Meteorological Conditions Associated with AES/JE Outbreak 2019 in Bihar - Open Journal Systems
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Indian Journal of Public Health Research & Development, July 2020, Vol. 11, No. 7 765
Meteorological Conditions Associated with AES/JE Outbreak
2019 in Bihar
SC Bhan1, Anand Shankar2, Ragini Mishra3, GS Shilpashree4
1
Scientist F, India Meteorological Department, New Delhi, 2Scientist B, India Meteorological Department,
Patna, 3State Surveillance Officer, IDSP, State Health Society, Bihar, Patna, 4Senior Research Fellow, India
Meteorological Department, New Delhi
Abstract
Analysis of the incidences of AES during 2019 over Bihar brought out the highest incidence of AES cases in
June (78.5%) followed by July (12.6%). A similar pattern was found in the number of deaths associated with
AES. Maximum incidences were reported from Muzaffarpur (559) and East Champaran (113) districts in
north Bihar; and Gaya in south Bihar (72). More than 50% of the incidences and deaths were reported from
children up to the age of 5 years; and more than 90% from children up to the age of 10 years indicating high
vulnerability of children. Female children were found to be impacted more with 53% of the total incidences
and 58% of the total deaths.
The highest percentage of AES cases (78.5%) were reported in June followed by July (12.6%). The highest
percentage of deaths were reported in June (69.5%) followed by July (19%). An analysis of the incidences of
AES cases in the worst affected district (Muzaffarpur) shows a high degree of correlation with the maximum
temperature of the past few days. A second-degree polynomial best described the relationship between the
mean maximum temperature of the last two days and the incidence of AES cases in Muzaffarpur district
(R2=0.74).
Keywords:- Mean Maximum Temperature, Acute Encephalitis Syndrome, AES, Heat Index, Monsoon, Bihar,
Muzaffarpur
Introduction remains unknown in 68-75% of patients4. The history
of AES in India is documented in association with JE,
Acute Encephalitis Syndrome (AES) defined as acute
with the virus first being reported from southern India
onset of fever and a change in mental status including
in 1955. The sources of viral infection resulting in AES
symptoms such as confusion, disorientation, or inability
may differ across regions5. The most common of AES is
to talk and/or new onset of seizures excluding febrile
Japanese encephalitis (JE) - a vector-borne viral disease
convulsions is thought to be caused by a wide variety of
caused by the JE virus of group B arbovirus (Flavivirus)
conditions. Multiple factors like viruses, bacteria, fungi,
and is transmitted to humans by the Culicine Mosquito.
parasites, and toxins may cause AES1. It is estimated that
JE generally affects the central nervous system and
a population of 375 million is at risk of acquiring AES
can cause serious complications and death with a
in India2. Besides the JE virus, other viruses that have
high fatality rate6. The survivors may also experience
resulted in a high incidence of AES in India are Dengue
convulsions, episodic headache, abnormal behavior,
virus, Entero-virus, Herpes Simplex Virus, Measles
intellectual deficit, incoordination of movements, jerky
and Chandipura virus3. However, the etiology of AES
limb movements, speech disorder, cranial nerve palsy,
gaze palsy, parkinsonian features, impaired hearing, etc.
Corresponding Author: Incidence is high among the children due to a lack of
SC Bhan, Scientist F, immunity from natural infections. The disease has a high
India Meteorological Department, rate of death (about 25%) among the infected children.
Mausam Bhawan, Lodhi Road, New Delhi-110003 About 30% - 40% of the survivors suffer from physical
766 Indian Journal of Public Health Research & Development, July 2020, Vol. 11, No. 7
and mental impairment7. The disease was first recognized Warning Signals for the AES outbreak and thus help
in Japan in 1924. JE has been reported to be endemic in in the preparedness of the Health Sector to prevent any
large parts of the Asia and Pacific regions, especially in future impending outbreaks in the State.
the South Asian and Western Pacific regions8. Nearly
42% of 3187 reported cases of JE were from countries in Climate of Bihar
the South-East Asia region, with India alone accounting Bihar is a land-locked state that mainly comes under
for about 80% of these cases. JE has been identified the climate type subtropical monsoon, mild and dry
as the primary cause of the syndrome8. Tiwari et al. winter, hot summer except the districts of Jamui, Banka,
attributed a fatality rate of 30%–50% to JE in southern Munger, Lakhisarai, Khagaria, Sheikhpura and some
and eastern Asia. The outbreaks of JE in Gorakhpur parts of Bhagalpur, Saharsa and Begusarai located in
and Basti divisions in eastern UP during 2005, led to the extreme southeastern part of the State which comes
the development of surveillance guidelines for AES under the type Tropical Savanna, Hot seasonally dry13
and JE by the National Vector Borne Disease Control (usually winter). May is the hottest month with a mean
Programme (NVBDCP). These guidelines required JE maximum temperature of about 37OC in the plains.
to be reported as an AES and after confirmation from the The mean maximum temperature ranges from 34OC
sentinel sites, a line-list of JE cases needed to be drawn to 40.5OC over the state during May with the southern
and sent in prescribed formats9. Outbreaks of acute parts of the state being the hottest and the northern parts
encephalitis syndrome (AES) have occurred previously being the coldest. In January, the minima of the mean
in the northern regions of Bihar state and eastern minimum temperature are observed over the eastern
regions of Uttar Pradesh state of India. The first case region of the state. The skies are heavily clouded during
of AES in Muzaffarpur district was recorded in 1995. the South West Monsoon season (June-September),
Muzaffarpur district, suffers repeated epidemics of acute particularly during July and August13.
encephalopathy in children for the past 16-17 years.
