Measles natural history, complications and prognosis
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Guillermo Rodriguez Nava, M.D. [2]; Vidit Bhargava, M.B.B.S [3]
Overview
Measles spreads through the air by breathing, coughing or sneezing. It is so contagious that any child who is exposed to it and is not immune will probably get the disease. The virus lives in the mucus in the nose and throat of the infected person. When that person sneezes or coughs, droplets spray into the air. The virus can live on infected surfaces for up to 2 hours and spreads so easily that people who are not immune will probably get it when they come close to someone who is infected. Measles is a disease of humans.
Complications with measles are relatively common, ranging from relatively mild and less serious diarrhea, to pneumonia and encephalitis (subacute sclerosing panencephalitis - SSPE). Complications are usually more severe amongst adults who catch the virus.
Measles itself is unpleasant, but the complications are dangerous. Six to 20 percent of the people who get the disease will get an ear infection, diarrhea, or even pneumonia. One out of 1000 people with measles will develop inflammation of the brain, and about one out of 1000 will die.
Natural History
- The incubation period usually lasts 10 days (with a range from 7 to 18 days) from exposure to the onset of fever.
- The disease is characterised by prodromal fever, conjunctivitis, coryza, cough and the presence of Koplik spots (reddish spots with a white centre) on the buccal mucosa.
- A characteristic red rash appears on the third to seventh day beginning on the face, becoming generalized and lasting 4-7 days.
- The rash is caused by an allergic response due to the union of sensitized lymphoid cells and measles antibody with the virus in the skin.
- A similar reaction occurs in the epithelium, leading to conjunctivitis, stomatitis, pneumonitis and acute inflammation of the gastrointestinal tract.
- This allergic reaction clears the virus and is followed by a period of anergy during which many immune responses are greatly diminished.
- This immuno-suppression, which may last for many weeks, results in increased susceptibility to other infections such as those caused by pneumococcus.
- The three major causes contributing to the high case-fatality rate are pneumonia, diarrhea and croup.[1]
Complications
Complications with measles are relatively common. In industrialized countries, complications occur in around 10-15% of cases, ranging from relatively mild and less serious diarrhea, to pneumonia and encephalitis (subacute sclerosing panencephalitis - SSPE). The frequency of complications in developing countries is less well known. At least three-quarters of cases in developing countries can be expected to have at least one complication and some have multiple systems involvement. Complications are usually more severe amongst adults who catch the virus. SSPE is a very rare, but fatal degenerative disease of the central nervous system that results from a measles virus infection acquired earlier in life. The first signs of SSPE may be changes in personality, a gradual onset of mental deterioration and myoclonia (muscle spasms or jerks). The diagnosis of SSPE is based on signs and symptoms and on test results, such as typical changes observed in electroencephalographs, an elevated anti-measles antibody (IgG) in the serum and cerebrospinal fluid, and typical histologic findings in brain biopsy tissue. There are reports of remission and some treatments are available; however, the average survival is one to two years. There is no evidence that measles vaccine can cause SSPE.
The fatality rate from measles for otherwise healthy people in developed countries is low: approximately 1 death per thousand cases. In underdeveloped nations with high rates of malnutrition and poor healthcare, fatality rates of 10 percent are common. In immunocompromised patients, the fatality rate is approximately 30 percent.
Serious Complications[2]
- Diarrhea
- Ear infections
- Pneumonia
- Encephalitis
- Seizures
- Death
Approximately 20% of reported measles cases experience one or more complications. These complications are more common among children under 5 years of age and adults over 20 years old. Measles causes ear infections in nearly one out of every 10 children who get it. As many as one out of 20 children with measles gets pneumonia, and about one child in every 1,000 who get measles will develop encephalitis. (This is an inflammation of the brain that can lead to convulsions, and can leave your child deaf or mentally retarded.) For every 1,000 children who get measles, one or two will die from it. Measles can also make a pregnant woman have a miscarriage, give birth prematurely, or have a low-birth-weight baby. In developing countries, where malnutrition and vitamin A deficiency are prevalent, measles has been known to kill as many as one out of four people. It is the leading cause of blindness among African children. Measles kills almost 1 million children in the world each year.
Measles can also lead to life-long disabilities, including blindness, brain damage and deafness. Low vitamin A status has been associated with a higher rate of complications and a higher death rate, as it has similar pathological effects on epithelia and the immune system.
Prognosis
Measles itself is unpleasant, but the complications are dangerous. Six to 20 percent of the people who get the disease will get an ear infection, diarrhea, or even pneumonia. One out of 1000 people with measles will develop inflammation of the brain, and about one out of 1000 will die.
Most measles deaths (98%) occur in developing countries, where vitamin A deficiency is common. The case fatality rates in developing countries are normally estimated to be 3-5%, but may reach 10-30% in some situations. This compares with 0.1% in many industrialised countries. Through synergy with measles infection, vitamin A deficiency contributes to the estimated 1 million childhood deaths from measles every year. Half of the childhood corneal blindness in developing countries is attributable to vitamin A deficiency, and half to measles infection.[1]