size(9cm,10cm,IgnoreAspect); pair d=(1,0.25); real s=1.6d.x; real y=0.6; defaultpen(fontsize(8pt)); picture box(string s, pair z=(0,0)) { picture pic; draw(pic,box(-d/2,d/2)); label(pic,s,(0,0)); return shift(z)*pic; } label("Birds",(0,y)); picture removed=box("Removed ($R_B$)"); picture infectious=box("Infectious ($I_B$)",(0,-1.5)); picture susceptible=box("Susceptible ($S_B$)",(0,-3)); add(removed); add(infectious); add(susceptible); label("Mosquitoes",(s,y)); picture larval=box("Larval ($L_M$)",(s,0)); picture susceptibleM=box("Susceptible ($S_M$)",(s,-1)); picture exposed=box("Exposed ($E_M$)",(s,-2)); picture infectiousM=box("Infectious ($I_M$)",(s,-3)); add(larval); add(susceptibleM); add(exposed); add(infectiousM); path ls=point(larval,S)--point(susceptibleM,N); path se=point(susceptibleM,S)--point(exposed,N); path ei=point(exposed,S)--point(infectiousM,N); path si=point(susceptible,N)--point(infectious,S); draw(minipage("\flushright{recovery rate ($g$) \& death rate from virus ($\mu_V$)}",40pt),point(infectious,N)--point(removed,S),LeftSide,Arrow, PenMargin); draw(si,LeftSide,Arrow,PenMargin); draw(minipage("\flushright{maturation rate ($m$)}",50pt),ls,RightSide, Arrow,PenMargin); draw(minipage("\flushright{viral incubation rate ($k$)}",40pt),ei, RightSide,Arrow,PenMargin); path ise=point(infectious,E)--point(se,0.5); draw("$(ac)$",ise,LeftSide,dashed,Arrow,PenMargin); label(minipage("\flushleft{biting rate $\times$ transmission probability}",50pt),point(infectious,SE),dir(-60)+S); path isi=point(infectiousM,W)--point(si,2.0/3); draw("$(ab)$",isi,LeftSide,dashed,Arrow,PenMargin); draw(se,LeftSide,Arrow,PenMargin); real t=2.0; draw("$\beta_M$", point(susceptibleM,E){right}..tension t..{left}point(larval,E), 2*(S+SE),red,Arrow(Fill,0.5)); draw(minipage("\flushleft{birth rate ($\beta_M$)}",20pt), point(exposed,E){right}..tension t..{left}point(larval,E),2SW,red, Arrow(Fill,0.5)); draw("$\beta_M$", point(infectiousM,E){right}..tension t..{left}point(larval,E),2SW, red,Arrow(Fill,0.5)); path arrow=(0,0)--0.75cm*dir(35); draw(point(larval,NNE), Label(minipage("\flushleft{larval death rate ($\mu_L$)}",45pt),1), arrow,blue,Arrow); draw(point(susceptibleM,NNE), Label(minipage("\flushleft{adult death rate ($\mu_A$)}",20pt),1), arrow,N,blue,Arrow); draw(point(exposed,NNE),Label("$\mu_A$",1),arrow,blue,Arrow); draw(point(infectiousM,NNE),Label("$\mu_A$",1),arrow,blue,Arrow);