Microbio: Module 7 - Viral Diseases

Acute Infection

Sudden onset of symptoms; comes and goes; relatively short duration; results in burst of virions released from infected cells

Chronic Infection

Continuous production of low levels of viral particles and virus can be transmitted in absence of symptoms

Latent Infection

Genome remains silent in host cells and can reactivate to cause productive infection

Fecal-Oral Transmission

Viruses may have more than one route of entry and mode of transmission which makes them difficult to categorize and there may be little connection between the route of entry and the particular organs/tissues involved with the disease

How do viral diseases differ from bacterial diseases in terms of mode of transmission, how the disease is categorized, and route of entry?

Often diagnosed according to their clinical symptoms, specifically by lab diagnosis which is the only way to definitively diagnose a particular viral infection; yes

How are viral infections most frequently diagnosed? Does this type of diagnosis give a definitive causative agent?

Enveloped viruses are generally easier to eliminate with standard disinfectants and soaps since their outer membrane is fragile and easily disrupted by naked viruses have a rigid protein shell that makes them highly resistant to environmental stress, drying, and many common cleaners

Explain the significance of a virus having an envelope vs. being naked in terms of how difficult they are to eliminate.

Fecal-oral route and raw/undercooked shellfish from contaminated waters

Food and Waterborne Viral Diseases: Mode of Transmission for Gastroenteritis

2-10 days

Food and Waterborne Viral Diseases: Incubation Period for Gastroenteritis

Norovirus, Rotavirus, Enteroviruses

Food and Waterborne Viral Diseases: Causative Agent(s) for Gastroenteritis

None

Food and Waterborne Viral Diseases: Reservoir for Gastroenteritis

RotaTeq and Rotarix vaccines available against rotavirus infections since 2010

Food and Waterborne Viral Diseases: Treatment/Vaccines for Gastroenteritis

19 to 21 million norovirus infections per year and children younger than 5 and older adults particularly vulnerable

Food and Waterborne Viral Diseases: Statistics for Gastroenteritis

Fecal-oral route

Food and Waterborne Viral Diseases: Mode of Transmission for Hepatitis A

30 days to 2 months

Food and Waterborne Viral Diseases: Incubation Period for Hepatitis A

Hepatitis A virus

Food and Waterborne Viral Diseases: Causative Agent(s) for Hepatitis A

Humans

Food and Waterborne Viral Diseases: Reservoir for Hepatitis A

None

Food and Waterborne Viral Diseases: Treatment/Vaccines for Hepatitis A/E

2,007 new cases in 2016, cases have been increasing yearly since 2012

Food and Waterborne Viral Diseases: Statistics for Hepatitis A

Fecal-oral route, contaminated drinking water in developing countries, consumption of uncooked/undercooked pork, dry deer meat, raw shellfish

Food and Waterborne Viral Diseases: Mode of Transmission for Hepatitis E

Hepatitis E - Inflammation of liver

Food and Waterborne Viral Diseases: Causative Agent(s) for Hepatitis E

Varies depending on the specific genotype of the virus

Food and Waterborne Viral Diseases: Reservoir for Hepatitis E

Uncommon in US, endemic in Asia, Middle East, African, and Central America

Food and Waterborne Viral Diseases: Statistics for Hepatitis E

No vaccines

Food and Waterborne Viral Diseases: Treatment/Vaccines for Hepatitis E

Direct fecal-oral contact, indirect contact with saliva or fecal matter, or by contaminated sewage/water

Food and Waterborne Viral Diseases: Mode of Transmission for Poliomyelitis

7-14 days

Food and Waterborne Viral Diseases: Incubation Period for Poliomyelitis

Poliovirus

Food and Waterborne Viral Diseases: Causative Agent(s) for Poliomyelitis

Humans

Food and Waterborne Viral Diseases: Reservoir for Poliomyelitis

Salk (killed/inactivated) and Sabin (oral, live attenuated)

Food and Waterborne Viral Diseases: Treatment/Vaccines for Poliomyelitis

Last case in US was in 1979 and it is still endemic in some regions of Middle East, recently eradicated in Africa

Food and Waterborne Viral Diseases: Statistics for Poliomyelitis

Jaundice

A medical condition characterized by a yellowing of the skin, the whites of the eyes, and mucous membrane; happens from damage to liver

Gastroenteritis, Hepatitis A/E, and Poliomyelitis

What are the food and waterborne viral diseases?

Common cold, RSV, Influenza, COVID-19, Measles, Mumps, German Measles, Chickenpox/Shingles, and Small pox

What are the respiratory viral diseases?

