Communicable/Infectious Diseases

historical cultural perspectives (US):

• Pre-1900s: Infectious & Communicable dz’s r/t poor infrastructure, no antibiotics, or vaccines

• 2000s: chronic dzs r/t improved nutrition, sanitation, vaccines, antibiotics

• 2020: rising vaccination-preventable dz → pertussis and measles

Top 6 worldwide IDs

• pneumonia

• diarrhea

• TB

• HIV/AIDs

• Malaria

• Measles

• new emerging and old diseases

• infectious diseases = #1 cause of morbidity and mortality

Epi of CDs and IDs

• PH surveillance: monitors the who, when, what, and where

• important for disaster preparedness, agents of bioterrorism

• mandated reporting → county sheriff’s dept. → state → national (CDC)

Reportable Diseases

• HIV/AIDs

• anthrax

• botulism

• cholera

• diptheria

• chlamydia

• gonorrhea

• hepatites

• hantavirus, Hansen’s dz (leprosy)

• syphilis

• lyme dz

who’s at risk?

• confined quarters

• poverty

• world migration/immigration

• foreign country travel (less natural immunity to new area)

• risk bxs: sex, drugs

• Immunocompromised

• cultural & political issues

Endemic

disease is always present in geographical area of population

Epidemic

• disease is not always present

• flares up on occasion

• 1 case is considered epidemic after considered previously eliminated from area

• aka polio bc has been wiped from US

Pandemic

• existence of dz in large portions of population

• worldwide & affecting large pops

• HIV/AIDs is both epidemic and pandemic

Control

• reduce incidence or prevalence of disease to locally acceptable level as a result of deliberate efforts

• multi-system approach

Elimination

• remove disease from geographic area

eradication

• reduce global/worldwide incidence to zero r/t deliberate efforts, with no need for further control measures

• 100% permanent irreversible termination of dz

• smallpox

Agent Host Environmental Model

• infectious agents (virus, bacteria, toxins)

• host susceptibility (individual, population)

• environment:

  • reservoirs

  • portals of exit & entry

  • modes of transmission

Modes of Transmission

• Direct: A → B

• Indirect: A → B → C

Direct

• vertical transmission: parent → offspring (sperm, placenta, milk, vaginal fluids)

• horizontal: person → person

Indirect

• common vehicle: food, water, milk, blood, serum, saliva, or plasma

• inanimate objects

• vector-borne: ticks, mosquitos, etc.

• Airborne/Ingestion

Innate immune system

• first line of defense

• includes physical barriers: skin

• chemical barriers: enzymes, antimicrobial proteins

• immune cells

Adaptive immune system

• develops over time when exposed to pathogens

• tailored & targeted response

• T & B cells

Antigen

• molecule that triggers immune response

• protein, lipid, toxin, foreign subst.

• recognized by immune system as foreign and induces a response → antibodies

Pathogen

• infectious agent that causes disease

• micro-organisms or agent’s

• bacteria, fungi, protozoa, virus that cause illness

Inoculate

• initial, 1st exposure of pathogen (or antigen) to stimulate an antibody response

Antibodies

• blood protein produced in response to a foreign antigen

• presence = immunity

• combine chemically to defend against disease

Immunity

• presence of antibodies

• being protected against an infectious disease by producing an immune response from either having a previous infection or vaccination

Incubation Period

• time between inoculation and symptom expression (appearance of 1st sxs of disease)

Communicability/ ‘infectious period’

time during which an infectious agent may be transferred directly or indirectly from infected person to another person

Latent period

time between exposure and onset of infectiousness/communicability

Herd immunity

• level of immunity in a population

• resistance of a proportion of individual members in the group is sufficient to prevent the spread of non-immune members

• resistance of high proportion of individual members

• 80% of population

Natural immunity

• innate, species specific (antibodies)

Acquired or specific

• host acquires or develops resistance over a lifetime after previous exposure to specific agent

• having disease or getting vaccine

• + presence of antibodies

• requires competent immune system

blood titre

tests for presence of host’s antibodies

Passive Immunity

• antibody produced in another host acquired naturally by an infant from its mother or artificially by a preparation such as an anti-serum or immunoglobulin

• lasts as long as substance remains in blood stream

• ex. maternal antibodies → baby via birth

• rabies, tetanus, Hep A immune globulins as stop-gap measures when exposed

Primary Vaccine failure

• failure of vaccine to contribute any level of immunogenicity

• reasons:

  • improper care of vax

  • individual’s failure to produce antibodies

  • secondary vaccine failure: waning of immunogenicity after eliciting an initial immune response (aging)

reporting to FDA

• vaccine adverse events reporting system (VAERS)

