India is investigating if organochlorines caused the mystery illness that struck at least 400 and killed one in Andhra Pradesh this past week. Health officials revealed on Tuesday that those who exhibited symptoms of the unknown disease tested negative for COVID-19.

More than 400 children in the state of Andhra Pradesh were rushed to hospitals in the past few days after suffering from dizziness, fainting spells, headache, and vomiting. A 45-year-old man also died from the disease over the weekend.

The cause of the disease remains unknown but experts suggest it could have been caused by organochlorine, a poisonous substance used as a pesticide or mosquito repellant. Federal lawmaker GVL Narasimha Rao revealed on Twitter that she had spoken with medical experts and found that organochlorine might be the most likely cause of the infections.

Public health director Geeta Prasadini also said they were awaiting test reports to establish the cause of the mystery illness. “It is one of the possibilities,” she said, referring to organochlorines.

On Dec. 7, Andhra Pradesh Chief Minister YS Jagan Mohan Reddy visited the Government General Hospital in the state and assured all the affected individuals that they would receive help from the government. He later addressed a high-level review meeting and directed officials to handle the outbreak effectively and stay on full alert.  

Research has found that organochlorines could cause cancer and other potential risks. While the substance is banned in many countries, it is not in India. In fact, some of the pollutants have remained in the Indian environment for years and have built up in animal and human fat.

Organochlorines were previously used to control malaria and typhus. However, the use of the substance was later banned after it was found that it could cause several adverse effects in the central and peripheral nervous system.

According to research, exposure to pesticides with organochlorine over a short period could cause convulsions, headache, dizziness, nausea, vomiting, tremors, muscle weakness, salivation, sweating, confusion, and slurred speech.

India Coronavirus Swab Test A medical staff wearing Personal Protective Equipment (PPE) takes a throat swab sample from a man during a Covid-19 Coronavirus screening at a quarantine center. Photo by INDRANIL MUKHERJEE/AFP via Getty Images