chapter 6 eisenman lecture

8/19/2019 Chapter 6 Eisenman Lecture

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CHAPTER 6TRANSMISSION OF INFECTION, THE

COMPROMISED HOST AND EPIDEMIOLOGY

Flea

Tick

nopheles mosquitoTsetse Fly

Triatoma (kissing bug)

http://www.centreguigues.org/wp-content/uploads/2010/08/Anopheles-Mosquitoes.jpghttp://animals.howstuffworks.com/insects/insect-pictures.htm


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WHY IS THIS IMPORTANT?

• Understandn! t"e #$de $% trans#ss$n %$r a!&en dsease and s's(e)t*+t $% t"e "$st are&ta+ %$r de&e+$)n! #et"$ds t$ )re&ent t"e s)read$% dsease-


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O.ER.IEW


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TRANSMISSION OF INFECTION

• T"e trans#ss$n /s)read0 $% n%e(t$n s t"e

%na+ re1're#ent %$r a s'((ess%'+ n%e(t$n-

• T2$ %a(t$rs a%%e(t t"e s)read $% n%e(t$n3

4 Reser&$rs $% n%e(t$'s $r!ans#s 4 )+a(es 2"ere

)at"$!ens (an !r$2 and a(('#'+ate

4 Me("ans#s $% trans#ss$n 4 t"e &ar$'s 2as n

2"(" )at"$!ens #$&e %r$# )+a(e t$ )+a(e-


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PATHOGEN RESER.OIRS

• T"ere are t"ree )$tenta+ reser&$rs $%

)at"$!ens3

4 H'#ans

4 Ot"er an#a+s

4 N$n+&n! reser&$rs


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HUMAN RESER.OIRS

• T"ere are t2$ t)es $% "'#an reser&$r3

4 S(5 )e$)+e 4 S#)t$#at( nd&d'a+s are eas+

dent%ed-

4 Ma *e d%%('+t t$ dent% 2"en s#)t$#s "a&e

et t$ de&e+$) $r "a&e (eased-

4 Carrers $% n%e(t$ns 4 nd&d'a+s 2"$ 2++ ne&ers"$2 s#)t$#s *'t are st++ n%e(t$'s-


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ANIMAL RESER.OIRS

• Dseases trans%erred %r$# an#a+s t$ "'#ansare (a++ed $$n$t( dseases-

• 7$$n$t( dseases (an *e trans#tted t"r$'!"3

Dre(t ($nta(t 2t" "'#ans /*tes, s(rat("es, et(-0

Indre(t ($nta(t /2aste #atera+ $% a +tter *$8, %'r,%eat"ers, $r n%e(ted #eats0-

Indre(t+ trans#tted * &e(t$rs-


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ANIMAL RESER.OIRS


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NONLI.ING RESER.OIRS

• N$n+&n! reser&$rs $% n%e(t$n n(+'de

2ater, %$$d, and s$+- 4 Water s t"e #$st dan!er$'s-

• In%e(t$ns $% t"s 5nd are $%ten seen n

($'ntres 2t" )$$r santat$n and +$2 +e&e+s$% )ers$na+ "!ene-


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NONLI.ING RESER.OIRS

• We (ann$t +&e 2t"$'t 2ater and as a res'+t,re!$ns 2t" )$$r santat$n )ra(t(es (an "a&e"!" +e&e+s $% %e(a+ ($nta#nat$n n t"e 2ater- 4 T"s +eads n%e(t$n t$ s)read &a t"e %e(a+9$ra+

r$'te $% n%e(t$n-

• F$$d ($nta#nat$n s $%ten a )r$d'(t $%

nat'ra+ s)$+a!e-• Pat"$!ens %$'nd n s$+ !enera++ re1're t"e

s5n t$ *e *r$5en %$r entr nt$ t"e *$d-


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MECHANISMS OF TRANSMISSION

• T"ere are t"ree #$des $% )at"$!en

trans#ss$n3

4 C$nta(t trans#ss$n

4 .e"(+e trans#ss$n

4 .e(t$r trans#ss$n


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CONTACT TRANSMISSION• A "$st s e8)$sed t$ n%e(t$'s a!ents * #a5n! ($nta(t

