Earlier this week, in Nipah Transmission In Kerala Outbreak, we looked at the apparently robust household and nosocomial transmission of the Nipah virus from an index case to 17 others (and 1 secondary nosocomial transmission).
This outbreak, in a highly populated region of Southern India, was fortunately stopped at 19 cases, and declared over on July 1st.But it occurred in an area more than 1000 miles removed from India's two previous outbreaks (West Bengal in 2007 & 2001), and serves as a reminder that exotic viral diseases can turn up in places where you don't normally expect them.
Last March, the WHO List Of Blueprint Priority Diseases, published a short list of 8 disease threats in need of urgent accelerated research and development. Nipah, and its Australian cousin Hendra, was among them.
Three weeks ago, in IJID: Enhancing Preparation For Large Nipah Outbreaks Beyond Bangladesh, we looked at a new open-access article that appeared in the International Journal of Infectious Diseases, that discussed the potential of the Nipah virus producing a large urban epidemic, similar to what we saw in West Africa with Ebola in 2014.
Today we've an unusually detailed narrative of India's recent brush with Nipah, published as an editorial in the Indian Journal of Critical Care Medicine.One that not only describes the patients, their treatment, and their outcomes - but also delves into the myriad challenges of dealing with an (initially) unidentified infectious pathogen in a densely populated region - including contact tracing and quarantine.
Other challenges involved getting cooperation and permission from relatives to do an autopsy on the index case, and dealing with the loss of a nurse who treated the index case and later succumbed to the virus.
I'll only post the link, and the opening few sentences, but will urge you to read the editorial in its entirety. When you return, I'll have more.
Deadly Nipah outbreak in Kerala: Lessons learned for the future
AK Ajith Kumar1, AS Anoop Kumar2
The recent reemergence of Nipah virus belonging to the family Paramyxoviridae caused 17 case fatalities among the 19 infected patients (89% mortality) in Kozhikode (Calicut), a city in the state of Kerala, South India.
It is extremely sad to note that Mrs. Lini Puthussery, a very committed young nurse who looked after the index patient, had to sacrifice her own life to the deadly illness.
The outbreak has drawn immense global attention and underlines the need for adequate preparedness in the event of such episodes resurging in the future.
(Continue . . . )
Ajith Kumar A K, Anoop Kumar A S. Deadly Nipah outbreak in Kerala: Lessons learned for the future. Indian J Crit Care Med [serial online] 2018 [cited 2018 Jul 21];22:475-6.
Available from: http://www.ijccm.org/text.asp?2018/22/7/475/236914
Nearly two decades after it was first identified among hundreds of abattoir workers exposed to infected pigs (see MMWR Update: Outbreak of Nipah Virus -- Malaysia and Singapore, 1999), our understanding of exactly how the Nipah virus transmits in the human population remains limited.
The CDC's briefly (and somewhat vaguely) states:
Transmission of Nipah virus to humans may occur after direct contact with infected bats, infected pigs, or from other NiV infected people.
In Malaysia and Singapore, humans were apparently infected with Nipah virus only through close contact with infected pigs. The NiV strain identified in this outbreak appeared to have been transmitted initially from bats to pigs, with subsequent spread within pig populations. Incidental human infections resulted after exposure to infected pigs. No occurrence of person-to-person transmission was reported in this outbreak.
Conversely, person-to-person transmission of Nipah virus in Bangladesh and India is regularly reported. This is most commonly seen in the family and caregivers of Nipah virus-infected patients.
Transmission also occurs from direct exposure to infected bats. A common example is consumption of raw date palm sap contaminated with infectious bat excretions.(Continue . . . )
Although not believed to be `airborne' in the traditional sense - the Nipah virus is readily detected in the saliva and respiratory secretions of infected patients - and can probably be spread via large droplets propelled by violent coughing.
From a 2009 paper (Transmission of Human Infection with Nipah Virus by published in Clinical Infectious Diseases, we get the following description of the transmission of the Nipah virus across 5 generations.
The clearest illustration of person-to-person NiV transmission occurred during the Faridpur outbreak in 2004 . Four persons who cared for the index patient—his mother, his son, his aunt, and a neighbor—became ill 15–27 days after the index patient first developed illness (Figure 2).
During her hospitalization, the index patient's aunt was cared for by a popular religious leader who lived in a nearby village and who became ill 13 days later.
When the religious leader became seriously ill, many of his relatives and members of his religious community visited at his home. Twenty-two persons developed Nipah infection after contact with the religious leader.
One of these followers moved to his family's house in an adjacent village to receive care after becoming ill where he was cared for by a friend and 2 family members. These 3 caregivers and a rickshaw driver, who helped carry him to the hospital as his condition deteriorated, became ill.
Ultimately, the chain of transmission involved 5 generations and affected 34 people  (Figure 2). Physical contact with an NiV-infected patient who later died (OR, 13.4; 95% CI, 2.0–89) was the strongest risk factor for developing NiV infection in the outbreak
This article goes on to list a number of unanswered questions regarding the Nipah virus, including:
(1) Why is respiratory disease and person-to-person transmission more common among human NiV infection in Bangladesh compared to Malaysia?
Are certain strains of virus more likely to cause respiratory tract disease in humans, or might the different clinical syndromes in Bangladesh and Malaysia reflect differences in host susceptibility from malnutrition or other causes?
(2) How stable is the genome of Nipah?
The overall nucleotide homology between a prototypical Malaysian strain of NiV and a strain of NiV from Bangladesh was 91.8% .
Is there a substantial risk of mutation that would improve the efficiency of person-to-person transmission of the virus?
(3) How common is unrecognized, including subclinical, infection with NiV?
All good questions, that nearly a decade later, still await definitive answers.