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.
Truthfully I'm unsure how to use MATLAB and compute the SEIR model.
Help is needed! Thank you!.
Help is needed! Thank you!