• document batch/lot #, expiration date, and where

Vaccine Preventable Diseases birth - 6 yrs

• Hepatitis B and A

• Rotavirus

• DTap: Diptheria, tetanus, pertussis

• Haemophilus influenzae

• pneumococcoal

• poliomyelitis

• MMR: Measles, mumps, rubella

• varicella

• flu

7-18 yrs Vaccine Preventable Diseases

• flu

• Tdap (tetanus, diptheria, pertussis)

• HPV

• Meningococcal dz

• pneumococcal

TB

• 2nd leading cause of death from ID

• etiology: mycobacterium

• transmission: exposure to tubercle bacilli in airborne droplets from those with active pulmonary TB (coughing, talking, sneezing)

TB at risk

• HIV + immuno-compromised

• less stringent screening immunization nations

• poverty

• high density housing

• HC workers

• foreign born persons

TB signs

• non productive, dry cough

• fever

• hemoptysis (coughing blood)

• chest pain

• fatigue

• wt. loss

Incubation of TB

• 4-12 wks from exposure

• first 6-12 months after infection = critical period for TB onset

Latent TB (LTBI)

• may be reactivated later in life, esp. in high risk groups:

  • elderly, SUDs, malnourished, immuno-compromised

  • special concerns for HIV+/conditions that weaken immune system

• hides in lungs by forming balls of fibrous material and living immune cells with developed blood supply → granulomas

• eventually disintegrate and infectious bacilli released into airways → active dz

TB tx

• tx with meds for 3-9 months with standard meds

• Isoniazid

• Rifampin

• Rifapentine

• Purazinamide

Multi-drug resistant TB

• resistant to at least 2 first-line anti-TB drugs

• Isoniazid-INH

• Rifampin (RIF)

• if MDR > 2 drugs → less effective tx options

Direct Observed Therapy

• for active or latent TB

• ensure adherence to reduce resistance

TB PPD-Screening

• mantoux test of purified protein derivative

• place PPD: Give 0.1 ml ID (wheal)

• document: date & placement; location

• skin response read 48-72 hrs

• measure induration (hardness, not redness) in mm

> 5 mm induration is positive if

• HIV +

• +CXR

• close contact/exposure w/ infectious TB

> 10 mm is positive if:

• DM

• IDU

• Etoh

• foreign born w/ high TB rates

• medically underserved/low income residents in LTC facility, jails

• children < 4 yrs

> 15 mm induration is positive if:

• all others > age 4 yrs w/ no risk factors

Measles

• transmitted via direct contact (mouth/nasal secretions) & air

• one of world’s most contagious

Measles sxs

• high fever

• cough

• rhinorrhea

• red/watery eyes

• small white spots on inner cheeks (Koplik’s)

• rash → hands/feet

• complications: diarrhea, ear infection, PNA

• can cause infertility and deficits if left untreated

Measles at risk

• < age 5

• unvaccinated

• developing countries

• post natural disasters

• countries with war/strife

• overcrowding

Measles primary prevention

vaccination

HIV/STIs Risk Groups

• gay & bi males

• younger

• AA’s

• newborns → syphilis

Transmission of STIs

• blood

• semen

• vaginal secretions

• breast milk

clinical latency

• body shows no sxs

• final stage of symptomatic dz

HIV prevention strategies

• Harm reduction: HIV testing, condom access, sterile syringes

• STI’s screening + sex hx assessments

• 5 P’s:

  • partners

  • practies

  • protection from STI

  • past hx of STIs

  • prevention of pregnancy

Positive HIV Test

• PrEP _ linkage to care and anti-retroviral therapy

• viral suppression to < 200 copies/mL or undetectable viral lvls

Bacterial STI’s tx

antibiotics (but antibiotic resistant is emerging)

Viral STI’s

• no cure → prevention & screening/management

• HPV, HSV

• screening with pap smears, pelvic/genital exams

Bioterrorism agents

• smallpox virus

• anthrax

Smallpox

• WHO declared global eradication

• stopped routine immunizations in US in 1982

Smallpox sxs

• raised red pustular lesions face, mucous membranes, palms, feet

• 3 types: fever, malaise, N/V/D, fatigue, HA, back pain, scarring

CDC smallpox response plan

• surveillance

• case reporting

• vaccination

• response

Anthrax

• mandated reporting: DPH, State, CDC, FBI

• infected animals die, spores released from blood → air; highly resistant to disinfection + environmental destruction

Anthrax 3 clinical syndromes

• cutaneous: black lesions → low fatality if treated early

• GI: r/t undercooked meats (uncommon)

• Inhaled spores: most deadly, very rare → terrorism → occupational hazard

Anthrax sxs

• fever

• malaise

• cough

• chest pain → progresses to more severe fever, shock, death

Anthrax tx

antibiotics → Ciprofloxacin (fluoroquinolone) within 48 hrs

chemical warfare response goals:

• surveillance

• report

• isolate

• control

• eliminate/prevent

Prevention/Universal Precautions for Nosocomial Infections

• removal of devices

• environmental cleaning

• handwashing & following policies & procedures

• surveillance & education