Acute and Persistent infection

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Pathogenesis of Acute vial infection

Features:

rapid on set

high vireamia

short and severe

immune clearance

Infection timeline

Incubation period: it takes time for the symptoms to occur and if there are any they are generic and non-specifc to a type of viral infection

- these can be long or short

long usually means the site of entry is not near the site of infection

short incubation means symptoms appear only at the primary site

Infectious period: symptoms are displayed

vireamia is at its peak and the adaptive immune response has ben induced

Viral clearance: full adaptive immune response and memory cells are created

Types of viruses that cause acute infections

influenza

poliovirus

norovirus

west nile virus

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Influenza Virus

Three types

A - responsible for pandemics/ cause of serious illness

B - cause of serious illness

C

Transmission

Direct contact/contact with contaminated surfaces

droplets

Pathogenesis

initial the virus invades muscoal surface

In humans, entry is gained through α(2,6) sialic acid on the epithelial cells (in birds α(2,3) sialic acid)

Continues to spread down the resporatory tract

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Features

1-5 day incubation period

high fever within 24 hr

between days 2 and 3 the fever drops

effects differ in the elderly, immunocompramised and children

occur during colder months due to more crowding in spaces

Pandemic Potential

lack of avian receptor in URT

the re-assorting of avians viruses with human one can lead to more efficient transmission by making hybrid viruses

Complications

Viral pnuemonia

secondary bacterial infection

reye syndrome

Treatment

oseltamivir

zanamavir

vaccine

non-drug therapies

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Norovirus

Features

ssRNA+

cause of 40% of gastroenteritis

1-10 viral particles needed

Transmission

fecal-oral

enclosed settings lead to rapid spread (hospitals)

Pathogenesis

binds to carbohydrates in gut lumen

transcytosis of viral particles leads it to infection DC, Mφ and B cells

infects and damages the vili in the jejunum

presentation of both viral and bacterial antigens effects the antiviral immune responses

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Epidemiological Features

incubation 12-28 hr

can be infectious for up to two weeks

no long term immunity

rehydration therapy and pain management for treatment

Pathogenesis of Persistent Viral Infection

General Background

long term and parallel host's life

initially start as an acute infection