The Union Ministry of Health releases weekly reports on outbreaks as part of the Integrated Disease Surveillance Programme (IDSP). The data, available for the period from June 2009 to November 2024 indicates that the number of cases related to fevers, flu, and respiratory illnesses are back to pre-COVID levels after a notable dip in 2020.
The emergence of the new Human Metapneumovirus (HMPV) has reignited concerns about respiratory infections and their impact on public health, particularly in a post-COVID world where vigilance around such illnesses has heightened. Concerns escalated following media reports of an HMPV outbreak in China, which drew global attention due to its timing during the peak respiratory illness season. While HMPV is not a new virus, it has recently gained attention due to an uptick in cases reported globally, including in India. The virus was first identified in 2001.
The Indian Council of Medical Research (ICMR) has confirmed isolated cases through routine surveillance. At the same time, the Union Health Ministry has assured the public that there is no cause for alarm, emphasizing the nation’s preparedness. Similarly, the World Health Organization (WHO) has highlighted that current infection levels are within expected seasonal norms and are predominantly mild in nature.
Nonetheless, the Health Ministry has asked states and union territories to enhance surveillance efforts for respiratory illnesses, including Influenza-like Illness (ILI) and Severe Acute Respiratory Infections (SARI). Additionally, states have been asked to raise awareness about preventing the spread of Human Metapneumovirus (HMPV) following the detection of five cases in India.
In this backdrop, we examine the data on infectious diseases reported in India over the past decade. This includes an analysis of reported diseases, with a focus on fevers and respiratory illnesses, their seasonal trends, and the state-wise distribution of cases. By identifying patterns in outbreaks, understanding the burden of respiratory diseases, and highlighting geographical hotspots, this story seeks to highlight trends that can inform public health strategies and provide insights into improving preparedness and addressing challenges in managing such public health concerns.
The data for the story has been sourced from Dataful, collated from the weekly reports on outbreaks released as part of the Integrated Disease Surveillance Programme (IDSP). The data is available for the period from June 2009 to November 2024.
An average of 52 cases of acute diarrheal disease and 39 cases of food poisoning were reported daily between 2010 and 2023
Cases of infectious diseases such as cholera, measles, mumps, chikungunya, and dengue are reported every year, which can be attributed to several factors. Factors such as mosquito breeding during the monsoon, India’s tropical climate, and poor sanitation and hygiene contribute to this. While many of these diseases are preventable, the measures for prevention vary. In the following chart, the trends in cases of some of these diseases have been given. These diseases roughly accounted for 75% to 93% of the reported cases in the last 9 years.
Data for roughly 11 months in 2024 reveals a surge in reported cases of mumps, acute diarrheal disease, hepatitis A, and cholera. Data indicates that an average of 18,826 cases of acute diarrheal disease and 14,236 cases of food poisoning were reported between 2010 and 2023. This roughly translates to 52 and 39 cases reported daily.
Furthermore, between 2020 and 2022, there was a noticeable decline in the reported cases of these diseases, as well as a reduction in overall numbers compared to previous years. This could potentially be attributed to the prominence of COVID-19 during this period, which not only shifted healthcare priorities but also led to stricter public health measures such as lockdowns, improved hygiene, and limited mobility, inadvertently reducing the spread or reporting of other infectious diseases.
Reported cases of some fevers and flus have spiked since 2020
Focusing specifically on cases related to fevers, flus, and respiratory illnesses, the data reveals a notable dip in 2020. However, since 2021, the figures have returned to pre-2020 levels. Trends related to some of the commonly reported flu, fever, and respiratory illnesses have been provided in the chart below. Not all these diseases got reported every year.
Fever of Unknown Origin/Cause got reported (reappeared) in 2023 and 2024 after 2010. Over 305 cases in 2023 and 62 cases in 2024 were reported in the said category. 2024 also saw cases of ARI Influenza like Illnesses reported after a long gap of 8 years.
Between 2017 and 2020, less than 100 cases of fevers with rash were recorded which increased since 2021. More than 2000 cases have been reported since. 2020 and 2021 also recorded a spike in H3N2 (Influenza A virus subtype H3N2) cases.
West Bengal, Maharashtra, Gujarat, MP reported relatively higher number of cases
State-wise distribution of these respiratory illnesses and fevers reveals that Maharashtra, Karnataka, Madhya Pradesh, Gujarat, West Bengal, Kerala, and Tamil Nadu reported the greatest number of cases. In Maharashtra, more than 1 lakh cases of swine flu were recorded in 2015. Likewise, the other states also saw a higher number of cases reported in the same year due to the same disease. Even if we don’t consider 2015 figures, these states report a higher number of cases of both respiratory/fever like illnesses. If all diseases are considered, West Bengal, Maharashtra, Karnataka, Madhya Pradesh, Gujarat, Kerala, and Assam recorded a relatively higher number of cases.
The higher incidence of respiratory illnesses and fevers in states like Maharashtra, Karnataka, Madhya Pradesh, Gujarat, West Bengal, Kerala, Tamil Nadu, and Assam can be attributed to possible factors such as high population density, tropical climates, and seasonal outbreaks that facilitate disease transmission. Other contributing factors may include better healthcare infrastructure and reporting systems.
Most respiratory illnesses or fevers were reported in India in the ‘post monsoon’ season
To understand the seasonality of respiratory diseases, flus and fevers, we have categorized the weekly data as follows:
Season | Months |
Winter | December to February |
Summer | March to May |
Monsoon | June to August |
Post Monsoon | September to November |
The post-monsoon season or ‘autumn’ is the time when most respiratory illnesses or fevers and flu get reported in India, unlike winter in Europe and the USA. Data for 2009 to 2023 reveals that more than 30% of the cases were reported between September and November in 11 out of 15 years. Since 2020, the number of cases reported has been highest in different seasons in each year.
After 2016, the share of cases during Monsoon months fluctuated significantly, with a steep drop in 2020 and accounting for nearly half the cases in 2023. Meanwhile, Summer typically had the lowest share of cases, with the exception of 2013 (25.9%). In 2020, the share of cases in summer was quite high at 39.5%, which could be an anomaly due to changes in the reporting and disease dynamics during the COVID-19 pandemic. Winter generally has a moderate share of cases.
India should focus on enhancing routine disease monitoring, improving laboratory capacity for early detection, and raising public awareness about respiratory infections. Seasonal preparedness plans should address region-specific factors such as population density and climate.