CORONA VIRUS
Influenza virus (Orthomyxoviruses) p507-8 AnantNarayan
Ability to cause epidemics and pandemics : The reason the virus is able to cause epidemics and pandemics lies in its ability to undergo antigenic variation.
Antigenic drift, resulting from mutation and selection, is responsible for the epidemics. It has been shown experimentally that passaging the virus in the presence of antiserum leads to the appearance of such mutants.
Ability to cause epidemics and pandemics : The reason the virus is able to cause epidemics and pandemics lies in its ability to undergo antigenic variation.
Antigenic drift, resulting from mutation and selection, is responsible for the epidemics. It has been shown experimentally that passaging the virus in the presence of antiserum leads to the appearance of such mutants.
Pandemics are caused by a virus strain that has undergone antigenic shift. The variation in such instances is so marked and involves different polypeptides simultaneously that mutation cannot explain it.
It is now held that pandemic strains originate from some animal or avian reservoir, either spreading to humans directly by host range mutation, or as a result of recombination between human and non-human strains .
Hybrids can be produced by growing human and non-human strains together in eggs. Recombinants can also be obtained from experimental animals exposed to mixed infection.
It has been shown by genetic studies that both the 1957 Asian virus and the 1968 Hong Kong virus were such recombinant hybrids.
Chemoprophylaxis has been reported to be successful with the antiviral drugs amantadine and rimantadine which block the viral M2 protein which functions as an ion channel. These act only with the type A virus and not with the type B, which lacks the M2 components .Zanamivir and oseltamivir, new drugs designed to block viral neuraminidase, have been found effective in the treatment and prevention of influenza, when administered as a nasal spray.
=====================
It has been shown by genetic studies that both the 1957 Asian virus and the 1968 Hong Kong virus were such recombinant hybrids.
Chemoprophylaxis has been reported to be successful with the antiviral drugs amantadine and rimantadine which block the viral M2 protein which functions as an ion channel. These act only with the type A virus and not with the type B, which lacks the M2 components .Zanamivir and oseltamivir, new drugs designed to block viral neuraminidase, have been found effective in the treatment and prevention of influenza, when administered as a nasal spray.
=====================
p572 anantnarayan
CORONA VIRUSES
CORONA VIRUSES
A group of spherical or pleomorphic enveloped RNA viruses, carrying petal- or club-shaped peplomers on their surface has been classified as coronaviruses. The name refers to the fringe of surface projections surrounding the virus, resembling the solar corona.
There are two groups: acid-labile viruses (associated with common cold-like illnesses) and acidstable viruses (associated with human and animal gastroenteritis).
There are many serotypes, which are mostly fastidious and difficult to grow in cell culture systems.
Coronavirus types
❖ Human coronavirus 229E.
❖ Human coronavirus OC43.
❖ SARS-CoV.
❖ Human coronavirus NL63 (HCoV-NL63, New Haven coronavirus).
❖ Human coronavirus Hl<Ul.
❖ Middle East respiratory syndrome coronavirus (MERSCoV),previously known as Novel coronavirus 2012 and HCoV-EMC.
Human coronaviruses were first isolated from cases of common cold by inoculating organ cultures of human embryonic trachea with nasopharyngeal washings. Inhibition of ciliary motility indicates virus growth. Inoculation in human volunteers induces common cold after an incubation period of 2-5 days. The resulting immunity is poor and re-infections can occur even with the same serotype. They appear to be the second most common cause of the common cold, particularly in winter, next only to rhinoviruses.
Severe acute respiratory syndrome (SARS):
In November 2002, Guangdong province in South China experienced an outbreak of an unusual respiratory infection, with many deaths. The world outside knew about it only in February 2003, when a physician from Guangdong visited Hong Kong, fell ill and died there, after infecting 12 persons who had stayed in the same hotel. They, in turn, went to their countries to fall ill and initiate outbreaks there. By July, when the pandemic was controlled, it had affected over 30 countries, with many thousands of cases and over 800 deaths. India escaped the SARS epidemic; however, a few suspect cases were detected and quarantined.
