Kozhikode: The Nipah virus infection that claimed two lives in 12 days in Kozhikode could have remained undiagnosed for a longer period because symptoms did not match with the ones reported in the 2018 outbreak that claimed 17 lives in the same city, said experts.

In the May 2018 outbreak, patients showed symptoms of encephalitis, or inflammation of the brain, said Dr Anoop A S, a critical care specialist in Aster MIMS, Kozhikode, and an expert in infectious diseases in ICU. Then, patients who checked in reported neurological symptoms such as seizures, inability to think clearly or concentrate, involuntary shaking of limbs (convulsions), and loss of consciousness, he said.

"This time, all patients have respiratory symptoms, progressing into bronchopneumonia (constricted airways) and then going into hypoxia (insufficient oxygen)," he told News Brake, Onmanorama's explainer podcast. It is difficult to identify the cause because there is already an influenza outbreak in Kozhikode during the monsoon and most of the patients have fever, cough, and breathing difficulties.

In fact, one private hospital, where the first patient died of bronchopneumonia on August 30, completely missed the Nipah virus infection. It ran tests only for common influenza and COVID-19, and the body was released to the family.

Around the world, around 650 cases of Nipah virus infection were reported. "And in all the cases, the early symptoms were neurological. This is the first time, Nipah infection is presenting with respiratory symptoms in the early stage," said Dr Anoop, credited with helping the early detection of the Nipah outbreak in 2018.

This time too, he played a key role in detecting the virus.

On September 10, two siblings aged nine and four years, their 22-year-old uncle and nine-month-old cousin were brought to Aster MIMS in Kozhikode. All of them had fever, and cough and were developing severe breathing difficulties. One child showed symptoms of bronchopneumonia.

The MIMS team, led by Dr Anoop, found the siblings' father 49-year-old Mohammed Ali, a native of Maruthonkara grama panchayat, died in another private hospital on August 30, and the causes of death were mentioned as bronchopneumonia and multi-organ failure. 

The MIMS doctors then held talks with the doctors who treated Mohammed Ali in the private hospital. Their meticulus questioning elicited previously ignored symptoms of Ali. The doctors told the MIMS team that he had slurred speech, double vision, and was a bit confused in the later stages of his illness.

Around the same time, the elder son of the man started developing seizures. "We realised we have a cluster and an index case and the usual symptoms. They are from the same area which was the epicentre of the Nipah outbreak in 2018," said Anoop.

Their village Maruthonkara was only 5km from Janaki Forest, a 324-acre woodland named after diplomat-politician V K Krishna Menon's daughter V K Janki Amma, who owned the land before the government took it. The forest is home to many bat species. During the 2018 Nipah outbreak, fruit bats from Janaki Forest tested positive for the Nipah virus.

MIMS doctors did not waste time. They isolated the four patients. Screen tests found the Nipah virus. They sent the samples for confirmation to the National Institute of Virology in Pune.

On September 11, 12 days after Mohammed Ali died, another patient, a 40-year-old man from Ayanchery grama panchayat was brought to Aster MIMS from another hospital. He had a cough for three days and developed breathing difficulties and hypoxemia, which is low oxygen level in his blood. He suffered a cardiac arrest soon after his arrival and died.

Though Ayanchery was 20km west of Maruthonkara grama panchayat, MIMS doctors had a strong suspicion about Nipah infection. They checked his history and found he was a caregiver to a relative in the same private hospital where Mohammed Ali died. "He was in the hospital on August 28 and 29, the same time when the first patient was undergoing treatment in the ICU," said Dr Anoop.

MIMS did not hand over the body of the 40-year-old patient to the relatives and alerted the health officials. They did a screen test and found it was the Nipah virus. They sent the samples to the National Institute of Virology in Pune for confirmation.

Virologist Rajendra Pilankatta, a professor at the Central University of Kerala's Department of Biochemistry and Molecular Biology, said the virus should be sequenced to find if it had mutated. "The Malaysia strain does not spread from person to person. But the Bangladesh strain does. In Kerala, it is the Bangladesh strain. Both strains were found in Thailand. Infected pigs show more respiratory symptoms. Encephalitis is seen more in humans," said Prof Pilankatta, an expert in the core committee of the Institute of Advanced Virology, Thiruvananthapuram.

Nipah has been reported in Kerala almost every year since 2018 when 17 lives were lost. In 2019, one case was reported in Ernakulam. In 2021, a 12-year-old boy died of encephalitis in Kozhikode.

Prof Pilankatta said constant health surveillance of the area and survey of flora and fauna can help find the origin of the infection.

The survey is important to find if there has been any change in the biodiversity of the area, which is aiding the spread of the virus. Direct contact of humans with fruit bats could be few and far between, he said. "But there could be intermediary hosts such as pigs and dogs or material such as some exotic fruits or crops through which the infection is spreading in the first place. We know farming on the fringes of the forest is common there," he said. Since the Nipah is a stable virus, it can stay alive for three days in fruit juice and two days in bat urine.

He said constant surveillance such as testing of residents can narrow down the source and their primary contact. "Follow-up action is a must and we are lacking in that," he said.