Measles is a viral infection caused by the measles virus.
Pathophysiology
The measles virus is a part of the morbillivirus genus and the family of paramyxoviridae. It is transmitted via respiratory droplets. It infects epithelial cells of the ose and conjunctiva. It will multiply within these cells and then spread to regional lymph nodes.
Primary viraemia (spread infection into blood from the initial site of infection) occurs 2-3 days after infection. Secondary viraemia occurs days 5-7 which establishes infection in the skin and respiratory tract. This is when the prodromal phase begins. A rash develops around 2 weeks after infections. As the viraemia decreases, the rash begins to coalesce and resolve.
⚠️ Risk factors
- Lack of immunisation - with increasing anti-vaccination movements, the number of outbreaks of measles is increasing. It is highly contagious and immunisation rates of 92-95% are needed to interrupt transmission.
😷 Presentation
- Prodromal phase - occurs 10-12 days after the infection, lasting 2-4 days.
- Fever - increases to about 39ºC, then gradually decreases.
- Malaise
- Conjunctivitis
- Rhinorrhoea
- Koplik spots - these are pathognomonic (characteristic for the disease) red spots with a bluish-white central dot. They appear on the buccal mucosa. They appear 1-2 days prior to the rash appearing and disappear 1-2 days after the rash begins. They look like a grain of salt on the buccal mucosa.
- Maculopapular rash - initially presents on the face and preauricular regions. It then disseminates to the rest of the body. It fades after being present for ~5 days, usually lasting a week in total. It coalesces (fuses) then fades away.
- Lymphadenopathy
- Diarrhoea - may occur in 10% of patients.
🔍 Investigations
🥇 ELISA - for measles virus specific IgM and IgGs that are most sensitive 3-14 days after the rash presents.
🥈 PCR for detection of measles RNA 1-3 days after rash.
🧰 Management
It is important to immediately notify the local Health Protection Team.
- 🥇 Supportive management - this includes antipyretics.
- Vitamin A - in children <2 years old. This has been shown to reduce the risk of death by 87% in children <2 years old.
- Consider admission in immunocompromised, pregnant patients or children <1 years old.
🚨 Complications
Complicated measles occurs in 10-20% of patients.
- Otitis media - the most common complication.
- Pneumonia - the most common cause of death with measles
- Encephalitis - 1-2 weeks after onset. 1 in 1000 cases.
- Convulsions - 1 in 200 cases.
- Subacute sclerosing panencephalitis - 16x more common in kids who develop measles at <1 years old.
- Diarrhoea - can lead to dehydration. Especially in developing world.
- Keratoconjunctivitis - can result in blindness. It is the leading cause of childhood blindness.
- Myocarditis