The coronavirus responsible for SARS appears to be a new virus distinct from other coronaviruses, which had been classified into three types: mammalian viruses in types 1 and 2 and avian viruses in type 3. The new SARS virus is coronavirus type 4. The fact that it is a new virus is indicated by the absence of an antibody to it in human and animal sera collected from previous years. It may be a recombinant of some animal and human viruses. The virus has been isolated from Chinese wild civets and raccoon dogs, but not from pigs, dogs, cattle or poultry.
Spread: SARS spreads by inhalation of the virus present in droplets or aerosols of respiratory secretions of patients. Fecal aerosols also may be infectious. The incubation period is under 10 days. The disease starts as a fever with cough or other respiratory symptoms.Diarrhea is sometimes seen. The chest radiograph shows pneumonic changes. Death is due to respiratory failure.
There are two groups: acid-labile viruses (associated with common cold-like illnesses) and acidstable viruses (associated with human and animal gastroenteritis).
There are many serotypes, which are mostly fastidious and difficult to grow in cell culture systems.
Coronavirus types
❖ Human coronavirus 229E.
❖ Human coronavirus OC43.
❖ SARS-CoV.
❖ Human coronavirus NL63 (HCoV-NL63, New Haven coronavirus).
❖ Human coronavirus Hl<Ul.
❖ Middle East respiratory syndrome coronavirus (MERSCoV),previously known as Novel coronavirus 2012 and HCoV-EMC.
Human coronaviruses were first isolated from cases of common cold by inoculating organ cultures of human embryonic trachea with nasopharyngeal washings. Inhibition of ciliary motility indicates virus growth. Inoculation in human volunteers induces common cold after an incubation period of 2-5 days. The resulting immunity is poor and re-infections can occur even with the same serotype. They appear to be the second most common cause of the common cold, particularly in winter, next only to rhinoviruses.
Severe acute respiratory syndrome (SARS):
In November 2002, Guangdong province in South China experienced an outbreak of an unusual respiratory infection, with many deaths. The world outside knew about it only in February 2003, when a physician from Guangdong visited Hong Kong, fell ill and died there, after infecting 12 persons who had stayed in the same hotel. They, in turn, went to their countries to fall ill and initiate outbreaks there. By July, when the pandemic was controlled, it had affected over 30 countries, with many thousands of cases and over 800 deaths. India escaped the SARS epidemic; however, a few suspect cases were detected and quarantined.
The coronavirus responsible for SARS appears to be a new virus distinct from other coronaviruses, which had been classified into three types: mammalian viruses in types 1 and 2 and avian viruses in type 3. The new SARS virus is coronavirus type 4. The fact that it is a new virus is indicated by the absence of an antibody to it in human and animal sera collected from previous years. It may be a recombinant of some animal and human viruses. The virus has been isolated from Chinese wild civets and raccoon dogs, but not from pigs, dogs, cattle or poultry.
Spread: SARS spreads by inhalation of the virus present in droplets or aerosols of respiratory secretions of patients. Fecal aerosols also may be infectious. The incubation period is under 10 days. The disease starts as a fever with cough or other respiratory symptoms.Diarrhea is sometimes seen. The chest radiograph shows pneumonic changes. Death is due to respiratory failure.
MERS-CoV:
Middle East Respiratory Syndrome (MERS) is a viral respiratory illness that has recently been reported. It was first detected in Saudi Arabia in 2012. The virus that causes MERS is called Middle East Respiratory Syndrome Coronavirus (MERSCoV). Coronaviruses are common viruses that infect
most people at least some time in their lives. Human coronaviruses usually cause mild to moderate upperrespiratory tract illnesses. However, MERS-CoV is different from any other coronavirus previously found in people. This virus is thought to have come from animals including camels. Infection spreads though respiratory secretions.
most people at least some time in their lives. Human coronaviruses usually cause mild to moderate upperrespiratory tract illnesses. However, MERS-CoV is different from any other coronavirus previously found in people. This virus is thought to have come from animals including camels. Infection spreads though respiratory secretions.
Symptoms: Persons infected with MERS-CoV develop severe respiratory illness. They have fever, cough and shortness of breath. Severe cases may have acute renal failure.
Treatment: Currently there is no vaccine to prevent the infection. Strict isolation and barrier nursing is the only way to prevent spread.
novel COVID 19 info: General Public Info
novel COVID 19 info: General Public Info
Subscribe to:
Posts (Atom)