Initially, the focus of the disease outbreak was limited The total average annual rainfall of the state is
to the Muzaffarpur district but the recent trend shows 1194.9 mm with an average of 50 rainy days.
that it has spread to many other districts in Bihar10.
The Southwest monsoon sets in over eastern parts of
Extreme heat and humidity of Muzaffarpur causing heat
the state by about the middle of the second week of June.
stroke leading to encephalopathy along with a sudden
July and August are the rainiest months, accounting
drop in cases when the rains set in and the temperatures
individually, to about 28% and 24% of the annual
dropped has also been reported in a study11. As per
rainfall, respectively. Withdrawal of the southwest
reports of State Surveillance Unit, IDSP, State Health
monsoon begins from the northern parts of the state in
Society Bihar, the peak of the AES outbreak in Bihar
the first week of October13.
has been observed in June that has been consistent since
the last five years12. The total cases & number of deaths Data and Methodology
reported in 2017, 2018 & 2019 in Bihar has been 268 &
56; 179 & 45, and 1089 & (236), respectively. In 2019, Bihar is one of the 36 Metrological subdivisions
AES cases were reported from 34 districts in the State. of India with four Departmental observatories at
The majority of the cases were reported during 2019 Patna, Gaya, Bhagalpur and Purnea, and seven part-
were from Muzaffarpur followed by East Champaran, time Observatories. Meteorological data from one of
Vaishali, and Gaya. The age group most affected was the observatories located in Muzaffarpur city has been
0-5 years (53.44%) and 5-10 years (37.37%). Females used for analysis in this study. Data on the incidence of
(53.16%) were more affected than males (46.83%). AES cases (known and unknown) and associated deaths
were collected from the daily reporting and monitoring
The present report informs about the epidemiology of of the cases being done by the State Surveillance Unit,
AES in Bihar as well as its meteorological interpretation. Integrated Disease Surveillance Programme. The
The report also highlights the use of meteorological program regularly shares the data with concerned district
data to establish co-relation with the AES outbreak. administration for proper and timely intervention to
The meteorological data may be used to generate Early control the disease outbreak (Source: State SurveillanceIndian Journal of Public Health Research & Development, July 2020, Vol. 11, No. 7 767
Unit, IDSP, State Health Society, Bihar). observed in the reported number of deaths with the
highest number of deaths (110) Muzaffarpur followed
Results and Discussion by Purbi Champaran (26), Vaishali (20), and Sitamarhi
Analysis (19). Gaya district in south Bihar reported 16 deaths.
The geographical distribution of total AES cases is given
Changes in weather patterns and precipitation affect in Figure 2. Similar distribution has been reported in the
the evolution of many infectious vector-borne diseases state earlier also13.
like Malaria, Chikungunya, Japanese Encephalitis,
Filariasis, etc. It has found that Acute Encephalitis Agewise and genderwise distribution:
Syndrome (AES), a deadly brain disease generally
Almost all of the 1081 AES cases were from the
affects children of age between 0-15 years. Normally,
Children aged between 0-15 years with maximum
the children experience symptoms like sudden falls
impacts on children in the age group of 0-5 years
in blood sugar which ultimately causes death. There
(53.2%). 37.6 % of cases were from the age group of
were a total number of 1089 AES known and AES
5 to < 10 years and 8.6% from 10 to < 15 years ago.
unknown cases reported across the Bihar during the
Only 3 cases of age 15 years or more were reported. Of
year 2019. Seven of these cases were from the adjoining
the 232 cases of AES related deaths, 52.6 % were from
state of Jharkhand and one from Nepal. Out of these
the age group less than 5 years, 38.4% from 5 to less
1081 cases, 232 (21.5%) cases reported death. Out of
than 10 years, and 8.2% from 10 to less than 15 years.
the total 715 known cases of AES, 554 (77.4 %) were
The highest number of deaths in all the age groups were
of Hypoglycemia and 130 (18.2%) were of Japanese
reported from Muzaffarpur district. Female children
Encephalitis. Out of all known cases of AES, 23.15 %
were found to be impacted slightly more by AES. Out
of patients died because of Hypoglycemia, Japanese
of the total 1081 reported cases, 46.8% were male and
Encephalitis, etc. A description of all the 1089 cases is
53.2% were female. Out of the total 232 AES related
given in Table 1.
deaths, 98 were male and 134 were female (Table 2).