Respiratory droplets, by hands or fomites (doorknobs, faucets, furniture, toys, etc.)

Respiratory Viral Diseases: Mode of Transmission for Common Cold

1-3 days

Respiratory Viral Diseases: Incubation Period or Common Cold

Large variety of distinctive group of viruses, each group can have over 100 strains; includes: Coronavirus, Enterovirus, Rhinovirus, Adenovirus, and HMPV

Respiratory Viral Diseases: Causative Agent(s) for Common Cold

Humans and fomites

Respiratory Viral Diseases: Reservoir for Common Cold

Over the counter medications to help with symptom relief and no vaccine

Respiratory Viral Diseases: Treatment/Vaccines for Common Cold

Millions of cases in the US each year and adults have an average of 2-3 colds/year, children have more

Respiratory Viral Diseases: Statistics for Common Cold

Respiratory droplets and by hands or fomites

Respiratory Viral Diseases: Mode of Transmission for RSV or Respiratory Syncytial Virus

4-5 days

Respiratory Viral Diseases: Incubation Period for RSV or Respiratory Syncytial Virus

Respiratory Syncytial Virus

Respiratory Viral Diseases: Causative Agent(s) for RSV or Respiratory Syncytial Virus

Humans and fomites

Respiratory Viral Diseases: Reservoir for RSV or Respiratory Syncytial Virus

Supportive care, incubation with mechanical ventilation in some cases, vaccines are available for older adults, pregnant woman, or monoclonal antibody products are available to protect infants and young children

Respiratory Viral Diseases: Treatment/Vaccines for RSV or Respiratory Syncytial Virus

Most widespread cause in infants under 6 months of age, by age 2 most are infected, for children younger than 5 there are 2.1 million outpatient visits/year and 57,527 hospitalizations

Respiratory Viral Diseases: Statistics for RSV or Respiratory Syncytial Virus

Respiratory droplets and aerosols and fomites play a secondary role

Respiratory Viral Diseases: Mode of Transmission for Influenza A,B,C

24-48 hours

Respiratory Viral Diseases: Incubation Period for Influenza A,B,C

Influenza

Respiratory Viral Diseases: Causative Agent(s) for Influenza A,B,C

Humans (especially young children) and animals (waterfowl and pigs)

Respiratory Viral Diseases: Reservoir for Influenza A,B,C

Supportive care, bed rest, fluids, annual flu vaccine, antivirals: relenza, tamiflu, rapivab

Respiratory Viral Diseases: Treatment/Vaccines for Influenza A,B,C

Hemagglutinin (H)

As many as 500 spikes, attaches to sialic acid receptor on host epithelial cells that line respiratory mucosa, and aid viral penetration into cells

Neuraminidase

100 on surface of each virus and plays a role in release of new virions

Both serve as virulence factors and both are antigens

What do neuraminidase and hemaglutinin both have?

RSV

Which respiratory virus is particularly life threatening to children under 6 months of age?

Common cold

Which respiratory disease yields the highest number of cases per year?

Reservoir is from humans, wild aquatic birds, domestic poultry, and swine and they have the ability to cause an epidemic AND pandemics

Influenza A: What are the reservoirs and does it have the ability to cause epidemics or pandemics?

It is the primary reason it remains an ongoing pandemic threat and it has a major, abrupt antigenic change in the H or N spikes and it results from different viral strains mixing and creating this strain

Why is it important that Influenza A has animal reservoirs?

Reservoir is primarily humans (rarely seals) and it can cause an epidemic

Influenza B: What are the reservoirs and does it have the ability to cause epidemics or pandemics?

Humans (and occasionally pigs/dogs) and they do not cause epidemics or pandemics

Influenza C: What are the reservoirs and does it have the ability to cause epidemics or pandemics?

About 200,000 hospitalizations; 3,000 & 49,000 deaths; and 31.4 million get infected

Cite at least three statistics related to the impact of influenza.

Comes down to symptom onset and severity; colds develop gradually with mild symptoms whereas flu strikes suddenly and causes high fever, extreme fatigue, and severe body aches

Describe how you could differentiate whether a patient had a cold vs. the flu.

