When we think about diseases in India, dengue, malaria, diabetes, heart disease, tuberculosis and other common illnesses usually come to mind. But these are only a part of the country's health story. India is also home to diseases that many people may never have heard of until someone close to them is diagnosed. Some are spread by mosquitoes, ticks or sandflies, some come from animals or contaminated water, and others can follow an animal bite.

Some of these diseases are particularly difficult to recognise because their early symptoms can look like ordinary fever, flu or other common infections. This can delay diagnosis and treatment. India's disease surveillance system specifically tracks several such illnesses, including scrub typhus, leptospirosis, rabies, Kyasanur Forest Disease and Nipah virus disease. Here are some unusual but very real diseases that need more attention.

1. Melioidosis

Melioidosis is a bacterial infection caused by Burkholderia pseudomallei, a bacterium found in soil and water. It is sometimes called the "great mimicker" because its symptoms can resemble several other illnesses.

People can become infected through contact with contaminated soil or water, particularly through cuts in the skin, or by inhaling or swallowing contaminated material. Fever, cough, breathing difficulty, chest pain, joint pain and other symptoms may occur. In severe cases, the infection can spread through the body and cause pneumonia, blood infection or organ failure. Research in Odisha has highlighted the substantial health burden of the disease in South Asia, even though melioidosis is not currently included in the WHO list of neglected tropical diseases.

2. Scrub Typhus

Scrub typhus is caused by the bacterium Orientia tsutsugamushi and is spread through the bite of infected mites. It is present across several parts of India and is particularly important during and after the rainy season.

The illness can begin with high fever, headache, body aches and weakness. Some patients develop a dark, scab-like mark called an eschar at the site of the bite, although this is not always present. Severe cases can affect the lungs, brain, kidneys or other organs. One reason scrub typhus is dangerous is that its early symptoms overlap with dengue, malaria and other causes of fever. It is therefore important for doctors to consider it when someone has persistent fever, especially after exposure to vegetation or rural environments. The US CDC notes that scrub typhus is the most common rickettsial infection among rickettsial diseases reported in India.

3. Nipah Virus

Nipah virus is a rare zoonotic infection that has repeatedly appeared in India, particularly in Kerala, and has also caused outbreaks in West Bengal. Fruit bats are the natural hosts of the virus. People can become infected through contact with infected animals or contaminated food, and person-to-person transmission can occur through close contact with an infected individual.

Nipah can initially cause fever, headache, vomiting and breathing problems, but severe disease can progress to encephalitis, seizures, coma and respiratory failure. WHO estimates the case fatality ratio in outbreaks across affected countries, including India, at around 40% to 75%. There is currently no licensed vaccine or specific treatment for Nipah, making early recognition and intensive supportive care particularly important.

4. Leptospirosis

Leptospirosis is a bacterial disease linked to animals, particularly rodents. The bacteria can enter the human body through cuts or abrasions in the skin or through the eyes, nose and mouth when a person comes into contact with contaminated water or soil.

It is especially relevant after heavy rainfall and flooding. Symptoms may include sudden fever, chills, headache, muscle pain and red eyes. Severe infection can cause jaundice, kidney failure, breathing problems or bleeding. The disease is treatable, particularly when recognised early, but it can be mistaken for other causes of fever.

5. Kyasanur Forest Disease

Kyasanur Forest Disease, or KFD, is a viral infection first identified in Karnataka in 1957. It is transmitted mainly through infected ticks, with wild animals such as monkeys forming part of its natural cycle. People who enter forested areas can get exposed to infected ticks. Fever, headache, muscle pain and weakness may occur, and some patients develop bleeding or other serious complications.

KFD was initially associated with the forests of Karnataka, but infections have also been reported in neighbouring areas and Goa. WHO has described it as a tick-borne zoonotic disease, with outbreaks generally showing a seasonal pattern.

6. Kala-Azar

Visceral leishmaniasis, commonly known as kala-azar, is caused by a parasite transmitted by infected female sandflies. The name literally means "black disease". Unlike many infections that cause a short fever, kala-azar can lead to prolonged fever, weight loss, weakness and enlargement of the spleen and liver. Without treatment, severe disease can be fatal.

India has made major progress against kala-azar. WHO reports that cases have fallen dramatically over the past decades, but the disease continues to be relevant in parts of Bihar, Jharkhand, Uttar Pradesh and West Bengal.

7. Rabies

Rabies may not sound unusual, but its severity and the continuing number of cases make it one of India's most important neglected diseases. The virus is usually transmitted through the saliva of an infected animal, most commonly through a bite. Once clinical symptoms develop, rabies is almost universally fatal. However, death can be prevented if appropriate post-exposure treatment is started shortly after exposure.

WHO estimates that India has millions of animal bites every year and continues to record thousands of human rabies deaths annually. This makes one message important: a dog, cat, monkey or other potentially rabid animal bite or scratch should never be ignored.

8. Naegleria fowleri

Naegleria fowleri, also known as "brain-eating amoeba", is a microscopic organism that can cause a rare infection called primary amebic meningoencephalitis, or PAM. The organism is linked to warm freshwater. Infection can occur when contaminated water enters the nose, allowing the organism to reach the brain. It does not spread from person to person.

PAM is rare but can progress rapidly and become deadly. Since its early symptoms can resemble other forms of meningitis, diagnosis can be challenging.

9. Snakebite Envenoming

A snakebite may sound like an accident rather than a disease, but snakebite envenoming is recognised by WHO as a neglected tropical disease. In India, the "Big Four" responsible for a large proportion of serious bites are the Indian cobra, common krait, Russell's viper and saw-scaled viper. Venom can cause paralysis, severe bleeding, kidney damage and tissue destruction. Antivenom can prevent or reverse many dangerous effects when appropriate treatment is given promptly.

Why Do These Diseases Matter?

The biggest lesson is that a disease does not have to be common to be important. Many of these illnesses are linked to particular environments, seasons, occupations or animal exposures. A person living near forests may face risks that someone in a large city rarely encounters. Flooding can increase exposure to leptospirosis, while agricultural and forest workers may face greater risks from ticks, mites and snakes.

Another challenge is that many of these diseases start with ordinary-looking symptoms, especially fever. That can make diagnosis difficult and delay treatment. India continues to strengthen surveillance and disease detection, but awareness among the public is equally important.

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