2t" t"e a!ent $r te#s ($nta#nated 2t" t"e )at"$!en

s$ t (an rea(" a )$rta+ $% entr nt$ t"e "$st-

T"ere are t"ree t)es $%

($nta(t trans#ss$n3•Dre(t ($nta(t•Indre(t ($nta(t •Dr$)+et


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DIRECT CONTACT

TRANSMISSION

• T"ere s n$ nter#edar *et2een n%e(ted and'nn%e(ted nd&d'a+s-

• It en($#)asses s'(" t"n!s as t$'("n!, 5ssn!, andse8'a+ ntera(t$ns-

• Dseases trans#tted t"r$'!" dre(t ($nta(t n(+'de3 4 He)atts A

4 S#a++)$8

4 Sta)"+$($((a+ n%e(t$ns

4 M$n$n'(+e$ss

4 Se8'a++ trans#tted dseases-


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INDIRECT CONTACT TRANSMISSION

• Ta5es )+a(e t"r$'!" nter#edates3 4 Tss'es, Hand5er("e%s

4 T$2e+s 4 :eddn! 4 C$nta#nated need+es /t"e +atter eas+ trans%errn! HI. and

"e)atts :0-

• N$n+&n! nter#edates t"at a(t as t"e a!ents $%trans#ss$n * ndre(t ($nta(t are re%erred t$ as %$#tes,&e"(+es %$r trans#ss$n-


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DROPLET TRANSMISSION

• Dr$)+et trans#ss$n s seen n t"e trans%er $%

res)rat$r dseases s'(" as n%+'ena and

2"$$)n! ($'!"-

• It (an $(('r t"r$'!" sneen!, ($'!"n!, and

e&en +a'!"n!-


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.EHICLE TRANSMISSION

• .e"(+e trans#ss$n n&$+&es )at"$!ens rdn! a+$n! $ns'))$sed+ (+ean ($#)$nents-

• E8a#)+es $% &e"(+es n(+'de3

4 Ar

4 F$$d

4 Water

4 :+$$d

4 :$d+ %+'ds

4 Dr'!s

4 Intra&en$'s %+'ds


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.EHICLE TRANSMISSION

• Ar s a d%%('+t &e"(+e t$ ($ntr$+-

4 D'st 'ses ar as a &e"(+e and (an ($ntan "'!e

n'#*ers $% )at"$!ens-

4 M(r$*a+ s)$res and %'n!a+ s)$res (an a+s$ 'se ar

t$ tra&e+ %r$# "$st t$ "$st-


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.ECTOR TRANSMISSION

• Pat"$!ens are trans#tted * (arrers, 's'a++

art"r$)$ds3

4 F+eas

4 T(5s

4 F+es

4 L(e

4 M$s1't$es


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.ECTOR TRANSMISSION

T"ere are t2$ t)es $% &e(t$r

trans#ss$n3

• Me("an(a+ &e(t$r 4 )at"$!ens are $n&e(t$r;s *$d )arts and are )ass&e+

*r's"ed $%% and $nt$ t"e "$st

• :$+$!(a+ &e(t$r 4 )at"$!ens are

2t"n t"e &e(t$r and trans#ss$n t$t"e "$st s t"r$'!" a *te-


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FACTORS AFFECTING DISEASE


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FACTORS AFFECTING DISEASETRANSMISSION