Aerosol and droplet transmission

Respiratory Viral Diseases: Mode of Transmission for COVID-19 or SARS COV-2

2-14 days

Respiratory Viral Diseases: Incubation Period for COVID-19 or SARS COV-2

COVID 19

Respiratory Viral Diseases: Causative Agent(s) for COVID-19 or SARS COV-2

Still unknown, bats suspected and suspicion of intermediate host like snakes

Respiratory Viral Diseases: Reservoir for COVID-19 or SARS COV-2

Multiple vaccines available and antivirals (paxlovid, remdesivir)

Respiratory Viral Diseases: Treatment/Vaccines for COVID-19 or SARS COV-2

According to CDC - 103,957,053 total cases and 1,123,613 deaths in the US

Respiratory Viral Diseases: Statistics for COVID-19 or SARS COV-2

Respiratory droplets

Respiratory Viral Diseases: Mode of Transmission for Measles or Rubeola Virus

10-21 days

Respiratory Viral Diseases: Incubation Period for Measles or Rubeola Virus

Measles

Respiratory Viral Diseases: Causative Agent(s) for Measles or Rubeola Virus

Humans

Respiratory Viral Diseases: Reservoir for Measles or Rubeola Virus

MMR vaccine

Respiratory Viral Diseases: Treatment/Vaccines for Measles or Rubeola Virus

2,030 confirmed measles cases in US 2026

Respiratory Viral Diseases: Statistics for Measles or Rubeola Virus

Respiratory droplets

Respiratory Viral Diseases: Mode of Transmission for Mumps

10-20 days

Respiratory Viral Diseases: Incubation Period for Mumps

Mumps

Respiratory Viral Diseases: Causative Agent(s) for Mumps

Humans

Respiratory Viral Diseases: Reservoir for Mumps

MMR vaccine

Respiratory Viral Diseases: Treatment/Vaccines for Mumps

2009-2010 two large outbreaks in NYC and Guam multiple outbreaks from 2015-2017

Respiratory Viral Diseases: Statistics for Mumps

Respiratory droplets, urine, and prenatal transmission

Respiratory Viral Diseases: Mode of Transmission for Rubella or German Measles

12-32 days

Respiratory Viral Diseases: Incubation Period for Rubella or German Measles

German Measles

Respiratory Viral Diseases: Causative Agent(s) for Rubella or German Measles

Humans

Respiratory Viral Diseases: Reservoir for Rubella or German Measles

MMR Vaccine

Respiratory Viral Diseases: Treatment/Vaccines for Rubella or German Measles

Less than 10 cases in US each year

Respiratory Viral Diseases: Statistics for Rubella or German Measles

Respiratory droplets, contact with fluid from blisters, mother to child via placenta

Respiratory Viral Diseases: Mode of Transmission for Chickenpox/Shingles or Varicella Zoster Virus

10-23 days

Respiratory Viral Diseases: Incubation Period for Chickenpox/Shingles or Varicella Zoster Virus

Chickenpox and shingles

Respiratory Viral Diseases: Causative Agent(s) for Chickenpox/Shingles or Varicella Zoster Virus

Humans

Respiratory Viral Diseases: Reservoir for Chickenpox/Shingles or Varicella Zoster Virus

Chickenpox vaccines (MMRV)

Respiratory Viral Diseases: Treatment/Vaccines for Chickenpox/Shingles or Varicella Zoster Virus

More than 3.5 million cases; 9,000 hospitalizations; 100 deaths prevented by chickenpox vaccine each year

Respiratory Viral Diseases: Statistics for Chickenpox/Shingles or Varicella Zoster Virus

Person to person via saliva droplets, contaminated clothing and bedding

Respiratory Viral Diseases: Mode of Transmission for Smallpox or Variola Virus

7-19 days

Respiratory Viral Diseases: Incubation Period for Smallpox or Variola Virus

Smallpox

Respiratory Viral Diseases: Causative Agent(s) for Smallpox or Variola Virus

Humans

Respiratory Viral Diseases: Reservoir for Smallpox or Variola Virus

TPOXX - Developed in 2018 to treat smallpox in case of bioterrorism event

Respiratory Viral Diseases: Treatment/Vaccines for Smallpox or Variola Virus

Killed 500 million people in the 20th century and disease eradicated in 1979

Respiratory Viral Diseases: Statistics for Smallpox or Variola Virus

Crowded indoor environment, low humidity, poor ventilation, and frequent close personal contact

What are some of the conditions that aid in the spread of influenza?

Antivirals are highly time-sensitive, they must be started within 1 or 2 days of initial symptoms; the virus is genetically volatile and prone to rapid mutation; and specific antivirals in medications are not recommended for complication or progressive illnesses, hospitalized patients, or young children without careful evaluation

Describe some of the limitations associated with the antivirals used to treat influenza.

To treat or prevent secondary bacterial infections

Why would a physician prescribe antibiotics to an elderly patient infected with influenza even though antibiotics are only effective at treating bacterial infections?