Measles Morphology, Pathogenesis, Clinical symptoms, Lab diagnosis, Prevention.

 Introduction 

Measles is contagious viral infection. It is specially seen in small children but easily preventable by a vaccine (MMR). The disease spread through the air respiratory droplets produce from coughing, sneezing by the infected person. The other names for measles are morbilli or red measles.

Morphology 

1. The measle is a special envelope virus about 100-300nm in diameter.
2. It has a helical nucleocapsid, which is a coiled helix of RNA and protein.
3. It belongs to Paramyxo Viridae family and the genus morbilli virus.
4. The virus has lipid bilayer envelope drive from the host cell membrane.
5. The envelope contain 2 important surface Glycoproteins (a) Hemagglution protein (HP), (b) Fussion protein (FP).
6. HP responsible for binding to host cells receptor, FP facilitate viral entry & coli to cell fusion.
7. The RNA is enclosed within helical capsid made of nuclei protein.
8. The virus has other viral proteins such as polymerase complex protein involve in RNA transcription.
9. Matrix protein (MP) maintains the virus structure & helps in assembly.

Pathogenesis 

1. The measles morbilli virus entry the body via respiratory tract or conjunctivitis through inhalation of infection droplets. 
2. The virus initially infect alveolar macrophages and dendritic cell in the respiratory mucosa.
3. The primary receptor for the viral entry is CD150 expressed in the immune cell, such as T cell, B cell, dendritic cell and macrophages. 
4. The infection occurs within 2 to 3 exposure.

Clinical symptoms 

• Skin– red rash formation
• Respiratory – cough, pneumonia like condition.
• Conjunctiva– red watery eye.
• Gastrointestinal tract– diarrhea .
• CNS– risk of encephalitis ( inflammation of the brain).
• Lymphoid organ– sever immuno suppression.
• Rash starts on the face and spread down ward.
• Even the skin sheding can cause infection to other.

Lab diagnosis 

1. Sample collection– urine, blood serum ( for antibody detection), throat or nasopharyngeal swaps ( for RT–PCR).
2. Serological ( antibodies detection) measles specific IgM antibodies, IgM is detectable 3 to 4 days after rash onset, positive IgM is proof of measle infection. IgM can be detected by ELISA.
3. Measles specific IgG antibody in the serum, RT–PCR, throat or urine sample.
4. Immunofluorescence assay– this test detect measles antigen.

Prevention 

• Personal hygienic condition.
• Measles vaccine ( measles mumps rubella, MMR), this vaccine is anti- nuatted vaccine that provide long term protection.
• Isolate the infected individual for 3 to 4 after rash appear.
• Public awareness– information should be given to common people.