Chikungunya Fever

Chikungunya Fever

IntroductionViral disease;Mosquito-borne:Aedes aegypti and Aedes albopictus;

Incubation period of 4-7 days;

Rarely fatal;

Arthralgia may persist for months, or even years;Can become cause ou Chronic pain and disability.Symptoms:High fever 40 C;Joint pain and swelling;Rash;Headache;Muscle pain;Nausea;Fatigue.

WHO, 2014; PAHO, 2014

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TransmissionInfected mosquito bites;Become infected when feed on na infected person, or other hosts (mokeys, rodents, birds);

Thiberville et al., 2013; CDC, 2014; PAHO, 2014

Figure 1: Mosquitoes of the Aedes gender.Source: Centers for Disease Control and Prevention, 2014Available at: http://www.cdc.gov/chikungunya/pdfs/CHIKV_FACTSHEET_CDC_Generalpublic(09-17-2014).pdf

Figure 2: Life-cycle of Chikungunya virus in Africa.Source: Thiboutot et al., 2010.

Attack rate Is a measure of morbidity, it is defined as the proportion of those who became ill after being exposed to a certain risk.E.g.: In na outbreak of gastroenteritis with 50 cases, among a population at risk of 2500 people, the attack rate will be:50/2500 = 0.2 or 2/100 or 2%

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Aedes mosquitos have shown a large geographical expansionRisk for the establishment of the disease

A. aegypti was considered the primary vector until 2006;A. albopictus: Ranked as the most invasive species of mosquito in the world;Capable of adapting to the peridomestic environment.

It is found in places where the A. aegypti is rare and where it is prevalent;

According to Medlock et al. (2012), A. albopictus presents a major threat to public health in Europe.

Medlock et al., 2012; Tomasello and Schlagenhauf, 2013; Thiberville et al., 2013

EpidemiologyOriginal endemic areas: Africa, Asia and Indian subcontinent;

Outbreaks showed to be unpredictable:Intervals of 7-20 years between individual epidemicsIntervals of 4-5 decades between major epidemics

2004: Virus caused massive outbreaks in Asia and Africa:More than 2 million infections;Attack rates reaching 68% in some areas.Mid 2005: Island of La RunionAttack rate: 34%; Mortality rate: 0.1%Virus spread to the Seychelles, Mauritius, Maldives and other Indian Ocean islands;

Thiberville et al., 2013; CDC, 2014; PAHO, 2014

It is believed that the imune system plays a central role in the periodicity of the disease, because of a long lasting imune protection that is acquired after the infection.This in reinforced by the fact that recurrent outbreaks preferentially target the youngest age-groups. (Thiberville et al., 2013 apud Robert et al., 1996).5

2007: First reports of the disease in Europe:Index Case: Man returning from India;Outbreak in North-eastern Italy;Attack rate: 5.4%; Mortality rate: 0.5%;Molecular analysis:E1-226V mutation;Presence of Aedes albopictus.

2010: Cases of Chikungunya in France:Index Case: Girl coming from India;Three weeks later: Two other girls got sick.

2013: First cases of authoctonous transmission in the Americas:Caribbean.

PAHO (7 November, 2014)39 countries874,103 suspected cases and 16,669 laboratory confirmed cases

Tomasello and Schlagenhauf, 2013

Two girls, one was a neighbor of the Index Case, and invited the other (classmate) to spend the night both reported being bitten several times by mosquitoes. The mutation was not present.6

Country/TerritoryAuthoctonous transmission casesImported cases (Confirmed)Incidence rate (per 100,000 pop)DeathsPopulation (millions)Death rate (per thousand)SuspectConfirmedCanada080025.1820.0United States of America111,83900320.0510.0Dominican Republic498,916844,796.2610.4040.09Brazil173370.10200.3620.0America914,96015,9062,23696.5150964.3410.16

Table 1: Reported cases of Chikungunya Fever in the Americas, 21 November 2014.Source: Pan American Health Organization, 2014Available from: file:///C:/Users/RCorassa/Downloads/2014-nov-21-cha-chikungunya-cases-ew-47.pdf

Figure 3: Countries and territories with reported cases of Chikungunya, 2014CDC, 2014

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Figure 4: Diagram for the determinants of Chikungunya disease.Arunachalam et al., 2009

ConclusionChikungunya disease is expanding throuout the world;

The spread of the disease depends on the distribution of its vectors;

The vectors are expanding geographicalyThe disease is related to lower socioeconomic status (disadvantadged populations), poor sanitation and agglomerations;

The disease is rarely fatal, but can impose a heavy burden on the health systems.Setbon and Raude, 2008; FIOCRUZ, 2012

Vector EcologyClimate:Abundant rain;High temperatures;Availability of breeding sites:Deposits of stagnant water;Feeding opportunities;Vector capacity.Virus strain;3 diferent strains;E1-226V mutation;Facilitate the transmission through A. albopictus.

Source: http://www.thehindu.com/news/cities/chennai/181-cases-of-dengue-reported-this-year/article3559831.eceArunachalam et al., 2009; Tomasello and Schlagenhauf, 2013Virus biology

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Social and ecological contextPopulation/SocietalPopulation density: Agglomerations facilitate the spread of the disease;Urbanization: Urbanized areas may offer less breeding sites for the vectors;Sanitation;Education;Migration: Introduction of infected hosts in non-endemic areas;

Individual/Family Household:Housing condition;Water storage;

Community:Type and abundance of public spaces/Land use: Empty lots may offer breeding sites for the vectorsArunachalam et al., 2009, FIOCRUZ, 2012

Vector controlLegislation:Water distribution and storage;Vector control policies;Waste disposal;Control services:Surveillance programs;Type, coverage and quality of control services;Human resources/efficiency/sustainability;Costs;Stakeholders:Arunachalam et al., 2009

ReferencesPAHO, 2014 - http://www.paho.org/hq/index.php?option=com_content&view=article&id=8303&Itemid=40023&lang=enCDC, 2014 (Map) - http://www.cdc.gov/chikungunya/pdfs/ChikungunyaWorld%20Map_11-04-2014.pdfWHO, 2014 (Fact sheet) - http://www.cdc.gov/chikungunya/pdfs/ChikungunyaWorld%20Map_11-04-2014.pdfMedlock et al., 2012 - A Review of the Invasive Mosquitoes in Europe: Ecology, Public Health Risks, and Control OptionsThiboutot et al., 2010. Chikungunya: A potentially emerging epidemic?WHO, 2014. Epidemiological alert Chikungunya and Dengue fever in the AmericasTomasello D., Schlagenhauf P. Chikungunya and Dengue autocthonous cases in Europe, 2007-2012. Travel Medicine and Infectious Diseases, v. 11, pp. 274-284, 2013.

FIOCRUZ, 2012 - http://www.fiocruz.br/rededengue/cgi/cgilua.exe/sys/start.htm?infoid=134&sid=3

Arunachlam et al., 2009 - Eco-bio-social determinants of dengue vector breeding: amulticountry study in urban and periurban Asia http://www.who.int/bulletin/volumes/88/3/09-067892/en/

Setbon M., Raude J. Chikungunya on Reunion Island: Social, Environmental and Behaviourial factors in na epidemic contexto. 2008