Encephalitis fever in Bihar: From toxic lychees (litchis) to heat and humidity, here are various reasons behind brain viral infection
The broad characteristics of AES define it as a group of clinically similar neurologic manifestations caused by several different viruses, bacteria, fungus, parasites, chemicals or toxins etc, reports said.
Acute Encephalitis Syndrome or AES is a viral infection and is generally described as a bunch of diseases that include hypoglycemia, dyselectrolytemia, varicella (chickenpox), Japanese Encephalitis +ve and AES unknown
Young children and older adults are at greater risk of most types of viral encephalitis
High temperatures during summer, along with higher than normal humidity is considered to be an ideal catalyst for the outbreak of AES
On Monday, Union minister Harsh Vardhan set up a high-level multi-disciplinary team to be sent to Bihar for undertaking necessary groundwork to set up a state-of-the-art research centre at Muzaffarpur to find out the cause of the viral encephalitis fever and help tackle the spread of disease which has claimed 104 lives so far this year in Bihar.
Acute Encephalitis Syndrome or AES is a viral infection and is generally described as a bunch of diseases that include hypoglycemia, dyselectrolytemia, varicella (chickenpox), Japanese Encephalitis +ve and AES unknown. The broad characteristics of AES define it as a group of clinically similar neurologic manifestations caused by several different viruses, bacteria, fungus, parasites, chemicals or toxins etc., reports said.
Also, encephalitis occurs in two types:
Primary encephalitis: This involves a virus, fungus or bacterium directly infecting the brain. It could also be that the infection may be a reactivation of the virus after a previous illness.
Secondary encephalitis: This can occur due to the immune system responding to a previous infection and mistakenly attacking the brain. Secondary encephalitis often occurs two to three weeks after the initial infection.
The general symptoms of encephalitis are fever, headache, poor appetite, loss of energy. But severe cases can show signs of nausea and vomiting, stiff neck, confusion, personality changes, convulsions (seizures), problems with speech or hearing, hallucinations, memory loss, drowsiness and also coma.
However, various reasons are being attributed to the epidemic in Bihar. Some experts have said that eating locally cultivated lychees is causing the disease in children, other doctors contend it is being aided by an intense heatwave and high levels of humidity in the region.
Is lychee the culprit?
An intensive study by experts from the National Centre for Disease Control (NCDC), New Delhi and the Center for Disease Control (CDC), Atlanta (USA) established a relation between hypoglycemia or low blood sugar, found in children with poor nutrition who sleep hungry, and methylene cyclopropyl-glycine (MCPG), a toxic chemical found in lychees that affects the brain due to undernourishment.
According to Gulf News's report, in 2015, US researchers had also said the brain disease could be linked to a toxic substance found in lychee. The outbreaks of the disease have happened annually during summer months in Muzaffarpur and neighbouring districts since 1995, coinciding with the lychee season. Similar outbreaks of neurological illness have been observed in lychee-growing regions of Bangladesh and Vietnam as well.
Heat and humidity as catalysts
However, doctors in India are pointing out the role of rising heat in the northern regions of the country and delayed monsoon as one of the main reasons. News18 spoke to Gopal Shankar, the acting HOD of the Sri Krishna Medical College and Hospital Muzaffarpur to understand the recent trend and he claimed that the deaths occurred due to “acclimatisation failure in children” and were caused by “environmental factors” such as the heatwave and poor rainfall in the area. “Earlier people thought that the outbreak is caused by a virus. But it is a case of heat stroke causing these deaths. In the years 2005, 2011, 2013, 2014 and 2019, when temperature and humidity were recorded over consecutive days at more 38 degrees Celsius and 50 percent respectively, the epidemic had been at its worse with over 700 dying in 2014 alone,” he told News18.
In other parts of north India, there is fluctuation in temperature and humidity, and the nights are cooler, but in Muzaffarpur humidity increases at night making it worse than the day, especially for children, Shankar was quoted as saying.
“When it rained a few days ago, the following day witnessed a drop in the number of AES patients in the hospital. Now when it hasn’t rained, the numbers are increasing,” he said.
The report says that Shankar also refuted the lychee theory stating that the sick children did not show symptoms of abdominal pain to prove the role of the fruit.
However, the report cites the lack of early and preventive care to poor children caused due to delays in bringing them to the hospital, which leads to most deaths as the fever spreads to the brain.
“Children suffering from fever and convulsion early in the morning are brought to health centres after 6-8 hours," the SKMCH doctor said. In fact, in this regard, the NHRC has taken note that epidemic is a case of human rights violations of the victim children and their families.
The National Health Portal of India says encephalitis is mostly caused due to the Japanese Encephalitis (JE) virus which was clinically diagnosed in India for the first time in 1955 in the southern State of Madras (now Tamil Nadu) and later also reported in Bihar. India launched a JE vaccination programme in 2006, which in 2014 became part of the National Immunisation Programme.
The Japanese Encephalitis virus (JE virus) is transmitted to humans through bites from infected mosquitoes of the Culex species. The virus exists in a transmission cycle between mosquitoes, water birds and animals. JEV is transmitted mainly during the warm season, which can be cited as one of the reasons for the epidemic breaking out in hot and humid climatic conditions.
Other viruses also cause encephalitis
Common viruses, including HSV (herpes simplex virus) and EBV (Epstein-Barr virus), other childhood viruses, including measles and mumps and Arboviruses (spread by mosquitoes, ticks, and other insects), including Japanese encephalitis, West Nile encephalitis, and tick-borne encephalitis also cause the disease.
According to doctors, high temperatures during summer, along with higher than normal humidity is considered to be an ideal catalyst for the outbreak of AES.
Even infection with the rabies virus, which is usually transmitted by a bite from an infected animal, causes a rapid progression to encephalitis once symptoms begin. Rabies is a rare cause of encephalitis in the United States.
Some types of encephalitis are more common or more severe in certain age groups. In general, young children and older adults are at greater risk of most types of viral encephalitis. Also, people who have HIV/AIDS, take immune-suppressing drugs or have another condition causing a weakened immune system are at increased risk of encephalitis.