WORLD HEALTH ORGANIZATION ORGANISATION M O N D I A L E D E L A SANTÉ EXPERT COMMITTEE ON YELLOW FEVER Entebbe, 9-15 March 1971
V I R / V F / 7 1 .13
ORIGINAL:
FRENCH
INDEXED
EARLY RECOGNITION OF SUSPECTED CASES
by Dr P. Brès Virus Diseases S e r v i c e
When he e n c o u n t e r s an i n i t i a l y e l l o w f e v e r c a s e a d o c t o r o f t e n h e s i t a t e s b e f o r e r e a c h i n g t h i s d i a g n o s i s because o f t h e economic o r even p o l i t i c a l consequences w h i c h may r e s u l t . However, any d e l a y c a n be s e r i o u s s i n c e i t may a l l o w a s e v e r e epidemic t o d e v e l o p . In such c i r c u m s t a n c e s , t h e d o c t o r has need o f t h e c e r t a i n t y w h i c h can be g i v e n by l a b o r a t o r y t e s t s . On t h e o t h e r hand, once t h e e x i s t e n c e o f an e p i d e m i c has been r e c o g n i z e d , i t i s e s s e n t i a l t o d e t e c t as many cases as p o s s i b l e , even a t t h e r i s k o f b e i n g o v e r - z e a l o u s , i n an e f f o r t t o determine the a c t u a l extent o f the epidemic. These two o p p o s i n g a t t i t u d e s l e a d t o a d i f f e r e n t use o f t h e c l i n i c a l c r i t e r i a and l a b o r a t o r y t e s t s i n t h e d e t e c t i o n o f s u s p e c t e d c a s e s . Clinical criteria i n a patient with or
For t h e e p i d e m i o l o g i s t , a d i a g n o s i s o f y e l l o w f e v e r may be reached without jaundice. Yellow fever diagnosis i n a p a t i e n t w i t h jaundice
In t h e s e r i o u s form o f y e l l o w f e v e r , j a u n d i c e appears o n l y a t t h e commencement o f t h e t h i r d stage, the p e r i o d of t o x i c r e a c t i o n which f o l l o w s the i n i t i a l fever o r stage o f congestion and t h e i n t e r m e d i a t e " p e r i o d o f c a l m " when t h e r e i s a temporary r e m i s s i o n . Jaundice i s , i n f a c t , r a r e l y v e r y marked; i t commences by a y e l l o w i s h t i n g e o f t h e s c l e r a l and g r a d u a l l y d e v e l o p s , sometimes becoming e v i d e n t o n l y a f t e r d e a t h o r d u r i n g c o n v a l e s c e n c e . The haemorrh a g i c s i g n s and, i n p a r t i c u l a r , v o m i t i n g o f b l o o d ("black v o m i t " ) a r e more c h a r a c t e r i s t i c ; e s p e c i a l l y i f they l e a d t o d e a t h i n l e s s than n i n e days w i t h a c l i n i c a l p i c t u r e w h i c h i s sometimes c o m p l i c a t e d by symptoms o f e n c e p h a l i t i s . O t h e r t y p e s o f j a u n d i c e q u i t e f r e q u e n t i n t h e t r o p i c s must be d i s t i n g u i s h e d from y e l l o w fever; I n f e c t i o u s h e p a t i t i s , wh^ch i s v e r y f r e q u e n t ; a c u t e y e l l o w a t r o p h y o f t h e l i v e r , w h i c h v e r y much r e s e m b l e s e x t r e m e l y s e r i o u s y e l l o w f e v e r ; l e p t o t , p i r a l j a u n d i c e ; and p o i s o n i n g by t e t r a c h l o r i d e o r o t h e r p o i s o n s . Diagnosis of yellow fever i n a patient without jaundice
T h i s p o s s i b i l i t y i s much more f r e q u e n t than t h e p r e c e d i n g one and i s a l s o l e s s e v o c a t i v e . I t may be t h e b e g i n n i n g o f a s e r i o u s form w h i c h w i l l s u b s e q u e n t l y emerge o r o f a m i l d form which i s very d i f f i c u l t to l a b e l . The symptoms observed d u r i n g two o r t h r e e days c o m p r i s e f e v e r , headache and backache w h i c h s e t i n suddenly - nausea, sometimes a p i s t a x i s , and a l a c k o f c o r r e l a t i o n o f p u l s e and temperature. Such symptoms h a r d l y j u s t i f y more than a d i a g n o s i s o f " s u s p e c t e d y e l l o w f e v e r " i f they o c c u r d u r i n g an e p i d e m i c .