• T"e $&era++ "ea+t" $% t"e "$st "as a (+ear n%+'en(e $nt"e dsease )r$(ess-

• F$r a++ )e$)+e, t"e dsease )r$(ess s a%%e(ted *3

I##'ne C$#)eten(e < Hea+t" Stat's

4 A!e 4 dsease +e&e+s tend t$ n(rease as 2e a!e

4 Gender 4 s$#e dseases are #$re )re&a+ent n $ne !ender $r

an$t"er

• Urnar tra(t n%e(t$ns /UTIs0 are seen #$re n 2$#en

• Pne'#$na s seen #$re n #en-

4 L%est+e3 dr'! 'se, se8'a+ $rentat$n < se8'a+ )ra(t(es



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TRANSMISSION

• O((')at$n 4 #$re n%e(t$ns are seen n "ea+t" (are 2$r5ers-

• Med(at$n3 I##'n$s'))resants, ("e#$t"era), radat$n

• E#$t$na+ state 4 a &'+nera*+e e#$t$na+ state (an de(rease

##'n$($#)eten(e n t"e "$st- War < Stress

• C+#ate 4 t a))ears t"at t"ere s a !reater n(den(e $%

res)rat$r n%e(t$ns n ($+der (+#ates-

• Det 4 Ma+n'trt$n, a+($"$+s#, )arastes

• En&r$n#ent3 L$(at$n, s'n+!"t, )$++'t$n, et(-

• Genet( Preds)$st$n


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HERD IMMUNITY

• Herd ##'nt arses 2"en a #a=$rt $% a )$)'+at$n /"erd0 s ##'ne t$ an n%e(t$n t"ere are

&er %e2 )$tenta+ "$sts and t"e dsease essenta++dsa))ears-

•It s ($n%erred t"r$'!"&a((nat$n $r nat'ra+ ##'nt

arsn! %r$# )re&$'s e8)$s're-

•C'rrent e8a#)+es $% "erd

##'nt n(+'de )$+$ and#eas+es-

•Herd ##'nt 'sed t$

erad(ate S#a++)$8-

Herd Immunity


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Herd Immunity

Duration(D)

length of infectious period

Infectivity(I)

Measure of transmissability

Number of susceptibles(s)

in the population

Herd ImmunityDepends on 3 factors

Triple product = sID

A threshold sID exists for each potential epidemic situation, below which anepidemic is unlikely.

PORTALS OF E>IT


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PORTALS OF E>IT

• Man )$rta+s $% e8t are dent(a+ t$t"e )$rta+s $% entr-

• Pat"$!ens 'se t"ese t$ e8t %r$# a"$st-

• E8tn! s 's'a++ a("e&ed t"r$'!"3

Se(ret$ns3 sa+&a, s)'t'#, andres)rat$r dr$)+ets-

E8(ret$ns3 Urne < %e(es

:$d+ %+'ds3 *+$$d, CSF, &a!na+se(ret$ns, se#en, et(-

THE COMPROMISED HOST


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THE COMPROMISED HOST

• T"e "$st;s a*+t t$ #$'nt a de%ense s re%erred t$ as ts

##'n$($#)eten(e-• I##'n$($#)r$#sed nd&d'a+s "a&e !reater s's(e)t*+t

t$ n%e(t$n and !reater rs5 %$r se&ere n%e(t$ns-

• AIDS•Genetic immunodeficiency diseases•ndergoing c!emot!era"y# or

utili$ing immunosu""ressant drugs

•Surgical# trans"lant# and burn"atients•%remature and ne&born infants•Healt! care &orkers•T!e elderly

http://www.wired.com/entertainment/theweb/multimedia/2006/04/70622


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NEUTROPENIA

• Ne'tr$)ena s de%ned as +$2er9t"an9n$r#a+n'#*ers $% ne'tr$)"+s n t"e *+$$d3 4 Ne'tr$)"+s are a %$r# $% )r#ar )"a!$(t( de%ense

and an #)$rtant ($#)$nent $% a "$st;s nnate ##'neres)$nse-

• T"e #$st ($##$n (a'se $% )r$%$'nd ne'tr$)enas t"e ad#nstrat$n $% (t$t$8( ("e#$t"era) %$r

t"e treat#ent $% #a+!nant t'#$rs seen n (an(er-• T"e t)es $% n%e(t$ns seen 2t" ne'tr$)ena are

