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Japanese Encephalitis (JE)
Definition:
Japanese encephalitis is a disease that is spread to humans by infected mosquitoes in Asia. Japanese encephalitis is a seasonal disease that usually occurs in the temperate regions of China, Japan, and Korea from April to October. In other places, disease patterns vary with rainy seasons and irrigation practices. It is caused by the Japanese encephalitis virus that has a complex life cycle involving domestic pigs as the host and a specific type of mosquito (Culex tritaeniorhynchus) as the disease vector. Up to 1 in 50 people who are infected by a mosquito bite will develop an illness.
Who is at risk?
- Residents of rural areas in endemic locations;
- Active duty military deployed to endemic areas;
- Travelers who visit rural areas.
Symptoms:
- Symptoms usually appear 6-8 days after the bite of an infected mosquito.
- Most infected people develop mild symptoms of fever with headache or no symptoms at all.
- In people who develop a more severe disease, Japanese encephalitis usually starts as a flu-like illness, with fever, chills, tiredness, headache, neck stiffness, tremors, nausea, and vomiting.
- Confusion and agitation can also occur in the early stages. The illness can progress to a serious infection of the brain (encephalitis) and can be fatal in 30% of cases.
- Amongst the survivors, another 30% may have serous brain damage, including paralysis.
Treatment:
- There is no specific treatment for Japanese encephalitis.
- Antibiotics are not effective against viruses, and no effective anti-viral drugs for this condition have been discovered.
- Care of patients centers on treatment of symptoms and complications.
Prevention:
- Know the epidemics: Countries which have had major epidemics in the past, but which have controlled the disease primarily by vaccination, include China, Korea, Japan, Taiwan and Thailand. Countries that still have periodic epidemics include Vietnam, Cambodia, Myanmar, India, Nepal, and Malaysia.
- Minimize outdoor activities at the cooler hours of dusk and dawn as these specific mosquitoes mainly feed in open space at these hours.
- Travelers should wear light color clothing with long sleeves, use mosquito repellent on exposed skin, stay in air-conditioned or well-screened rooms and use a bed net and aerosol insecticides.
- Vaccination: Japanese B vaccination is available in Hong Kong. The recommended schedule is to use 2 doses with 10 days apart. The recent recommended schedule that suggests better efficacy is 3 doses on day 1, day 7 and day 28.
- A Japanese encephalitis vaccine should be offered to people spending a month or longer in endemic areas during the trans-mission season, especially if the journey includes rural areas. Vaccinations should also be considered for people spending < 30 days in endemic areas and people whose activities, such as extensive hiking in rural areas, place them at high risk for exposure.
- Rates of serious allergic reactions to the vaccines such as generalized urticaria or angioedema are low.
- Japanese encephalitis acquired during pregnancy has potential for intrauterine infection and fetal death. These specific factors should be considered when advising elderly people and pregnant women who plan visits to areas where Japanese encephalitis is endemic.
(Neonatal) Jaundice
Definition:
Jaundice comes from a French word meaning yellow and 'neonatal' refers to the period before the baby is a month old. Jaundice happens when bilirubin, a yellow pigment, accumulates in our blood and becomes visible on the skin or in the eyes as a yellow tinge. Normally bilirubin comes from the break down of haemoglobin in aged blood cells, which is excreted by the liver. Bilirubin can accumulate when there is much unwanted haemoglobin, or when the liver is unable to handle the waste.
The foetus needs to extract oxygen and nutrients from the mother, hence foetal blood is highly concentrated. When a baby is born, the excess haemoglobin may exceed the capacity of the relatively immature liver. Bilirubin thus accumulates in the blood and tissue, and the skin and eyes become visibly yellow. This is called 'physiological jaundice'. It typically appears on day 3 to day 4, peaks by day 5 to day 7 and disappears by 10 days to 2 weeks.
Who is at risk?
When bilirubin levels reach very high levels, the yellow pigment can enter brain cells and cause permanent brain damage and deafness. This is unusual for normal babies with no other risk factors, but is common in the past in babies whose blood grouping is 'incompatible' with that of the mother, as in mothers with Rhesus negative blood groups having Rhesus positive babies. Fortunately this has become rare in modern obstetric care.
Blood group 'O' Mothers carrying babies with blood groups A, B or AB may also produce a small amount of antibodies that can break down newborns' red cells, resulting in early jaundice. Usually the antibodies are not as high and jaundice not as severe as with Rhesus incompatibility. Locally, babies with G6PD deficiency (Glucose-6-phosphate dehydrogenase deficiency, also called Favism) is another common cause of neonatal jaundice. Babies born through a difficult labour with severe bruises are also at risk.
Premature babies, babies with a low birth weight, and sick babies requiring special care are also more prone to the harmful effect of bilirubin, as the bilirubin would find its way into brain cells more readily in such circumstances.
Symptoms:
A severely jaundiced baby may be irritable, restless, sluggish at feeding, or may even develop fits. But most jaundiced babies do not have other symptoms apart from looking yellow. Jaundice usually first appears in the face and whites of the eyes and then moves to the chest, abdomen, arms, and legs as the bilirubin level increases. One needs to have a good light source, preferably daylight or under fluorescent lights, to detect a mild degree of jaundice. Beware of colour reflected from clothing and home decorations.
Treatment:
Colour perception can be subjective. To assess the severity and follow progress, nurses and doctors often rely on equipment that tests the skin or blood before decisions on treatment are made. Different instruments and different units of measurement can cause confusion. Other factors to consider are the age, body weight, maturity of the baby and the presence of other risk factors. Pediatricians may vary slightly in their recommendations based on individual circumstances.
When jaundice appears early, when bilirubin level is very high, or is likely to rise quickly, doctors may recommend phototherapy--light treatment. Fluorescent lights of a particular wavelength can change the bilirubin to a water-soluble chemical, which is more effectively excreted. Usually one or two days' treatment is enough to bring down the bilirubin to safe levels, but occasionally can take longer. The baby's eyes need to be covered and the clothing removed. Babies may have more frequent bowel motions, and may cry a bit inside the incubator, but apart from that there are no major side effects.
When a baby is severely jaundice and brain damage imminent, paediatricians can bring down the bilirubin immediately with exchange transfusion to replace all the baby's blood-which is a much more risky procedure compared with phototherapy.
Prevention:
A mild degree of jaundice in a newborn is called physiological because it is physiologically normal. The emphasis therefore is on the prevention of baby's bilirubin level reaching toxic levels rather than eliminating jaundice in newborns at all costs.
The American Academy of Pediatrics advised that mothers should not put babies under direct sunlight to prevent jaundice, and should not choose the bottle instead of breast feeding for fear of jaundice. Although jaundice may last longer in babies fed on the breast, this can be minimized by nursing the baby more frequently: Once every two hours or so on demand. All too often, the so-called breast milk jaundice comes from ineffective lactation rather than the breast milk itself.
Babies born in Hong Kong would be tested at birth for G6PD deficiency-a common hereditary blood disease where the red blood cells are lacking an enzyme called G6PD, making them vulnerable to damage by some drugs, herbs and moth balls. When exposed, these babies can develop severe jaundice rapidly. Take note of the result of the test of your baby before you bring your baby home.
Babies who remain jaundiced after 3 weeks are uncommon, and should be seen by doctors to exclude diseases of the liver or bile ducts.