The Issue of this document does not constitute formal publication. It should not be reviewed, abstracted or quoted without the agreement of the World Health Organization. Authors alone are responsible for views expressed in signed articles.
Ce
document ne constitue pas une publication.
Il ne doit faire l'objet d'aucun compte rendu ou résumé ni d'aucune citation sans l'autorisation de l'Organisation Mondiale de la Santé. Les opinions exprimées dans les articles signés n'engagent que leurs auteurs.
VIR/YF/71.13
page 2 There a r e many t r o p i c a l (which fever, may be a s s o c i a t e d w i t h smallpox tests o f the c l i n i c a l criteria good use must b e made o f l a b o r a before d i s e a s e s which may p r e s e n t yellow fever), the same c l i n i c a l picture: malaria
dengue, r e l a p s i n g
tick-borne f e v e r ,
blackwater
t h e r a s h and v a r i o u s a r b o v i r u s e s .
Laboratory
Because o f the u n c e r t a i n n a t u r e tory tests, suitably
s e l e c t e d a c c o r d i n g t o t h e s t a g e o f the d i s e a s e . from the blood i s fairly easy d u r i n g the f i r s t day. 1955). to i n t e r p r e t . The t h r e e days and more
I s o l a t i o n of the v i r u s difficult afterwards, been a c h i e v e d The presence
but s t i l l
p o s s i b l e up t o t h e s e v e n t h a liver
S u c c e s s f u l i s o l a t i o n has
on the t w e l f t h day from for specific
sample (Anderson
results of tests
a n t i b o d i e s a r e sometimes d i f f i c u l t
o f such a n t i b o d i e s i n t h e b l o o d d u r i n g the f i r s t fever infection.
t h r e e days e x c l u d e s
the p o s s i b i l i t y
of a current yellow
T h e i r absence from A positive
the b l o o d d u r i n g conversion.
the t h i r d week a l s o Previous
justifies
a negative diagnosis. an e a r l y group B sample arbo-
result with convalescent
serum has no s i g n i f i c a n c e (Theiler 1958),
i f comparison w i t h
does n o t show s e r o l o g i c a l
c o n t a c t w i t h one o r more o t h e r
v i r u s e s makes i n t e r p r e t a t i o n v e r y d i f f i c u l t In most c a s e s biopsy histopathological
tests w i l l
g i v e the q u i c k e s t r e p l y
- in less
than Liver
48 puncture
hours - b u t they may g i v e r i s e
t o e r r o r s and c a l l
f o r c o n s i d e r a b l e competence.
i s c o n t r a - i n d i c a t e d b e c a u s e o f the danger o f haemorrhage. usual laboratory tests f o r h e p a t i t i s do n o t c o n t r i b u t e a n y t h i n g i s always found i n the benign ones. specific from to yellow
The in in
fever diagnosis. does n o t e x c l u d e the t r o p i c s ,
I n c r e a s i n g and pronounced a l b u m i n u r i a the p o s s i b i l i t y
t h e t h i r d day are frequent
the s e r i o u s forms b u t i s l a c k i n g
Absence o f a l b u m i n u r i a , t h e r e f o r e , of albuminuria
o f y e l l o w f e v e r and o t h e r c a u s e s (MacNamara 1957).
f o r example b i l h a r z i a s i s
Organization of epldemiolopfical screening The possible. A f r i c a WHO of c o - o r d i n a t i o n of c l i n i c a l and l a b o r a t o r y t e s t s n e c e s s i t a t e s , i n v i e w cases s e r v i c e was e s t a b l i s h e d i n B r a z i l
•• ' ' o f the s i z e In of .
the endemic a r e a s , an o r g a n i z a t i o n f o r t h e c o n f i r m a t i o n o f s u s p e c t e d In t h e A m e r i c a s a v i s c e r o t o m y has o r g a n i z e d a permanent s u r v e i l l a n c e
a s r a p i d l y as i n 1930.
system, and emergency a s s i s t a n c e i n t h e e v e n t
epidemics. At the n a t i o n a l l e v e l , t h e s u r v e i l l a n c e system i s b a s e d on t h e v i g i l a n c e i n sentinal hospitals, from situated cases fever. Samples taken suspected o f the personnel particularly to the
o f the mobile exposed national
h e a l t h teams and o f d o c t o r s
i n areas a r e sent
to t h e r i s k o f y e l l o w
l a b o r a t o r y which i s i n l i a i s o n w i t h t h e WHO
Regional Reference
Centres
f o r Arboviruses,
where t h e r e s u l t s c a n be c o n f i r m e d
and r e s e a r c h c o m p l e t e d .