Temporal Distribution:-
Relationship of AES incidence with temperature
Month-wise incidences of AES cases and associated in Muzaffarpur district:
deaths are given in Figure 1 below. The highest
As the highest number of cases were reported in
percentage of AES cases (78.5%) were reported in June
Muzaffarpur district, a detailed analysis of its relationship
followed by 12.6% in July and 3.2% in August. Similarly
with temperature carried out for Muzaffarpur district
the highest percentage of deaths were reported in June
for the month of June as the month accounted for about
(69.5%) followed by July (19%) and August (6%). The
90% of the cases. Correlation coefficients (CC) were
outbreak of AES occurred mainly from 4th June 2019
found between the incidences of AES and maximum
to 26th June 2019. The cases significantly decreased
temperature of the previous day; and the mean maximum
after the onset of Monsoon in Bihar (23rd June 2019).
temperatures of previous 2, 3, 4, 5, 6, and 7 days. The CC
This seasonal distribution is very similar, to the monthly
was 0.79 with the maximum temperature of the previous
pattern of AES in Bihar reported earlier14.
day; and 0.82 with the mean maximum temperature of
Spatial Distribution:- the previous 2 days. Correlation coefficients were also
computed between AES incidences and Heat Index for
Acute Encephalitis Syndrome (AES) cases were the day. The highest correlation coefficient of 0.56 was
reported from all parts of Bihar except the districts of found with the heat index of previous day. The plot
Gopalganj, Bhabhua, Khagaria, and Lakhisarai. Highest of the day to day incidences of AES against the mean
numbers of cases were reported from central districts maximum temperatures of the previous 2 days given in
of north Bihar, i.e., Muzaffarpur (559) followed by Figures 3 shows that the incidences of AES generally
Purbi Champaran (113), Vaishali (86) and Samastipur fluctuated with maximum temperatures. Scatter plot of
(57). Gaya district in south Bihar also reported a high AES incidences against the maximum temperature of
number of incidences (72). A similar pattern was also the previous day and the mean maximum temperature768 Indian Journal of Public Health Research & Development, July 2020, Vol. 11, No. 7
of the previous 2 days given in Figure 4 show that the Units of Measurements
number of AES cases increased exponentially with
Temperature:- Degree Celsius (ºC).
increase in temperature. A second degree polynomial
was found to best defines the variability in AES cases Abbreviations and Symbols
with an R2 value of 0.74. The average numbers of cases
were 2.6 cases on the days when maximum temperatures AES: - Acute Encephalitis Syndrome, JE: - Japanese
were 33 to 35 Deg C. These were 15.4 and 19.6 on days Encephalitis, JES: - Japanese Encephalitis Syndrome
with temperature 35 to 37 Deg C and 37 to 39 Deg C;
Table 1. Analysis of AES Cases in Bihar during 2019
Description Total Cases Deaths
Total AES 1089 236
Total AES Unknown 372 70
Total AES Confirmed 717 166
JE +ve 130 27
Meningitis/ Meningoencephalitis /Tubercular Meningitis/Pyogenic/Aseptic
6 0
Meningitis./Acute Meningococcal
Herpes/Measles/ Pox/Mumps/Viral Encephalitis 7 3
Hypoglycemia 554 134
Dyselectrolytemia 3 2
Chicken Pox 1 0
Others: Heatstroke, Hyper-pyrexia. 16 0
Table 2. Age and gender wise distribution of total AES cases
Age/Gender Number of AES Cases Number of Deaths
< 5 years 582 125
5 toIndian Journal of Public Health Research & Development, July 2020, Vol. 11, No. 7 769
Figure. 1. Monthwise distribution of AES cases and reported death of Bihar in 2019.
Figure. 2. Districtwise Distribution of AES cases in Bihar770 Indian Journal of Public Health Research & Development, July 2020, Vol. 11, No. 7
Figure. 3. Day to day incidences of AES cases in Muzaffarpur district and Mean Maximum Temperature of Previous 2 days
during June 2019
Figure. 4. Relationship between AES cases and Mean Maximum Temperature of Previous two days for Muzaffarpur, June, 2019
and 52.8 on days with temperature more than 39 Deg C.
Conclusion In the most affected district – Muzaffarpur, the
Analysis of AES incidence during summer 2019 incidences of AES was found to have a very high
brought out that maximum impact was on children in the correlation (0.82) with maximum temperature with a
age group of 0-5 years (53.2%) with only 8.6% from 10 lag of two days during the month of June. Increase in
to < 15 years ago. Of 232 cases of AES related deaths, number of AES cases with maximum temperature brings
52.6 % were from the age group less than 5 years. out a possibility that advance warning on temperatureIndian Journal of Public Health Research & Development, July 2020, Vol. 11, No. 7 771
could help the health system prepare better to combat 1143-1148.
the AES. 7. Government of India. Operational Guidelines:
National Programme for Prevention and Control
Ethical Clearance: Not Required
of Japanese Encephalitis/Acute Encephalitis
Source of Funding: Self Syndrome. National Vector Borne Disease
Control Programme, Directorate General of Health
Conflict of Interest: Nil Services, Ministry of Health and Family Welfare.
New Delhi. 2014.
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