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Questions and Answers
What is the primary transmission method for influenza viruses?
Influenza viruses are primarily transmitted by aerosols.
What factors influence the severity of influenza illness in individuals?
Severity is influenced by virus strain, pre-existing immunity from natural infection or vaccination, age, and immune status.
Why are babies and elderly individuals at higher risk of severe influenza?
They have weaker immune systems, making them more susceptible to severe illness from influenza.
What role did public health methods play in containing SARS?
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How does the efficacy of an influenza vaccine depend on circulating viruses?
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What are the three types of influenza viruses identified in humans?
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What was the total number of deaths by the end of the SARS outbreak in July 2003?
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What is the typical recovery time for healthy adults infected with influenza?
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What is the primary interface for the transmission of SARS to humans in Guangdong?
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What animal species were found to carry a virus closely related to human SARS-CoV?
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When and where was MERS first identified?
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What are some typical symptoms of MERS?
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What percentage of reported MERS cases have resulted in death?
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What type of transmission can occur with MERS, and in which contexts?
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How is the demand for exotic foods linked to the proliferation of wet markets?
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What is the nucleotide homology percentage between the SARS-CoV-like virus found in animals and the human SARS-CoV?
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What is the primary mode of transmission for MERS-CoV?
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In what year and country did MERS-CoV first emerge?
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What is the clinical spectrum of MERS-CoV infection?
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How do seasonal human coronaviruses relate to immunity against severe COVID-19?
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What contributes to the diversity of influenza viruses A and B?
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Which two hantavirus syndromes are mentioned, and what are they associated with?
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What impact did the COVID-19 pandemic have on the circulation of Influenza B Yamagata?
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What differentiates the highly pathogenic coronaviruses from low pathogenic ones?
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Study Notes
Influenza Viruses
- Influenza viruses A, B, and C belong to the Orthomyxoviridae family
- IVA and IVB commonly infect humans while IVC mostly infects animals
- Influenza viruses are (-)sense ssRNA viruses with segmented genomes that undergo reassortment, especially IVA
- Transmitted through aerosols
- Common cause of upper and lower respiratory tract infections
- Disease severity depends on the virus strain, pre-existing immunity from natural infection or vaccination, age, and immune status
- Vaccine efficacy depends on the match between the vaccine antigen and circulating virus
Influenza Infection
- Acute viral infection, highly transmissible
- Usually self-limiting in healthy adults with recovery in 3-7 days
- Can cause severe illness or death, especially in high-risk populations like very young children, pregnant women, people with chronic diseases, or immunosuppressed individuals
- Mortality is higher among those with complicated influenza requiring hospitalization and is highest in infants (52%)
- Mortality rates for 65-year olds are significantly lower (0%)
SARS Emergence
- SARS emerged in late 2002, with the global outbreak ending in July 2003
- 774 deaths were recorded during the outbreak
- Many affected individuals in November and December 2002 had contact with the live-game trade
- Significant local transmission occurred in various countries
SARS Transmission
- Wet markets in Guangdong, China, provided the interface for transmission to humans
- Specimens from apparently healthy animals like Himalayan palm civets and raccoon dogs in these markets yielded a SARS-CoV-like virus with over 99% nucleotide homology to the human SARS-CoV
- Wet markets housing various live 'wild' animal species, like civet cats, linked to the restaurant trade catering to the demand for exotic foods, are believed to have played a significant role in the transmission
MERS
- Middle East respiratory syndrome (MERS) is a viral respiratory disease caused by Middle East respiratory syndrome coronavirus (MERS-CoV), first identified in Saudi Arabia in 2012
- Typical MERS symptoms include fever, cough, and shortness of breath, with pneumonia being common
- Gastrointestinal symptoms, like diarrhea, have also been reported
- Roughly 35% of MERS cases reported to the WHO have resulted in death
- Human-to-human transmission is possible, primarily occurring among close contacts and in healthcare settings, with limited transmission outside these settings
MERS-CoV
- A 𝜷 CoV
- Emerged in Saudi Arabia in 2012
- A zoonotic virus, transmitted between animals and humans
- Linked to human infections in dromedary camels in several Middle Eastern, African, and South Asian countries
- Humans are infected through direct or indirect contact with infected dromedary camels, but the exact route of transmission remains unclear
- The clinical spectrum of MERS-CoV infection ranges from asymptomatic or mild respiratory symptoms to severe acute respiratory disease and death
- Cases identified outside the Middle East typically involve individuals infected in the Middle East who traveled to other regions
Coronaviruses
- A diverse group of RNA viruses that are zoonotic
- Seven CoV infect humans
- Four HCoV are low pathogenic and cause common seasonal respiratory infections
- Three HCoV are highly pathogenic: SARS-CoV no longer circulates, MERS-CoV is not efficiently transmitted between humans, and SARS-CoV-2 has adapted to transmit easily between people
Hantaviruses
- Cause distinct diseases with geographical distribution
- An example of a zoonotic disease that emerges to infect humans when the reservoir host ecology is perturbed
Seasonal HCoV Immunity and Severe COVID-19
- Seasonal human coronavirus antibodies are boosted upon SARS-CoV-2 infection, but aren't associated with protection from severe COVID-19 disease
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Description
This quiz explores the characteristics and impact of influenza viruses A, B, and C, including their transmission, disease severity, and effects on different populations. It also covers the role of vaccines and immune response. Test your knowledge about this significant infectious disease.
