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Published Date: 2011-12-06 12:50:36
Subject: PRO/EDR> Pertussis, fatal - Chile: (BI)
Archive Number: 20111206.3541

PERTUSSIS, FATAL - CHILE: (BIO-BIO)
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Date: Mon 5 Dec 2011
Source: El Mercurio Online (Emol) [in Spanish, trans, Sr.Tech.Ed.MJ,
edited]
http://www.emol.com/noticias/nacional/2011/12/05/515678/ministerio-de-salud-y-preocupacion-por-tos-convulsiva-en-lactantes.html

Jorge Diaz, undersecretary for health, reported an anomalous situation
with the detection to date of 2030 cases of whooping cough, or
pertussis, which mainly affects infants younger than 1 year of age. In
a normal period 800 cases at most are recorded, a number that has been
largely exceeded.

To address this alarming situation, which so far in 2011 has resulted
in the deaths of 11 infants in the Bio-Bio Region, the Ministry of
Health announced a novel vaccination campaign focused on controlling
this disease.

Undersecretary Diaz explained to Radio Cooperativa the new "cocoon
vaccine" strategy, which consists in vaccinating pregnant mothers and
people older than 12 years of age whose families include newborn
infants. The reason, according to Diaz, is that "the vaccine confers
protective immunity for approximately 10 years, therefore, young
people and adults are likely to contract the disease and spread it to
infants younger than 6 months of age, who are at the greatest risk."

So far, 11 deaths have been recorded, 6 of them in the Bio-Bio Region
alone. "Children younger than 6 months of age are at risk of a very
serious disease, respiratory distress, and death," said the official.

The cocoon vaccination campaign will begin in Bio-Bio and seeks to
address the 209 per cent increase in cases of whooping cough compared
to those reported in 2010. "(Last year) to date we had 794 cases,
therefore there is an almost 3-fold increase in the numbers of
previous years (...) While the National Immunization Program
permanently vaccinates children against pertussis, this immunity is
acquired after 1 year of age, therefore during the period between
birth and the 1st year there is risk of infection," said Diaz.

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[It is not clear how many of the 2000+ cases in 2011 have occurred in
the high risk group, infants under 6 months of age. The commonest
complications of pertussis infection, especially in young infants
include apnea, pneumonia, and weight loss secondary to feeding
difficulties and post-coughing vomiting. Seizures and death also
occur. Other complications include difficulty sleeping, pneumothorax,
nose bleeds, subconjunctival hemorrhage, intracranial hematoma, rectal
prolapse, urinary incontinence, and rib fracture. The overall
complication rate of pertussis is 5-6 per cent, but among infants
younger than 6 months, the complication rate can be 3-4 times that
number.

Recommendations on the use of "cocooning" acellular pertussis vaccines
in the United States has existed in an attempt to expand protection in
susceptibles to prevent the substantial morbidity and mortality in
infants who have not been yet adequately immunized. The now
recommended use of the vaccine in pregnant women further expands these
recommendations.

The increasing susceptibility in older children and adults to
pertussis usually manifesting as chronic cough without the typical
"whoop" after appropriate primary immunization continues to be
increasingly reported. Waning immunity is generally thought to be the
cause of the problem but other issues may be at work.

>From moderator LL's comments in a prior ProMED post (Pertussis - USA:
(MN) 20100514.1573):

"Cases of pertussis in previously vaccinated older children and adults
are generally attributed to waning immunity without considering
potential differences in _Bordetella pertussis_ strains. As pointed
out in 2009 by Dr Frits Mooi (ProMED-mail Pertussis - Australia (02):
(SA) 20091108.3876): There are now many studies which show that
outbreaks of pertussis are often associated with changes in the _B.
pertussis_ population. Most recently, we have shown that more virulent
(P3) strains have appeared which we believe to be (partly) responsible
for the outbreak in the Netherlands. The P3 strains have emerged
worldwide. Any discussion on the causes of sudden upsurges in
infectious diseases should include changes in the pathogen population.
This is even true for pertussis.

Reference
---------
Mooi FR, van Loo IHM, van Gent M, et al. _Bordetella pertussis_
strains with increased toxin production associated with pertussis
resurgence. Emerg Infect Dis. 2009 Aug; 15(8): 1206-13. The full paper
is available at
http://wwwnc.cdc.gov/eid/article/15/8/08-1511_article.htm. - Mod.LL

Maps of Chile can be seen at
http://www.wwdp-natcomm.org/Images/2011/Background_Chile_Map.jpg and
http://healthmap.org/r/006H. - Sr.Tech.Ed.MJ]

See Also