Measles virus vs SARS-CoV-2

Reading various articles about Measles virus and Covid-19 virus i.e. SARS-CoV-2, various similarities can be seen. The key point is not only its internal structure but its outer envelope, especially the entry points that attach to human cells.

 I have tried to summarize the comparison here:

 Measles Virus
  1. Image: It bears striking similarities in envelope and shape to SARS-CoV-2 image. Further images can be seen at  CDC website.
  2. Structure: It  is a single-stranded, negative-sense, enveloped, non-segmented RNA virus of the genus Morbillivirus within the family Paramyxoviridae (or (-)ssRNA virus).
  3. Envelope: The measles virus has two envelope glycoproteins, responsible for host cell binding and invasion, on the viral surface – hemagglutinin (H) and membrane fusion protein (F).  Three receptors in the human cells, for the H protein are:
      • complement regulatory molecule CD46, 
      • the signaling lymphocyte activation molecule (SLAM or  CD150) and 
      • the cell adhesion molecule Nectin-4
  4. Replication: The negative sense strand of ssRNA (single stranded RNA) is used to create a positive copy, then this used to create a new negative copy, and so on, to create many copies of the ssRNA. 
  5. Size: Its size is 100 to 300 nm. It seems to be bigger than SARS-CoV-2.
  6. Stability:  It is inactivated after 30 minutes at 56°C. However, when freeze-dried with a protein stabilizer, can survive storage for decades at -70°C. It can be inactived by both acids (pH less than 5) and alkalis (pH greater than 10), many disinfectants, including 1% sodium hypochlorite, 70% alcohol and formalin.
  7. Light: Virus can be destroyed by visible and UV light. 
  8. Complications: Rash appears within a few weeks. But main worry is immunosuppression caused by infection that can lead to secondary bacterial and viral infections resulting in life-threatening pneumonia. Following rash the respiratory epithelium is infected basolaterally via a second receptor, nectin 4.
  9. Antibodies: Both IgM and IgG antibodies are produced during the primary immune response and measles-specific IgM can be detected in the serum as early as the first day of rash. After the rubella virus infects the nasopharynx, it multiplies in the lining of the respiratory tract and in local lymph nodes before passing into the bloodstream.

 SARS-CoV-2 virus

  1. Image: It shows striking similarities to Measles virus, especially the envelope.
  2. Structure: It  is a single-stranded, positive-sense, enveloped, single linear RNA segment virus (or (+)ssRNA virus). It belongs to the broad family of viruses known as coronaviruses.
  3. Envelope: The measles virus has three envelope glycoproteins, responsible for host cell binding and invasion, on the viral surface – spike (S), envelope (E) and membrane protein (M).  The spike protein used the receptor angiotensin converting enzyme 2 (ACE2) on human cells to to enter cell. Also it has lipid bilayer on top to protect the virus.
  4. Replication: Initial spike protein priming by transmembrane protease, serine 2 (TMPRSS2) is essential for entry of SARS-CoV-2. After that RNA is released into host  cell forcing it to replicate.
  5. Size: Its size is 50 to 200 nm. 
  6. Stability: The virus may remain viable on plastic and steel for up to three days, but does not survive on cardboard for more than one day or on copper for more than four hours It can be inactived by both acids (pH less than 5) , many disinfectants, including 1% sodium hypochlorite and 70% alcohol. It can last inside refrigerator for a month.
  7. Light: Virus can be destroyed by UV light. 
  8. Complications:Symptoms are influenza-like and include fever, headache, diarrhoea, and shivering. Cough (initially dry), shortness of breath are present in the first and/or second week of illness. Severe cases often evolve rapidly, progressing to respiratory distress and requiring intensive care.
  9. Antibodies: Both IgM and IgG antibodies are produced during the primary immune response. CR3022 is the antibody produced by immune system which binds to the  spike protein. After the corona virus infects the nasopharynx, it multiplies in the lining of the respiratory tract.  
  10. Vaccine: This antibody CR3022  exists for SARS disease also.So if vaccines exist for SARS already then it can be used against Covid-19 disease too.

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