Monday, April 23, 2018

PAHO Epidemiological Update: Diphtheria In The Americas


According to the noted anthropologist and researcher George Armelagos (May 22, 1936 - May 15, 2014) of Emory University - in his work The Changing Disease-Scape in the Third Epidemiological Transition-  in the mid-1970s we entered the age of newly emerging infectious diseases, re-emerging diseases and a rise in antimicrobial resistant pathogens.

While emerging pathogens - like novel flu, hemorrhagic fevers, SARS and other exotic pathogens are a major concern -  antimicrobial resistance continues to rise to alarming levels around the world, and we are seeing the resurgence of old, nearly forgotten infectious diseases like measles, mumps, scarlet fever, and diphtheria. 
Pretty much as predicted 32 years ago by Dr. Armelagos.  For a more detailed review of his work, and the reasons behind his conclusions, you may wish to revisit my 2016 blog  The Third Epidemiological Transition.
A couple of weeks ago, in UK: `Exceptional' Scarlet Fever Season Continue, we looked at the (still) unexplained return of Scarlet fever around the world. 

A month ago, in ECDC RRA On Measles In EU & Harvard Study On Mumps Vaccine, we looked at two more infectious diseases - once nearly vanquished in Europe and the United States - which are on the rise again. 

And perhaps most surprisingly, we been following the come back of diphtheria around the globe.  A few recent blogs include:
WHO Update & Risk Assessment: Diphtheria At Cox's Bazar, Bangladesh
WHO: Diphtheria Spreading Rapidly In Cox’s Bazar, Bangladesh
Vietnam MOH Warns Of Diphtheria’s Spread From Laos
Over the past 50 years diphtheria has become so well controlled by vaccines in Western countries that many doctors can now go their entire career without ever seeing a case.  
But that success story may be in danger, as over the past few years we've seen more and more outbreaks around the globe. 
Last week PAHO (the Pan American Health Organization) released an epidemiological update on Diphtheria in the Americas, citing four countries (Brazil, Colombia, Haiti & Venezuela) that have reported cases in the past year.

Hardest hit, with more than 1600 confirmed or suspected cases since 2016, has been Venezuela (see last summer's Venezuela: Reports Of A Growing Diphtheria Outbreak).

Epidemiological Update
16 April 2018

Diphtheria in the Americas - Summary of the situation
In 2017, four countries in the Region of the Americas—Brazil, the Dominican Republic, Haiti, and the Bolivarian Republic of Venezuela—reported confirmed diphtheria cases. In 2018 as of epidemiological week (EW) 14 of 2018, four countries in the Region—Brazil, Colombia, Haiti, and Venezuela—have reported suspected and confirmed diphtheria cases.
The following is a summary of the situation in each country with reported suspected and confirmed cases in 2018.
In Brazil in 2017, there were 42 suspected cases reported in 14 states. Of the reported cases, 5 were confirmed in four states: Acre (1), Minas Gerais (2), Roraima (1 fatal case, imported from Venezuela), and São Paulo (1). The remaining 37 cases were ruled out. Three of the 5 confirmed cases (2 in Minas Gerais and 1 in São Paulo) had received the full vaccination scheme. The confirmed cases range from 4 to 66 years of age (median 19 years), and four are male and one is female. Additionally, in EW 14 of 2018, 6 suspected cases were reported in 6 states; one reported in the state of Roraima (imported from Venezuela) is currently under investigation. As of EW 14, none were confirmed.
In Colombia in EW 7 of 2018, a fatal confirmed case of diphtheria imported from Venezuela was reported in La Guajira Department. The case is a 3-year-old Venezuela national with an unknown vaccination history. Onset of symptoms was on 2 January 2018 and the case died on 8 January. The case was laboratory-confirmed based on clinical, epidemiological, and laboratory criteria (Gram-positive bacilli and RT-PCR positive for Corynebacterium diphtheriae with no identification of biotype or positive toxin).
In Haiti, since the beginning of the outbreak at the end of 2014 up to EW 6 of 2018, there have been 410 probable cases of diphtheria reported, including 75 deaths. 1 Reported case-fatality rates were 22.3% in 2015, 27% in 2016 and 10.7% in 2017 and 2018. During the first four epidemiological weeks of 2018, 2 to 5 probable cases per EW were reported similar to that observed during the last four weeks of 2017.
Females accounted for 57% of the total probable cases in 2015, 50% in 2016, 60% in 2017, and 47% in 2018 (up to EW 6). With respect to vaccination coverage, between 2015 and 2018 the unvaccinated cases accounted for 17% (2018) to 38% (2015) of the total cases. Children less than 10 years of age accounted for 64% of the probable cases reported between 2017 to EW 4 of 2018.
Per the Haiti Ministry of Public Health and Population, a probable case is defined as any person, of any age, that presents laryngitis, pharyngitis or tonsillitis with false adherent membranes in the tonsils, pharynx and / or nasal pits, associated with edema of the neck.
Since the beginning of the outbreak the departments reporting the highest number of probable cases are Artibonite, Centre, and Ouest.
In Venezuela, the diphtheria outbreak that began in July 2016 remains active (Figure 1). Since the start of the outbreak until EW 10 of 2018, a total of 1,602 suspected diphtheria cases were reported (324 cases in 2016, 1,040 in 2017, and 238 in 2018), of which 976 were confirmed by laboratory (314) or epidemiological-link (662), and 142 died (17 in 2016, 103 in 2017, and 22 in 2018). The cumulative case fatality rate is 14.5%
In 2016, cases were reported in five states (Anzoátegui, Bolívar, Delta Amacuro, Monagas, and Sucre), while in 2017, 22 states and the Capital District reported confirmed cases. In 2018, 9 federal entities have reported confirmed cases. Cases have been reported among all age groups; however, the majority of cases occurred among the 1-49 year age group while the highest incidence rate occurred among the 5-19 year age group.
Health authorities are intensifying epidemiological surveillance, investigations, medical care, and vaccinations. In addition, they are maintaining continuous training of healthcare workers (based on the updated manual of standards, guidelines, and procedures for the management of the disease) as well as health education.

(Continue . . . )

Although the diphtheria vaccine is highly protective against the disease, vaccinated individuals can still can be asymptomatic carriers of toxigenic C. diphtheriae. 

And the vaccines' protection doesn't last forever, booster shots - even for adults - are required to maintain immunity (see WHO report below).
Diphtheria vaccine
Review of evidence on vaccine effectiveness and immunogenicity to assess the duration of protection ≥10 years after the last booster dose.
April 2017
So it doesn't take very long into the collapse of a nation's public health system before unvaccinated children and adults whose immunity has waned to start coming down with this highly contagious disease.
Diphtheria antitoxin (DAT) has been in short supply for several years, even in the EU (see ECDC RRA A case of diphtheria in Spain), complicating treatment.
A grim reminder of just how thin the veneer of modern civilization really is, and how easily an economic collapse, or some other major calamity (war, natural disaster, pandemic, etc.) can erode and disrupt those things we currently take for granted.

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