)r#ar+ *a(tera+ and %'n!a+-


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NEUTROPENIA

• :a(tera+ n%e(t$ns (an *e!n as s$$n as

ne'tr$)"+ +e&e+s dr$)-

• F'n!a+ n%e(t$ns are 's'a++ $n+ seen a%ter

ne'tr$)"+ +e&e+s "a&e *een +$2 %$r a

)r$+$n!ed )er$d $% t#e-

4 T"ese n%e(t$ns are $%ten ass$(ated 2t" s'r!(a+

)r$(ed'res and (at"eterat$n-


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ORGAN TRANSPLANTATION

• T"e ##'ne sste# re($!nes t"e d%%eren(es *et2een "$st $r!ans and trans)+anted $r!ans- 4 Re=e(t$n $% trans)+anted $r!ans s s'))ressed t"r$'!"

t"e ad#nstrat$n $% ##'n$s'))ressant dr'!s- 4 T"ese dr'!s red'(e re=e(t$n *'t (a'se n(reased

s's(e)t*+t t$ n%e(t$n-

• In%e(t$ns n $r!an9trans)+ant )atents re1're

treat#ent 2t" *r$ad s)e(tr'# ant*$t(s- 4 Un%$rt'nate+, t"ese dr'!s (an (a'se ant*$t(

resstan(e and s')er n%e(t$ns-

:URN PATIENTS


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:URN PATIENTS• :'rn &(t#s are at rs5 *e(a'se $% t"e +$ss $%

+ar!e areas $% t"e )r#ar )"s(a+ *arrer t$n%e(t$n 4 t"e s5n-

• W"en s5n s +$st, t"ere s a !reater ("an(e $%n%e(t$n and se)t(e#a-

• Pseudomonas n%e(t$ns are a )art('+ar )r$*+e# n *'rn &(t#s *e(a'se t"s $r!ans#s &er resstant t$ #et"$ds 'sed t$ ($ntr$+

*a(tera+ !r$2t"-


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OPPORTUNISTIC INFECTIONS

• Man n%e(t$ns are (a'sed * $))$rt'nst( )at"$!ens-

• T"ese )at"$!ens (an *e )art $% t"e n$r#a+

%+$ra n $'r *$des- 4 O))$rt'nsts (an *e "ar#+ess n t"e s)e(%( areas

2"ere t"e n$r#a++ resde *'t (an de#$nstrate&r'+en(e 2"en #$&ed t$ $t"er )arts $% t"e *$d-

4 T"e *est e8a#)+e $% t"s t)e $% n%e(t$n s'rnar tra(t n%e(t$ns /UTIs0-

Commensals, Opportunists and Pathogens


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OPPORTUNISTIC INFECTIONS

• S$#e $))$rt'nst( n%e(t$ns (an *e d'e t$ t"e

+$ss $% n$r#a+ %+$ra n $'r *$des-

4 T"s t)e $% n%e(t$n (an *e d'e t$ $&er'se


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NOSOCOMIAL INFECTIONS

• An n%e(t$n a(1'red n t"e "$s)ta+ $r#ed(a+ %a(+t s (a++ed a n$s$($#a+n%e(t$n-

• N$s$($#a+ n%e(t$ns (an a%%e(t )atents and"ea+t" (are 2$r5ers-

• T"ere are a))r$8#ate+ t2$ #++$n

n$s$($#a+ n%e(t$ns n t"e Unted Statesea(" ear res'+tn! n a))r$8#ate+ @,@@@deat"s and ($sts $% $&er B *++$n-


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• T"ese t)es $% n%e(t$ns are 's'a++

ass$(ated 2t" n&as&e a))+(at$ns s'(" as3

4 Cat"eterat$n

4 In&as&e tests and s'r!er

4 .ent+at$rs


36/53


• T"e sa#e %a(t$rs 'sed 2"en ($nsdern! an$t"er t)e $% n%e(t$n a))+ t$ "$s)ta+9*$rne

n%e(t$ns- H$s)ta+s #'st ($nsder3

4 T"e s$'r(e $% t"e n%e(t$n 4 T"e #$de $% trans#ss$n $% t"e )at"$!en

4 T"e s's(e)t*+t $% t"e )atent t$ n%e(t$n

4 Pre&ent$n and ($ntr$+


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• T"e #$st ($##$n s$'r(es $% n$s$($#a+ n%e(t$ns

