Attendants wear masks as a precautionary measure against the Nipah virus as they help a patient at the Government Medical College hospital in Kozhikode, in the southern Indian state of Kerala.
CNN  — 

The death toll from the outbreak of Nipah virus has risen to 16 in the southern Indian state of Kerala.

More than 230 people have been tested for the virus, with 18 confirmed by state officials to have contracted it, according to Kerala’s Department of Health and Family Welfare.

All 18 people were hospitalized and quarantined and the last two are currently in recovery.

“The other two are alive and kicking. Their blood is totally clear of the Nipah virus,” said Rajeev Sadanandan, additional chief secretary for the state’s Department of Health and Family Welfare.

The recovering patients are still in quarantine and are able to speak to their family over the phone. A final set of tests is being conducted to ensure there is no trace of infection.

The state is close to declaring that the infection has been cleared, said Sadanandan.

The first cases were reported on May 19 in a family from the district of Kozhikode, after which India’s Ministry of Health and Family Welfare and the World Health Organization were alerted. India’s health ministry promptly deployed a response team.

Fruit bats, which are natural hosts of Nipah virus, were found in an unused well near the family’s house, along with rabbits being bred that had recently died, WHO said.

In the first few days of the outbreak, a local nurse, Lini Puthussery, contracted the virus while taking care of these patients and passed away. The Indian government announced they would compensate her family and others that have lost relatives to the Nipah virus.

The World Health Organization has classified the Nipah virus as a ‘public health threat’ and estimates the fatality rate to be between 40% and 75% depending on the outbreak. The rate for the current outbreak is higher, at almost 90%.

State officials have prepared a contact list, extending to 2300 people, who may have come in contact with the infection through multiple degrees of association.

“It is a very dynamic thing. We have been trying to contain this from day one. The district administration is working very hard as a team,” said UV Jose, a district official in Kozikhode,

The last new infection was reported on May 18 and the incubation period of the virus is 21 days, said Sadanandan.

Pragmatically speaking, we are assuming that there is no more infection, said Sadanandan.

“However, the last person who died was on May 29 and we will take 42 days from then before declaring that the infection is closed once and for all,” he added.

According to WHO between four and 14 days may elapse between the infection and a patient’s first symptoms, but that a 45-day incubation period has been reported.

The state-wide alert has not been withdrawn yet. Officials are hoping it will be withdrawn by the end of the week.

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    Initial symptoms of Nipah virus can include headaches and drowsiness, and patients can slip into a coma within days, according to the US Centers for Disease Control and Prevention. Other symptoms may include acute respiratory syndrome – in which the lungs cannot get enough oxygen to the body – and fatal encephalitis, an inflammation of the brain.

    The virus was first identified during a 1998-1999 outbreak in Malaysia, where almost 300 people were infected and more than 100 died, according to the CDC. More than 1 million pigs were euthanized to halt the spread of the illness.

    The virus was named after the village of Kampung Sungai Nipah, where pig farmers contracted the disease.

    Only a few outbreaks have happened since then, including in India and Bangladesh, according to the WHO.

    CNN’s Meera Senthilingam and Susan Scutti contributed to this report.