The R e g i o n a l R e f e r e n c e C e n t r e s have a team which i s a v a i l a b l e a t s h o r t n o t i c e f o r commencing an e p i d e m i o l o g i c a l i n v e s t i g a t i o n a t t h e s i t e o f an e p i d e m i c w h i l e a w a i t i n g t h e e s t a b l i shment o f o t h e r teams on t h e s p o t . The team i n c l u d e s an e p i d e m i o l o g i s t , a v i r o l o g i s t and Intomoloeist The p r o b a b i l i t y o f t h e c a s e s s c r e e n e d b e i n g y e l l o w f e v e r o n e s i n c r e a s e s a c c o r d i n g To Z Z r tLy have been d e t e c t e d by i n t e r r o g a t i o n o f t h e i n h a b i t a n t s , e x a m i n e d by m e d i c a l Ma^es auxiliaries Clinical examined by d o c t o r s w i t h o u t l a b o r a t o r y t e s t s o r c o n f i r m e d i n examine y i n c r e a s i n g l y probable i n accordance ^''°^„dice(b) f e v e r i s h j a u n d i c e w i t h a l b u m i n u r i a ; days o f the d i s e a s e . — ^ ^ - ^ ^ ' • -y^ '-^
^^rl^'Z'T?' wxth the f o l l o w i n g C'^) f e v e r i s h "
VIR/YF/71.13
page 3 C a s e s s h o u l d be s c r e e n e d w i t h i n a f e w d a y s , u s i n g a s u f f i c i e n t n u m b e r o f t e a m s t o a s s e s s t h e p r e c i s e area of spread o f the epidemic as soon as p o s s i b l e . The n u m b e r o f c o n f i r m e d cases w i l l vary according to the d i a g n o s t i c c r i t e r i a a p p l i e d . A s e r o l o g i c a l s u r v e y may b e i n d i c a t e d t o evaluate the r e a l i n t e n s i t y o f t h e c i r c u l a t i o n o f the v i r u s , t a k i n g i n t o account s u b c l i n i c a l forms. The m o r t a l i t y r a t e i s u s u a l l y 5 t o 10 p e r c e n t , o f a l l c a s e s a n d , a s e a r l y as 1907, C a r r o l e s t a b l i s h e d t h a t i t s h o u l d n o t exceed 20-25 p e r c e n t , and t h a t a h i g h e r r a t e showed t h a t t h e b e n i g n c a s e s had gone u n d e t e c t e d .