2t"n t"e "$s)ta+ en&r$ns are3

4 Ot"er )atents

4 H$s)ta+ sta%%

4 .st$rs

4 Unsantar ($ndt$ns

4 Water s'))+es

4 Res)rat$r e1')#ent

4 Cat"eters

T" %


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• T"e #$st ($##$n (a'ses $%n$s$($#a+ n%e(t$ns3


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• T"ese $r!ans#s are '*1't$'s n "$s)ta+s a++$&er t"e 2$r+d-

• T"e are s$ ($##$n *e(a'se t"e are eas+#$&ed %r$# )+a(e t$ )+a(e * sta%%, )atents, $r&st$rs-

• Man $% t"ese $r!ans#s are resstant t$

ant*$t(s n(+'dn! #et"(++n9resstant S.aureus /MRSA0 and &an($#(n9resstant S.aureus /.RSA0-

NOSOCOMIAL INFECTIONS3


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NOSOCOMIAL INFECTIONS3

Un&ersa+ Pre(a't$ns

• A++ #ed(a+ %a(+tes n t"e US "a&e t$ ($n%$r# t$s)e(%( !'de+nes %$r )atent (are-• T"ese )r$(ed'res n(+'de )r$t$($+s %$r "and+n! t"e

%$++$2n!3 4 :+$$d 4 Se#en 4 .a!na+ se(ret$ns 4 Tss'e s)e(#ens 4 :$d+ %+'ds

•Personal Protective

Equipment (PPE)•Safe use of sharps•Disinfection


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EPIDEMIOLOGY

• E)de#$+$! s t"e st'd $% t"e %a(t$rs and

#e("ans#s n&$+&ed n t"e %re1'en( and

s)read $% dsease and $t"er "ea+t"9re+ated )r$*+e#s-

• E)de#$+$! (an *e 'sed n$t $n+ as a t$$+ t$

st'd dsease *'t a+s$ as a 2a t$ des!n#et"$ds %$r t"e ($ntr$+ and )re&ent$n $%

dseases-


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INCIDENCE AND PRE.ALENCE

• T"e n(den(e $% a dsease s t"e n'#*er $%ne2 (ases n a set )$)'+at$n $&er a s)e(%(

)er$d-

'no&ing t!e

incidence leel gies

information on t!e

s"read of a disease*



43/53


• T"e )re&a+en(e $% a dsease s t"e t$ta+ n'#*er

$% )e$)+e n%e(ted 2t"n a s)e(%( )$)'+at$nat an !&en t#e3

'%realence

data measure

!o& seriously

and !o& long

a "o"ulationis affected by

a disease*

MOR:IDITY AND MORTALITY


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RATES

• M$r*dt rate 4 t"e n'#*er $% nd&d'a+s

a%%e(ted d'rn! a set )er$d d&ded * t"e

t$ta+ )$)'+at$n n'#*er-

• M$rta+t rate 4 t"e n'#*er $% deat"s d'e t$ a

s)e(%( dsease d&ded * t"e t$ta+ )$)'+at$n

n'#*er-


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RATES

• E)de#$+$!(a+ st'des (+ass% dseases as3 4 S)$rad( 4 $(('rrn! n rand$# #anner n$ t"reat t$ )'*+(

"ea+t" 4 Ende#( 4 dseases t"at are ($nstant+ n t"e )$)'+at$n

4 E)de#( 4 n(den(e $% a dsease s'dden+ "!"er t"ane8)e(ted

• M$r*dt and #$rta+t rates #a n(rease• T"s #a *e($#e a #$re 2des)read )'*+( "ea+t" )r$*+e#-

