Emerging infectious diseases

Plasmid encoding _______ is being transferred among the Enterobacteriaceae family- these bacteria are gram (-) rods

**THIS CARD REQUIRES REVIEW**carbapenum resistance

Influence of animal food production on EID due to mass rearing of animals

-crowded pens favors transmission -spillover into handlers -antibiotics in animal feed increase selection pressure for resistant organisms -food travels the world- increased risk for dissemination

TB reemergence coincided with ______ epidemic and ______ with antimicrobial therapy, an important factor favoring selection of resistant strains. This can result in __________ and _________ TB

1. HIV/AIDS 2. noncompliance 3. Multi-drug resistant (MDR) 4. Extremely drug resistant (XDR)

What infectious agents are most likely to emerge? Give reasoning as well.

1. RNA viruses due to high mutation rate, ability to form quasi-species, and reassortment of segmented genome 2. bacteria that can acquire genes via horizontal gene transfer due to acquisition of virulence factors such as antibiotic resistance, toxins, adhesins, etc. 3. Pathogens with broad host range due to the ease of developing ability to infect new hosts

In order to adapt to a new host, viruses can use many mechanisms: 1. evolve the ability to bind ________ in a new host 2. use _______ in the new host 3. acquire the ability to bind _________ of a new host (this may not be sufficient to allow a virus to infect, however, because the virus may require _______ to adapt)

1. a new receptor 2. a homolog of an existing receptor 3. target cells; viral polymerase or transcription factors

In SARS, the virus developed the ability to ________, and once this occurred it was unable to infect bat cells; in MERS the virus binds to __________, and is therefore still able to infect bats in addition to humans.

1. a new receptor (angiotensin converting enzyme 2, ACE2) 2. a homologous receptor (dipeptidyl peptidase 4)

stages involved in adapting to human hosts to becoming a pandemic: 1. pathogen is transmitted among ______ 2. ________ transmission is initiated with limited __________ transmission 3. develops sustained _______ transmission

1. animals 2. animal to human; human to human 3. human to human

MRSA summary review

1. antibiotic resistance is common in S. aureus 2. MRSA was initially HA, but CA strains are emerging 3. mecA encodes PBP2a, located on SCCmec (types I-III= HA, types IV and sometimes V and VII = CA) 4. HA and CA have different virulence properties determined by the type of SCC plasmid they have

Common animal reservoirs include (5)

1. bats 2. rodents 3. birds 4. swine 5. non-human primates

Chikungunya virus summary

1. clinical features are similar to dengue 2. adapted to 2° vector 3. mostly in Central/South America

Influence of economic development on EID

1. deforestation increases contact between animal reservoirs and humans, and limits the range of natural predators for rodents and insect vectors 2. urbanization increases person to person contact and therefore transmission (in addition to the effects of poor hygiene, malnutrition, limited health care access) 3. moving to the suburbs increases exposure to tick vectors (Lyme)

Nipah virus in 1998 caused ______ in Malaysia- caused by transfer from ______ to pigs due to deforestation of natural habitat, exposure of pigs to feces, and subsequent transfer to _____

1. encephalitis 2. bats 3. handlers

What types of changes can occur in an emerging pathogen to increase its emergence in a population?

1. expansion of geographic range 2. changing virulence 3. changing host range

E. coli 0104:H4 outbreak in May-June 2011 was facilitated by a __________. The outbreak strain has two properties from two different types of E. coli, which are:

1. food-borne outbreak from contaminated sprouts 2. STEC (expresses Shiga toxin associated with dysentery) and EAggEC (Enteroaggregative E. coli which attaches via aggregative adherence fimbriae) -it is thought that EAggEC strain acquired the STEC via bacteriophage *additional virulence factor: antibiotic resistance plasmid CTX-M-15

Factors influencing emergence in a new geographic area

1. international trade or travel 2. migrating birds 3. climate change (natural disasters, expansion of animal reservoirs/vector range)

Emerging infectious disease is an infectious disease whose incidence is increasing due to ______, or ______

1. its first introduction to a new host population 2. in an existing population as a result of long-term changes in its underlying epidemiology

Influence of food production on EID (4)

1. mass rearing of animals 2. open markets 3. contamination of food 4. mass distribution of contaminated food

Factors that influence emergence of infectious disease

1. microbial adaptation 2. economic development, agricultural practices 3. climate/weather 4. international trade/commerce

What are the three classifications of EID?

