Authorities in India's southern Kerala state are racing to contain an outbreak of the deadly Nipah virus.
The virus – which has a fatality rate of up to 75 percent - killed a 12-year-old boy in Kerala over the weekend, prompting ramped-up efforts to trace his contacts.
New infections have seen been confirmed.
Transmitted from animals to humans, the virus is found in contaminated food. People, once infected with Nipah can pass on to others.
The boy was admitted to a hospital a week ago with high fever. As his condition worsened and doctors suspected inflammation of his brain (encephalitis), his blood samples were sent to the National Institute of Virology, where tests confirmed a Nipah infection. He died early on Sunday.
Government authorities have stepped up contact tracing efforts, identifying, quarantining and testing people who may have come into contact with the victim.
According to the state's health minister, Veena George, 188 people who came into contact with the boy had been identified by Monday, CBS News has reported.
Of them, 20 were considered high-risk primary contacts — primarily his family members, all of whom were being held under strict quarantine or hospitalized.
Two healthcare workers who came into contact with the victim were already showing symptoms of Nipah infection by Monday.
They were admitted to a hospital and their blood samples sent for testing.
Authorities have since sealed off the area within about a two-mile radius of the boy's home, and they were screening people for symptoms in all adjoining districts of Kerala state. The neighboring state of Tamil Nadu was also on high alert for any suspect cases of fever.
This is the second time in three years that a Nipah virus outbreak has been reported in Kerala, which is also suffering from a high rate of COVID-19 infections.
Over the past 22 years, sporadic outbreaks of the Nipah virus, an emerging infectious disease, has prompted concern among international virologists and health officials.
First recognized in 1999 during an outbreak among pig farmers in Malaysia, the virus was, over the next few years, reported across Asian nations.
But what is the virus?
In infected people, according to the World Health Organization (WHO), the Nipah virus causes a range of illnesses from asymptomatic (subclinical) infection to acute respiratory illness and or fatal causes of encephalitis, or inflammation of the brain. The usual treatment is supportive care.
During the first recognized outbreak in Malaysia, which also affected Singapore, most human infections resulted from direct contact with sick pigs, or their contaminated tissues.
In later outbreaks in Bangladesh and India, consumption of fruits or fruit products (such as raw date palm juice) contaminated with urine or saliva from infected fruit bats was the most likely source of infection.
Human-to-human transmission of Nipah virus has also been reported among family and care givers of infected patients.
Risk of infection in other regions is possible, as evidence of the virus has been found in the known natural reservoir (Pteropus bat species) and several other bat species in a some countries, including Cambodia, Ghana, Indonesia, Madagascar, the Philippines, and Thailand.
During the later outbreaks in Bangladesh and India, Nipah virus spread directly from human-to-human through close contact with people’s secretions and excretions.
In Siliguri, India in 2001, transmission of the virus was also reported within a health-care setting, where 75 percent of cases occurred among hospital staff or visitors. From 2001 to 2008, around half of reported cases in Bangladesh were due to human-to-human transmission through providing care to infected patients.
An outbreak of the Nipah virus in India’s southern state Kerala in 2018 claimed 17 lives. At the time, countries, including Saudi Arabia and the United Arab Emirates temporarily banned frozen and processed fruit and vegetable imports from Kerala as a result of the outbreak there.
At the time, health officials believed that Nipah outbreaks in Bangladesh and India were perhaps associated with the drinking of date palm juice.
The 2018 annual review of the WHO R&D Blueprint list of priority diseases showed that there is an urgent need for accelerated research and development for the Nipah virus, for which there is no treatment or vaccine available - for either people or animals.
People infected with the Nipah virus initially experience symptoms including fever, headache, muscle aches, vomiting, and sore throat. Dizziness, drowsiness, altered consciousness, and neurological signs that indicate acute encephalitis, can follow.
Some people can also experience atypical pneumonia and severe breathing problems, including acute respiratory distress. In severe cases, seizures can lead to coma within 24-48 hours.
The incubation period, which is the interval from infection to the onset of symptoms, ranges from four to 14 days. At the longest, there are examples of cases of Nipah virus infection with an incubation period of 45 days.
According to the WHO’s disease guidelines on the virus: “In the absence of a vaccine, the only way to reduce or prevent infection in people is by raising awareness of the risk factors and educating people about the measures they can take to reduce exposure to the Nipah virus.”