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Hull York Medical School
Dr Kirstine Eastick
Transmission and treatment of viral infections
Viral infections are very varied and have many different effects
Variety in the structures of virus – including single and double stranded, envelope
viruses etc.
What makes a virus different?
Bacteria are opportunistic while viruses are specific to certain cells which is why
there is a huge variety, and they are not opportunistic
Cells usually happily welcome viruses because they’ve been tricked into thinking
these are wanted by the cell
Viruses are obligate parasites
Most common types of viruses are respiratory viruses which are transmitted through
aerosol or droplet methods – this also applies to rash viruses
Saliva is also a method of transmission – kissing, cuddling (children and adolescents)
Contact viruses – mucosal (herpes, HIV)
Usually, the skin is a good barrier due to its defences which usually kill viruses and
bacteria which should not be there but those which can get through these defences
are viruses such as HPV
Ingestion (norovirus, rotavirus) – enteric transmission
Percutaneous transmission such as blood-borne viruses (HIV/Hepatitis B and C) or
arboviruses (malaria)
Mother to child transmission – connected by placenta – viruses can travel through
this
Congenital infection (Rubella, Parovirus B19)
Perinatal contracted after due to mothers bleeding
Zoonoses – caught through ingestion (meat and excretion which can release viruses
into the air) includes Hepatitis E and Lassa Virus - bites (Rabies) – insects can cause
Zika, Dengue virus (mosquitoes) but also ticks can transmit viruses such as tick-borne
encephalitis
Problems of intervention
Replicated by subverting host cell metabolism – while it’s simple with bacteria as
they have their own metabolism this is not the case with viruses
Difficult to intervene due to possibility of damaging the host due to this
Viruses vary in their metabolism which makes it even harder – hard to find a pan
viral anti-viral agent
Does mean that if you get it right you can get very specific antivirals which can be
useful
Prevention
Physical prevention – PPE, condoms
Passive – passing on antibodies
Active – vaccination – stimulating immunity before they are exposed to the virus –
can use killed viruses, engineered antigens or live attenuated vaccines (this is what
the smallpox vaccine was done)
Viral replication
Need to interfere with the replication of a virus to cure it
Protease an important target as is the release stage
Antiviral classes
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