The Nipah virus can be transmitted from animals, like pigs and fruit bats, to humans. It can also spread person-to-person through contaminated food.

The World Health Organization has described Nipah in its top ten priority diseases, along with pathogens like Covid-19 and Zika, because of its potential to trigger an epidemic.

The incubation period ranges from four to 14 days.

People who contract the virus show a wide range of symptoms, or sometimes, none at all.

Initial symptoms may include fever, headaches, muscle pain, vomiting and sore throat. In some people, these may be followed by drowsiness, altered consciousness, and pneumonia.

Encephalitis, a sometimes-fatal condition that causes inflammation of the brain, may occur in severe cases.

To date, no drugs of vaccines have been approved to treat the disease.

The first recognised Nipah outbreak was in 1998 among pig farmers in Malaysia and later spread to neighbouring Singapore. The virus got its name from the village where it was first discovered.

More than 100 people were killed and a million pigs culled in an effort to contain the virus. It also resulted in significant economic losses for farmers and those in the livestock trade.

Bangladesh has borne the brunt in recent years, with more than 100 people dying of Nipah since 2001.

The virus has also been detected in India. Outbreaks were reported in West Bengal in 2001 and 2007.

More recently, the southern state of Kerala has been a Nipah hotspot. In 2018, 19 cases were reported of which 17 were fatal; and in 2023, two out of six confirmed cases later died.

At least five confirmed cases were reported as of last week, all of whom were linked to a private hospital in Barasat. Two nurses are being treated in an intensive coronary care unit, one of whom remains in “very critical” condition, local media reported citing the state’s health department.

No cases have yet been reported outside India, but several countries are stepping up precautions.

On Sunday, Thailand started screening passengers at three international airports in Bangkok and Phuket that receive flights from West Bengal. Passengers from these flights have been asked to make health declarations.

The parks and wildlife department has also implemented stricter screenings in natural tourist attractions.

Jurai Wongswasdi, a spokeswoman for the Department for Disease Control, told BBC Thai authorities are “fairly confident” about guarding against an outbreak in Thailand.

Nepal, too, has begun screening people arriving through the airport in Kathmandu and other land border points with India.

Meanwhile, health authorities in Taiwan have proposed to list the Nipah virus as a “Category 5 disease”. Under the island’s system, diseases classified as Category 5 are emerging or rare infections with major public health risks, that require immediate reporting and special control measures.

Von der Leyen and European Council President António Costa are in Delhi, where they met Modi at a bilateral summit.

The European Commission said the agreement would eliminate tariffs on most exports of chemicals, machinery and electrical equipment, as well as aircraft and spacecraft, following phased reductions. Significantly, duties on motor vehicles, currently as high as 110%, would be cut to 10% under a quota of 250,000 vehicles. That is six times larger than the 37,000-unit quota India granted to the UK in a deal signed last July, Bloomberg reported.

India’s deal with the EU is set to lower costs for European products entering the country – such as cars, machinery and agricultural food items, after import duties are reduced.

Brussels said the agreement would support investment flows, improve access to European markets and deepen supply-chain integration.

Delhi said almost all of its exports would get “preferential access” into the EU, with textiles, leather, marine products, handicrafts, gems and jewellery set to see a reduction or elimination of tariffs.

While commodities such as tea, coffee, spices and processed foods will benefit from the agreement, Delhi “has prudently safeguarded sensitive sectors, including dairy, cereals, poultry, soy meal, certain fruits and vegetables, balancing export growth with domestic priorities”, it said.

Delhi and Brussels have also agreed on a mobility framework that eases restrictions for professionals to travel between India and the EU in the short term.

“This is India’s biggest free trade agreement,” Modi said. “It will make access to European markets easier for India’s farmers and small business. It will also boost manufacturing and services sectors. It will boost innovative partnerships.”

The trade deal comes as both India and the EU contend with economic and geopolitical pressure from the US.

Delhi is grappling with 50% tariffs imposed by President Donald Trump last year amid talks aimed at securing a trade deal between India and the US that are still dragging on.

Last week, Trump threatened to escalate his trade war with European allies for opposing a US takeover of Greenland, before backing off.

That larger geopolitical context was evident in statements made by leaders.

On Tuesday, von der Leyen said: “This is the tale of two giants – the world’s second and fourth largest economies. Two giants which chose partnership in a true win-win fashion. A strong message that co-operation is the best answer to global challenges.”

A day before that Costa had said, without naming the US, that the trade deal would send an “important political message to the world that India and the EU believe more in trade agreements than in tariffs” at a time when protectionism is on the rise and “some countries have decided to increase tariffs”.

Von der Leyen and Costa arrived in Delhi over the weekend and were the chief guests at India’s colourful Republic Day celebrations on Monday.

On Tuesday, the leaders posed for photos with Modi, with the bonhomie between them evident.

The formal signing is likely to take place only later this year, after the agreement is approved by the European Parliament and the European Council.

Alongside the trade agreement, India and the European Union are also advancing separate talks on security and defence co-operation, and climate action.

On Tuesday, India’s Defence Minister Rajnath Singh said he had discussed a range of bilateral security and defence issues with the European Commission’s vice-president Kaja Kallas, including opportunities to integrate supply chains to build trusted defence ecosystems and develop future-ready capabilities.

The two sides are working on a draft security and defence partnership covering areas such as maritime security, cyber threats and defence dialogue, Reuters news agency reported.

The EU is India’s largest trading partner in goods, with bilateral merchandise trade reaching $136bn (£99.4bn) in 2024-25, nearly doubling over a decade.

Talks for a deal between them started in 2007 but stalled in 2013 over roadblocks in market access and regulatory demands. Discussions were formally restarted in July 2022.

Officials from both sides worked hard over the past few days to finalise outstanding chapters of the agreement, aiming to wrap it up before the EU leaders’ visit.

The agreement comes as pressure grows on Delhi and Brussels to secure alternative markets for exporters.

In the past seven months, India signed major trade agreements with the UK, Oman and New Zealand, and a 2024 pact signed with the four-nation European Free Trade Association bloc of Switzerland, Norway, Iceland and Liechtenstein has come into effect. It signed a trade pact with Australia in 2023.

The EU, meanwhile, signed a trade deal with South American trade bloc Mercosur earlier this month after 25 years of negotiation.