4 Pande#( 4 2$r+d2de e)de#(

TWO TYPES OF EPIDEMIC


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TWO TYPES OF EPIDEMIC• C$##$n s$'r(e e)de#(-

4 It arses %r$# ($nta(t 2t" ($nta#nated s'*stan(es, #$st

($##$n+ 2ater ($nta#nated 2t" %e(a+ #atera+ $r#)r$)er+ )re)ared %$$d-

4 It a%%e(ts a +ar!e n'#*ers $% )e$)+e-

4 It s'*sdes 1'(5+ 2"en t"e ($nta#nat$n s dea+t 2t"-



47/53


• Pr$)a!ated e)de#(-

4 It s a#)+%ed * )ers$n t$ )ers$n ($nta(t

4 It re#ans n t"e )$)'+at$n %$r a +$n! t#e

4 It s #$re d%%('+t t$ dea+ 2t" t"an a ($##$n

s$'r(e $'t*rea5-


48/53

TYPES OF EPIDEMIOLOGICAL

STUDY

• T"ere are t2$ t)es $% e)de#$+$!(a+ st'd3 4 Des(r)t&e

4 Ana+t(a+


49/53


STUDY

• A des(r)t&e st'd s ($n(erned 2t" t"e )"s(a+as)e(ts $% )atents and s)read $% dsease-

• It a++$2s %$r tra(n! t"e $'t*rea5 and dent%n!t"e %rst (ase-

• A des(r)t&e st'd n(+'des3 4 Data $n a n'#*er $% (ases 4 Data $n 2"(" se!#ent $% t"e )$)'+at$n s a%%e(ted 4 Data $n t"e +$(at$n $% t"e n%e(t$n 4 Data $n t"e a!e, ra(e, #arta+ stat's, and $((')at$n $%

t"e n%e(ted )$)'+at$n-



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STUDY

• An ana+t(a+ st'd3

4 F$('ses $n esta*+s"n! t"e (a'se9and9e%%e(t re+at$ns")

4 A+2as 'ses a ($ntr$+ !r$')

4 Can *e retr$s)e(t&e $r )r$s)e(t&e

4 C$nsders %a(t$rs t"at $(('r as t"e e)de#( )r$(eeds-


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COMMUNICA:LE AND


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COMMUNICA:LE AND

CONTAGIOUS DISEASES

• S$#e dseases are ($##'n(a*+e- 4 T"e (an s)read %r$# $ne )ers$n t$ an$t"er-

• S$#e dseases are n$t ($##'n(a*+e- 4 T"e (ann$t s)read %r$# $ne )ers$n t$ an$t"er and s#)+re#an 2t"n t"e n%e(ted "$st-

• S$#e ($##'n(a*+e dseases are eas+ s)read %r$#

)ers$n t$ )ers$n and t"ese are re%erred t$ as *en!($nta!$'s-

C$ntr$+ %$r C$##'n(a*+e and C$nta!$'s Dseases


53/53

C$ntr$+ %$r C$##'n(a*+e and C$nta!$'s Dseases

• Frst #et"$d 4 Is$+at$n3

4 Pre&ents an n%e(ted nd&d'a+ %r$# "a&n! ($nta(t 2t" t"e

!enera+ )$)'+at$n, 's'a++ n "$s)ta+ settn!

• Se($nd #et"$d 4 'arantne3

4 E8)$sed "'#ans $r an#a+s are se)arated %r$# t"e

!enera+ )$)'+at$n

4 Lasts as +$n! as t"e s's)e(ted n('*at$n )er$d

4 L%ted 2"en s#)t$#s dsa))ear< a%ter n('*at$n )er$d

4 Rare+ 'sed t$da, d%%('+t t$ en%$r(e

• T"rd #et"$d 4 .e(t$r C$ntr$+3

4 C$ntr$+ t"e )$)'+at$n $% &e(t$rs, s'(" as #$s1't$es,

chapter 6 eisenman lecture

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