Objectives
- Overview of viruses causing the respiratory infecitons in humans
- reasons for the prevalence of respiratory viruses in human populationa nd emrgence of new respiratory diseaes
- influenza viruses
- Corona viruses
- Relationship between the infection with RSV and development of asthma
Most symptoms of respiratory disease is inflammation
URT
- runny nose, sneezing
- congestion due to eexcess mucus production
- dry or wet cough LRT
- Chest cold, wheezing, pneumonia
- ARDS
Human respiratory Viruses
- adenoviruses
- corona viruses
- orthomyxoviruses
- paramyxoviruses
- picornaviruses
- parvovirus
Why respiratory viruses so prevalent
Alternative winter seasons in northern and southern hemisphere allow respiratory viruses to stay in population
RNA genome is prone to mutations which is what most respiratory viruses have.
As they change so much vaccines and antivirals need to constantly developed
Adenoviruses
DNA genome in additioni to common cold can cause GI URI and eye infecitons in human beings. can cause ARDS in young military recruits immunisations exist
Coronaviruses
cause 15-30% of common colds, no vaccine availible
Novel Coronaviruses - SARS 2 causues COVID-19
main killer was the cytokine storm
Anti-COVID 19 drug
- Paxlovid - Effectibe in reducing viral load
- REGEN-COV - neutralise viral profeny
- Remdesivir - nucleoside analogue
- Hydroxycholoroquine - antimalarial - no evidence of efficacy
- Dexamathasone - reduced inflammation
- Baricitinib - reduces inflammation
- Tocilizumab - reduced inflammation
Orthomyxoviruses
INfluenza
4 types a infects humans mammals and birds b and c infect humans d infects cattle and pigs a and b cause seansoal epidemics type a has cause 4 pandemics
INfluenza A
rnagenome, segmentes hemagluttin and neuraminidase are major antigens
redular zoonotic transmittion
they are further subtypes by HA and NA
antigenic shift, change the antigens surrounding the
avian influenza
Anti flu drugs
symmetrel - inhibites merging tmaiflu inhibits progeny xofluza 0 inhibits RNA polymaerase`
Paramyxoviruses
Common in infant and young children Examples:
- Parainfluenza virus
- Respiratory syncytial virus
- Human metapneumovirus
- Mumps virus
- Measles virus A vaccine is available
RSV
Major couse of LRTIs in infants symptoms range from common cold, Bronchitis, pneumonia Bronchitis is distinctly associated with RSV and it increases risk of asthma and wheezing RSV can increase risk along 3 factors
- oversensetisation of the innate immune response to allergens
- abnormalities in lung de3velopment and function
- overexpression of nerve growth factors leading to airway hyperactivity Major cause of otitis media in infects
2 major antigenic types a and b 2 vaccine for adults 60/over no children vaccine passive immunation supporting vare
Picornaviruses
Rhinovirsues
aggrevate asthma main cause of common cold in humans
Coxsackie viruse
rna genome groups a and b no vaccine causes herpangina, pumps and sores in mouth and foot and mouth disease
Parvovirus
Genetic recombination
2 cells infecting same cell and switch componenets or DNA