Respiratory Viral Diseases 2 2024 PDF

Respiratory Viruses_2 Dr Allison Imrie Dr Megan Lloyd Learning Objectives To understand and be able to explain, the major features of the infection, disease, and public health significance of the viruses and viral diseases that are included here: Influenza viruses Coronavirus...

Respiratory Viruses_2 Dr Allison Imrie Dr Megan Lloyd Learning Objectives To understand and be able to explain, the major features of the infection, disease, and public health significance of the viruses and viral diseases that are included here: Influenza viruses Coronaviruses Hantaviruses The determinants of susceptibility to viral infection and disease  Influenza virus Influenza virus A, B and C belong to the Orthomyxoviridae family IVA and IVB commonly infect humans; IVC mostly infects animals (-)sense ssRNA viruses with segmented genomes that undergo reassortment (IVA most significantly) Transmitted by aerosols Common cause of upper and lower respiratory tract infections Disease severity associated with virus strain, pre-existing immunity induced by natural infection and vaccination; dependent on age and immune status Vaccine efficacy dependent on match between vaccine antigen and circulating virus Influenza Acute viral infection that is highly transmissible Infection is usually self limiting in healthy adults with recovery in 3-7 days Influenza can cause severe illness or death, particularly in high risk populations – very young children, pregnant women, people with chronic disease conditions or who are immunosuppressed Mortality is higher among people with complicated influenza (requiring hospitalization) and is highest in infants 65-year old were 0%, 6%, 15% and 52%, respectively Global success in containing SARS owed much to traditional public health methods of clinical case identification, contact investigation, infection control at healthcare facilities, patient isolation and community containment (quarantine) SARS emerged in late 2002. By end of global outbreak July 20023: 774 deaths Many of the affected individuals in November and December 2002 had contact with the live-game trade The number of probable cases of SARS and the date of onset of the first case in each country (or group of countries) is denoted. The countries denoted in red are those where substantial local transmission occurred https://www.nature.com/articles/nm1143 Severe Acute Respiratory Syndrome SARS Wet markets in Guangdong provided the interface for transmission to humans Specimens collected from apparently healthy animals (e.g., Himalayan palm civets (Paguma larvata) and raccoon dogs (Nyctereutes procyonoides)) found in live wild-game animal markets in Guangdong yielded a SARS-CoV-like virus with more than 99% nucleotide homology to the human SARS-CoV Proliferation of wet markets housing a range of live 'wild' animal species, such as civet cats, pictured, linked to the restaurant trade servicing the demand for exotic foods https://www.nature.com/articles/nm1143 Middle Eastern Respiratory Syndrome MERS Middle East respiratory syndrome (MERS) is a viral respiratory disease caused by Middle East respiratory syndrome coronavirus (MERS-CoV) that was first identified in Saudi Arabia in 2012 Typical MERS symptoms include fever, cough and shortness of breath. Pneumonia is common, but MERS patients may not always develop this condition. Gastrointestinal symptoms, including diarrhoea, have also been reported among MERS patients Approximately 35% of MERS cases reported to WHO have died Human-to-human transmission is possible and has occurred predominantly among close contacts and in health care settings. Outside the health care setting, there has been limited human-to-human transmission  Middle Eastern Respiratory Syndrome MERS MERS-CoV is a 𝜷 CoV Emerged Saudi Arabia 2012 A zoonotic virus - it is transmitted between animals and people Linked to human infections in dromedary camels in several Member States in the Middle East, Africa and South Asia Humans are infected through direct or indirect contact with infected dromedary camels, although the exact route of transmission remains unclear Clinical spectrum of MERS-CoV infection ranges from no symptoms (asymptomatic) or mild respiratory symptoms to severe acute respiratory disease and death Cases identified outside the Middle East are usually individuals who appear to have been infected in the Middle East and then travelled to areas outside the region Coronaviruses Is seasonal HCoV immunity protective against severe COVID-19 disease? Seasonal human coronavirus antibodies are boosted upon SARS-CoV-2 infection but are not associated with protection from severe disease https://insight.jci.org/articles/view/150449  Main clinical and laboratory findings of HFRS and HCPS HFRS=haemorrhagic fever with renal syndrome HCPS=hantavirus cardiopulmonary syndrome Summary Influenza viruses A and B are diverse viruses that are zoonotic Viral virulence is dependent on strain, host immune status and other factors Avian and swine IV infect humans at low frequency IVB-Yamagata disappeared during COVID-19 pandemic, yet to re-emerge to pre- pandemic levels Coronaviruses are a diverse group of RNA viruses that are zoonotic Seven CoV infect humans: Four HCoV are low pathogenic, cause common seasonal respiratory infections Three HCoV are highly pathogenic; SARS-CoV no longer circulates, MERS-CoV is not efficiently transmitted between humans; SARS-CoV-2 has adapted to transmit easily between people Hantaviruses cause distinct diseases that are geographically distributed An example of a zoonotic disease that emerges to infect humans when the reservoir host ecology is perturbed