1. newly emerging (not recognized in humans or newly recognized) 2. Reemerging (existed in past but demonstrates increase in incidence, possibly involving a new host or geographic range) 3. Deliberately emerging (bioterrorism)

Dengue summary

1. primary vector is Aedes aegypti in tropical/subtropical areas, adapted to indoors and outdoors 2. secondary vector Aedes albopictus is more common outdoors and adapted to cooler temps (increase range) 3. Not many cases in US because limited contact sustained, low housing density, and use of air conditioning and screens

What is important in order to limit the emergence of infectious diseases?

1. surveillance/detection 2. containment 3. identification- how it causes disease, spreads, is treated, and prevented 4. development of treatments on a large scale

Most common EIDs

1. zoonoses (transferred from animal to human host) 2. vector borne (mosquitos/ticks etc that transmit from an animal reservoir to a human host, often the 'dead-end')

What factors influence sustained human to human transition (stage 3)?

Air travel international trade movement of reservoir host or vector -all allow global spread and spread to naïve hosts

Surveillance can be mediated by the ______ or ______. _____ was established to disseminate information on EID and outbreaks via the internet.

CDC WHO ProMed

What factors influence the transition from stage 1 (animal-animal transmission, pre-emergence) to stage 2 (localized emergence, animal-human transmission)?

Ecological, social, socioeconomic changes -overlapping habitats, expanded transmission among an established host, migration, introduction into a different (non-human) host

Example of a pathogen emerging in a new geographic area that may just be newly detected

Hantavirus -outbreak of acute respiratory illness on Navaho Indian reservation caused by mouse vector, but the virus had been present in US for many years previously

Example of a pathogen introduced to a new geographic area

West Nile -unexplained cases in NYC with simultaneous bird fatalities at Bronx Zoo -easily disseminated because it was never seen in US before, population was therefore susceptible, and the mosquito vector was already in place

In prions, the normally folded prion protein undergoes _______ into a pathogenic form

a conformational change *also triggers other prion proteins to undergo the same change

What is the importance of the role of expansion of mosquito vectors in EID?

able to spread to multiple host species (variation) periodic epidemics multiple vector species increased contact with human hosts

SARS and MERS are ______ that recently acquired the ability to infect humans- both are related to bat transmission, with SARS possibly evolving in _______ and MERS still under investigation (suspicions point to _______)

coronaviruses cats (civets) camels

Factors that have influence the Ebola outbreak

demographic and environmental changes -population of continent has tripled -deforestation -increased travel

How is Hanta virus an example of a virus spreading to a new geographic area?

drought in the early 1990s was followed by an unusually wet 1993, which increased food for mice and thus the number of mice that harbored the virus- increased exposure to humans increased the transmission to people

The emergence of yellow fever, dengue, and chikungunya is a story of _________ driving vector adaptation, which in turn has driven ___________

human behavior viral adaptation

In avian influenzas H5N1 and H7N9, the adaptation for human-to-human transmission requires _______

increased affinity for a-2,6-linked sialic acid

In general, a virus that binds to a new receptor in a new host loses its ability to ________

infect the previous host (usually animal reservoir)

Categories of EIDs (3)

pathogen infects a new host pathogen develops novel traits within the same host pathogen extends its range into a new geographic area

Bacterial pathogens often have clusters of genes encoding virulence factors known as ______, which can be transferred horizontally via _________

pathogenicity islands or virulence cassettes plasmids or bacteriophages

Mad Cow Disease (variant Creutzfeldt-Jakob disease) is transmitted by ________ via ingestion of contaminated bovine meat

prions

In addition, identification of _________ has enabled more effective use of antibiotics, and the assessment of the organisms' _______ has helped identify the common source and animal reservoir in order to track the route of transmission

resistance relatedness

Surveillance of Enterovirus D68: it is a _____ illness more common in _______, severe in individuals with ______. Currently the CDC has developed ________ which enhances our ability to track the outbreak

respiratory children asthma a new faster lab test

E. coli 0104:H4 has been ________ in order to develop a specific _______, determine the source of the pathogen, and garner information on ______ and ______ of the pathogen

sequenced diagnostic test origin virulence

In the the 2009 H1N1 pandemic, the virus is more easily transmitted among humans than seasonal flu because:

the virus reassorted in swine, pre-adapted to readily infect humans