Nipah outbreak in Kerala: Health professionals, scientists struggle to understand how virus reached Kozhikode

It has now been close to a week since the dreaded Nipah virus outbreak hit Kozhikode in north Kerala. The state government would like the rest of the world to believe that its efforts to contain the virus to as small an area as possible have been successful.

To a large extent, that claim does have merit. Even though one more person died on Saturday afternoon, the death was reported from Kozhikode itself.

But more attention needs to be given to the question as to how the virus outbreak happened in this part of the world. This is an issue which baffles health experts.

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It is unclear how the virus landed up in Kozhikode, which is close to three thousand kilometers away from Siliguri in West Bengal, where the last such outbreak was reported way back in 2001. Bangladesh, which saw several Nipah cases till 2017, is also a huge distance away from Kozhikode.

Health officials have been burning the midnight oil to ensure that the outbreak is contained. In a matter of further worry for them, test results from the National Institute of High Security Animal Diseases (NISHAD), Bhopal came in.

These results were from samples of the bats found in the well of a house in Perambra which is believed to be the epicentre of the outbreak. The Nipah virus was not found in these samples.

However, the bats whose samples were collected were insectivorous bats and not fruit bats, which are the only reported host carriers of Nipah till date.

While another round of efforts is on to catch hold of fruit bats in the area to send their blood and salivary samples for testing, at present, confusion prevails on the cause of the disease.

No such previous cases have ever been reported from anywhere in south India. So, this is perhaps for the first time that experts are faced with such an unprecedented situation.

People wear safety masks as a precaution against the Nipah virus. File image. PTI

Doctor K Abdul Gafoor is an infectious disease specialist at the Apollo Specialty Hospital in Chennai and had been camping in Kozhikode for the past week trying to ascertain how the virus came here.

“Of course, we have no idea at the moment. We need a detailed epidemiological study to get anywhere close to a conclusion. But one positive aspect is that all this seems to be linked to one place which we believe is the source. There has been no second source so far, which in itself is a huge relief. Had there been a second source, things would have been different," Dr Ghafoor told Firstpost.

Dr Gafoor also added that the strength of the outbreak has decreased considerably and that the initial panic which the health officials faced has now given way to a new confidence that this is a disease which may not have a vaccine or a complete cure, but can be contained from spreading further.

The primary source that the doctor had referred to was the house at Chengaroth village in Perambra panchayat, where three people from a family — two brothers and their aunt — had died. While the absence of a secondary source brings relief, many doctors have a word of caution.

“This is why it is so important to find the source of this outbreak. Only if we answer the question of how the virus came to this part of the world can we put in place scientific measures to ensure that such an outbreak does not happen anywhere close by again. Otherwise, we cannot be sure of how and in which way this virus would spread in the future,’’ warns Dr Shimna Azeez, a medical officer at Malappuram, from where two confirmed cases of Nipah were reported apart from the ones at Kozhikode.

Following is an overview of the possible ways in which the virus could have travelled to northern Kerala.

From Bangladesh to Kerala?

Even though it is well known that fruit bats are the host carriers of the virus, no evidence could be gathered from Kozhikode to prove that the same species of bats have played a role in this outbreak too.

The assumption that fruit bats are the villains is based on the previous outbreaks that took place in Siliguri, Bangladesh, and Malaysia. But health officials say that as long as no conflicting evidence is received, it has to be believed that fruit bats are indeed the cause in Kozhikode too.

But even that also does not answer the crucial question — how did the virus reach Kerala?

Although some species of bats have been found to be migratory, scientists are not ready to believe that they would have flown thousands of miles to northern Kerala without showing such viral activity at any place on their way.

There are a few who propose another theory. According to them, other large carnivorous migratory birds like eagles may have preyed upon an infected fruit bat and brought the virus with them in their bodies to Kerala. They may have then attacked a fruit bat in the state.

Although this is theoretically possible, wildlife experts say it is improbable. “There has been no evidence so far to prove that such large migratory birds are capable of carrying the virus, simply because their body constitution does not support Nipah. This virus thrives in solutions which are high in sugar content, like the saliva of a fruit bat. That is why we say it cannot be even in insectivorous bats. We cannot at this moment think of any other bird as a host,’’ well known ornithologist Dr R Sugathan told Firstpost.

Food source?

But Sugathan has another interesting take. He says that it is possible that Nipah could have traveled in fruits like figs and dates from places like Bangladesh to Kerala. But here too, the role of the bats is the key.

“There are lots of dates that come from outside. We all know that dates are very high in sugar content. There is a possibility that some infected fruit bat could have come in contact with dates while being packed. Since this virus has the capacity to survive for a number of days in a sugary medium, we cannot rule out this possibility,’’ added Sugathan.

Sugathan’s theory also makes sense because it is the month of Ramzan, and in Kozhikode, dates arrive in huge quantities from a number of countries outside India.

No outside source?

While scientists are battling hard to find an external source of the virus, some believe that Nipah could have co-existed with the bats in Kozhikode for a long time only to be pushed out of the mammal in adverse circumstances.

Dr Nameer PO is the head of the department at College of Forestry in Kerala Agricultural University, and is an expert on bats. He says that such viruses and ‘flying foxes’ have always been co-existing entities, and it was only a matter of time that they showed up to the rest of the world.

“Viruses like Nipah have always been in the system of fruit bats. They have co-evolved for years. Such a disease becomes virulent when there is a stress on the animal. Such stress could be because of a loss of habitat, or not getting sufficient food for survival. So, when the animal is faced with such stress, it tends to expel these viruses. In other words, the virus tends to move out of animal. This could be what happened in Kozhikode. But unless we get conclusive evidence that such bats are the reason, we cannot be sure,’’ Nameer told Firstpost.

Nameer also cites the example of the co-existence of migratory birds and the avian bird flu virus. According to him, since these birds are migratory in nature, they take it from one location to another.

Scientists are also raising the question of mutation. In other words, they say that depending on changes in many external factors like temperature and water, some of the viruses may break up or even mutate into different forms and get transformed into a new and highly virulent one such as Nipah and lead to an outbreak.

“There is a serious possibility that mutation could have been the reason for an outbreak in Kozhikode. But that can only be ascertained with an in-depth study, which will take a number of days,’’ added a senior doctor in the team of experts camping at Kozhikode.

Some doctors say that while dealing with a disease which has recently become known like Nipah, confusion is an expected thing. The medical fraternity is yet to understand Nipah in its entirety.

“It was first detected in 1998, which in the medical world means it is a new disease, about which there could be more things we don’t know than things we know. Remember, smallpox came to the world three thousand years ago, but we discovered a vaccine for it just 200 years ago. Nipah is a disease that was discovered just 20 years ago. The medical fraternity has recently started its research on it. But Kerala has done a commendable job in diagnosing it quickly,’’ said Dr PS Jinesh from Info Clinic.

Travel records of the first victim, Muhammed Salih, were also checked on Saturday to ascertain whether he had visited any of the areas reported to have had Nipah outbreaks in the recent past. Apart from visiting Dubai a few months ago, it seems that the young man had not travelled anywhere out of Kozhikode.

Meanwhile, the state has put in stringent control measures at the Kozhikode Government Medical College Hospital, where most of the Nipah cases have been reported. Only patients requiring emergency treatment are admitted at the hospital. Others are treated at the emergency section and discharged at the earliest to ensure that more patients do not come in contact with the virus.

Perhaps the only way to get to the bottom of this is to check as many samples of fruit bats as possible, a much-needed but painfully slow process that will start on Monday. Till then, the question of Nipah’s origin in Kerala will remain a matter of speculation.