• enveloped (-) ssRNA
• buds from cell surface with embedded surface proteins
• attachment to cell surface glycoproteins via hemagglutinin-neuroaminidase (HN), hemaglutinin (H), or G proteins
• F protein mediated fusion
• subfamilies
  • paramyxovirinae
    • respirovirus (parainfluenza)
    • rubulavirus (parainfluenza, mumps)
    • morbillivuris (measles)
    • henipavirus
  • pneumovirinae
    • pneumovirus (resp. syncytial virus)
    • metapneumovirus)

• types- 7 viruses (1,2,3,4A,4B)
• type 3 the most common (4A, B are rare)
• ssRNA virus
• attach to cells via HN protein
• fusion via F protein
• immunity is incomplete
• by age 5, most kids have had types 1, 2, 3

• acute infection of URT/LRT
• causes 30-50% of cases of otitis media
• characteristic illness
  • croup (larygeotracheobronchitis)
    • usually caused by type 1
    • symptoms- barking cough, hoarse voice, stridor (subglottic narrowing)
    • steeple sign on X ray- sign of subglottic narrowing
  • bronchiolitis- inflammation of lower airways
    • leading cause of bronchiectasis
      • saccular enlargement of distal airways with wall thickening
      • destruction and increased mucus production
  • more severe disease (pneumonia) in immunosuppressed hosts

• ssRNA virus
• attach to sialic acid via HN protein
• endemic throughout world, but controlled via MMR
• recent outbreak in US related to importation
• humans are only host
• transmitted by direct contact, droplets, fomites

• incubation period: 2-4 weeks
• prodromal low grade fever, malaise, headache
• within 24 hrs, earache and tenderness with parotid palpitation
• bilateral parotid enlargement over 2-3 days
  • unilateral in 25%, other salivary glands as well in 10%
• resolution in 3-10 days
• post pubertal epididymo-orchitis in 25%
• meningitis and encephalitis RARE

Vaccine preventable

genetics/char/structure/epi of measles

• ssRNA (Morbillivirus)
• attaches via hemagglutin protein
  • CD46 (complement regulatory protein)
  • SLAM/CD150 (signaling lymphocyte attachment molecule)
• epidemiology
  • predominantly in childhood
  • humans only hosts
  • worldwide
  • mainly in winter/spring
  • US cases related to importation
• highly contagious, droplet spread by infected nasopharyngeal secretions

measles pathogenesis

• infects epithelial cells of resp. tract
• spread by viremia to RE system, then secondary viremia
• replicates in conjunctiva, resp. tract, GI, GU, lymphatic system, bv's, CNS
• multinucleated giant cells in skin, mucosa
• disease caused by T cell response to virus infected cells lining the capillaries

Measles clinical characteristics/manifestations/ complications

• mucosal enanthem called Koplik's spots
• maculopapular rash starts 14-18 days after infection
  • initially on face and spread over 3-4 days to involve trunk and limbs
  • can be extensive and confluent (fade in 72 hrs)
• complications
  • pneumonia
  • bacterial superinfection
  • encephalitis
  • subacute sclerosing panencephalitis (SSPE)

Vaccine preventable

genetics/char/structure/epi of RSV

• ssRNA
• attach via G protein
• epidemiology
  • major cause of LRT infection in young children
  • primarily in winter, spring
  • outbreaks last up to 20 wks
  • all children infected in first few yrs of lif
• major groups are A and B with subtypes in each group (both groups may circulate during epidemic)

RSV pathogenesis

• incubation period 2-8 days
• inoculation in nose, eye
• bronchiolitis (lymphocytic peribronchiole infiltration)
  • endothelial sloughing, mucus secretion
  • bronchiole obstruction with impendance to air flow, hyperinflation, and bronchiectasis
• pneumonia char. by mononuclear cell infiltration

Clinical complications/tx/prevention of RSV

• complications
  • acute- apnea, increase risk of infant aspiration
  • chronic- recurrent wheezing, bronchiectasis
  • immunocompromised- pneumonia
• tx
  • aerosolized ribavarin
  • bronchodilators, corticosteroids
• prevention
  • strict infection control
  • for high risk, monthly RSV Ig IV or palivizumab (monoclonal Ab bind to F protein)

genetics/char/structure/epi of metapneumovirus

• ssRNA virus
• attach to G protein (similar structure to RSV)
• two major groups are A and B with subtypes in each group
• epidemiology
  • infect all age groups
  • most children infected by age 5
  • mainly winter months

clinical characteristics/complications of metapneumovirus

• URI's, bronchiolitis, pneumonia
• may be coinfection with RSV or influenza

Henipa virus characteristics

• zoonotic
• attach to cell surface via G proteins

clinical characteristics/epi of Hendra

• IDed in Australia
• transmission: bat to horse or rarely horse to people
• distrubtion follows that of fruit bat
• illness caused
  • pneumonia
  • encephalitis