REFERENCES
A n d e r s o n , C. R . e t a l . ( 1 9 5 5 ) T r a n s , r o y . S o c . t r o p . Med. MacNamara, Theiler, F. N . ( 1 9 5 7 ) W. A f r . med. ( 1 9 5 8 ) J . Amer. J . , 6, 137-146
Hyg.. 49, 580-581
M. & C a s a l s
J . t r o p . Med. H y g . ,
585-594
WORLD HEALTH
ORGANIZATION
VIflAF /71.13 Add.l ENGLISH ONLY INDEXED
ORGANISATION M O N D I A L E D E L A SANTÉ EXPERT COMMITTEE ON YELLOW FEVER Entebbe. 9-15 March 1^71 Methods of s u r v e i l l a n c e f o r yellow f e v e r EARLY RECOGNITION OF SUSPECTED CASES by P. Brès, M.D., V i r u s Diseases O r g a n i z a t i o n of e p l d e m i o l c e l c a l screeninp (continued)
Cases should be detected w i t h i n a few days, using a s u f f i c i e n t number of teams to a s s e s s the p r e c i s e area of the spread of the epidemic as soon as p o s s i b l e . Suspected cases a r e found by door-to-door i n v e s t i g a t i o n o r through d i s p e n s a r i e s and h o s p i t a l r e g i s t e r s . The quickness i n the evaluation of suspected cases i s more important than i t s accuracy and t h e i r l o c a t i o n w i l l determine p r i o r i t i e s i n v a c c i n a t i o n and c o n t r o l o f v e c t o r s . A s e r o l o g i c a l survey i s indicated t o evaluate the a c t u a l i n t e n s i t y of the transmission o f the v i r u s by i n c l u d i n g s u b c l i n i c a l forms. The use o f microtechniques w i l l save time and reagents. The CF t e s t w i l l screen recent i n f e c t i o n s which u s u a l l y give a t i t r e equal o r above 1:32. I f time and other antigens i n group B are a v a i l a b l e , the homotyplc o r h e t e r o t y p l nature of the CF antibodies may be assessed. In primary i n f e c t i o n , the CF antibodies appear and increase around the tenth day, s l i g h t l y a f t e r the HI a n t i b o d i e s ; i n secondary i n f e c t i o n s they increase around the second t o t h i r d days. The sampling of the population w i l l be d i r e c t e d to get information on the d i s t r i b u t i o n of cases according t o age-group and sex. Serum samples w i l l be taken among epidemic s u r v i v o r s , a c u t e l y i l l persons and some of those who have no h i s t o r y of recent i l l n e s s . The date thus obtained could be f r u i t f u l l y compared w i t h a previous survey, i f i t has been done, o r w i t h a second survey a f t e r the end of the outbreak. I f time and personnel are a v a i l a b l e , a comparative s e r o l o g i c a l survey may be done i n an adjacent area supposed t o be free o f i n f e c t i o n , o r some sera could be taken arotind the estimated focus t o a s c e r t a i n the l i m i t s o f propagation of the epidemic. I n t e r p r e t a t i o n of data The number o f suspected cases t o take i n t o account w i l l vary according t o the diagnostic c r i t e r i a a p p l i e d . The number of confirmed cases i s given by the l a b o r a t o r y r e s u l t s : h i s t o p a t h o l o g y , i s o l a t i o n o f the v i r u s o r conversion i n paired sera. P o s i t i v e s i n g l e sera may a l s o be considered as confirmed cases of yellow fever i f h e t e r o t y p i c antibodies are absent. Chronology o f cases w i l l show the apparent onset o f the epidemic, the r e a l onset and the peak which may take place a t d i f f e r e n t times i n d i f f e r e n t p l a c e s . Histograms o f age groups and sex w i l l show a p a t t e r n of epidemicity o r recrudescence of endemicity. S e r o l o g i c a l r e s u l t s w i l l allow t o c a l c u l a t e the i n f e c t i o n rate {% p o s i t i v e / t e s t e d ) and the sampling o f sera would be representative of the population, t h i s w i l l determine the estimated number of persons who c i r c u l a t e d the v i r u s . The c l i n i c a l i n f e c t i o n r a t e (% of p o s i t i v e w i t h I l l n e s s / t e s t e d ) and the death rate (% o f p o s i t i v e who died/tested) e x t r a p o l a t e d t o the t o t a l population, w i l l give an estimate of the t o t a l c l i n i c a l cases and deaths. The issue of this document does not constitute Ce document ne constitue pas une publication, formal publication. It should not be reviewed, II ne doit faire l'objet d'aucun compte rendu ou abstracted or quoted without the agreement of résumé ni d'aucune citation sans l'autorisation de the World Health Organization. Authors alone l'Organisation Mondiale de la Santé. Les opinions are responsible for views expressed in signed exprimées dans les articles signés n'engagent articles. que leurs auteurs.
VIB/YIV71.13 Add.l page 2 A statement by Jarr.es C a r r o l l In 1907 i s always t r u e : "Under f a v o u r a b l e c o n d i t i o n s t h e m o r t a l i t y r a t e from y e l l o w f e v e r s h o u l d n o t exceed 10 o r I 5 p e r c e n t ; i t s h o u l d never exceed 20 o r 25 p e r c e n t under any c i r c u m s t a n c e s , and a h i g h e r death r a t e would w a r r a n t the s u s p i c i o n t h a t t h e m i l d e r c a s e s were e s c a p i n g r e c o g n i t i o n . "