Epi/clinical characteristics of Nipah virus

• epidemiology
  • ID in Malaysia, Singapore
  • natural reservoir is fruit bat
    • deforestation brought them closer to affected hosts
    • transportation of pigs spread the disease
  • kills pigs, dogs, humans
• clinical complications
  • widespread vasculitis, esp. in CNS
  • cause 40% fatality

characteristics/genetics/structure of influenza

• enveloped ssRNA virus
  • 8 different segments
  • allows for genetic reassortment when more than one virus infects a single cell
• types A, B, C
  • significant difference in structure, genetics, organization, host range, epi, clinical char.
• covered with surface projections or spikes: HA and N
  • used to subtype influenza A virus

influenza pathogenesis

• enters resp. tract via small particle aerosols produced by talking, coughing, sneezing
• typically, infection limited to superficial cell of URT and LRT
• penetrates columnar epithelial cell leading to cell death
  • inhibits protein synthesis
  • induced apoptosis
• loss of ciliated and mucus secreting epithelial cells reduces clearance of bacteria (could lead to super infection)

clinical characteristics/complications of influenza

• incubation 1-2 days
• abrupt onset of illness
• fever, rigors, myalgias, hadache
• followed by sore throat, dry cough, nasal obstruction/discharge
• may progress to viral pneumonia
• secondary bacterial infections not uncommon
• may be followed by Guillian Barre syndrome

influenza dx

• nasopharyngeal swab
• rapid Ag test
  • distinguish influenza A and B
  • 40-80% sensitivity
• PCR (distinguish subtypes)
• viral isolation

influenza tx

• M2 inhibitors
  • amantadine (oral)
  • rimantadine (oral)
• neuroaminidase inhibitors (typical)
  • oseltamivir (oral)
  • zanamivir (inhaled)

impact of oseltamavir

• great reduction in influenza in long term care facilities
• effective in household px
• effective community px
• some efficacy in reduction in hospitalizations
• 32 hrs faster resolution of symptoms

types of vaccines used against influenza

• trivalent influenza vaccine
  • intramuscular
  • give to anyone greater than 6 mnths old
• live attenuated influenza vaccine
  • intranasal
  • only be given ages 5-49

target groups for TIV vaccination

• children ages 6-23 months
• women who will be pregnant during flu season
• persons over age of 65
• children and adolescents on long term aspirin therapy
• adults and children with chronic medical conditions
• residents in long term care facilities
• household contacts who have frequent contact with persons at hirh risk and who can transmit influenza to those persons at high risk
• health care workers

antigenic drift

• minor shift in HA or NA with only minor changes in antigenicity

epidemic

• seasonal outbreaks caused by subtypes of influenza virus or related viruses that already circulate among the community

reassortment

• recombination of genomic material in a cell co infected with 2 different viruses

antigenic shift

• major shifts in HA and/or NA (no antigenic relationship between old strain and new strain)

define pandemic

• global oubreaks that occur when new influenza A virus appears or emerges in human population
  • cause serious illness, and then spreads easily from person to person worldwide

How do pandemics arise

• wild water fowl are natural reservoirs of influenza and can spread the virus to domestic birds
• avian influenza virus evolve into new strains capable of infecting humans
  • all human influenza viruses arise from avian viruses
• a new avian derived flu virus that can reproduce and spread in humans may lead to a pandemic

Whats needed for a pandemic strain

• novel virus (little or no immunity)
• capable of causing disease in humans
• highly pathogenic
• capable of sustained person to person transmission

H5N1 influenza epidemiology

• highly pathogenic and spreading from Asia and across Europe and Africa
• bird to human transmission with close contact
• human to human transmission rare
• high mortality

Origin of H1N1

• originated via reassortment of swine
• first cases associated with swine contact in Mexico
• represents a quadruple reassortment btw swine from Europe and Asia, avian and human strains