Forty years ago it seemed as if infectious diseases were on the verge of becoming extinct. Polio and smallpox had all but been eradicated. Our arsenal of miracle drugs were still potent against nearly all of the bacterial invaders.
In 1969, the Surgeon General of the United States, William H. Stewart, declared, "The war against diseases has been won."
In the 3rd edition of the textbook Natural History of Infectious Disease, published in 1962, the forward declared that the late 20th century would be witness to "the virtual elimination of infectious disease as a significant factor in social life."
Science, we believed, has liberated us from the threats of infectious diseases.
It wasn't true, of course. There were still plenty of infectious diseases in the world, running unchecked. But our potential to eradicate them appeared real enough, and given enough time and resources, it seemed within our grasp.
But something unexpected happened, although in retrospect, we should have seen it coming.
Nature compensated for our modern science and our miracle drugs, sending us antibiotic resistant bacteria, and new viral pathogens to deal with. Even old enemies, once believed nearly vanquished, began showing up again- sometimes learning new tricks. Polio, Tuberculosis, Yellow Fever, and even Measles are seeing comebacks.
Over the past 35 years more than 30 new zoonotic diseases have emerged; diseases once found only in animals, but that have now jumped the species barrier to man.
These emerging infectious diseases, often springing forth from equatorial regions of the earth, are the new frontier in our battle against communicable diseases.
The H5N1 bird flu virus is one of these zoonotic diseases, and one that worries us greatly because of influenza's known history of spreading far and wide. But there are others with, if not pandemic potential, at least the ability to spark epidemics.
One of the most interesting of these newly emerging infectious diseases is the Nipah Virus, which is now being reported again in Bangladesh after a 3 year absence.
Unknown until 1998, this virus appears to be carried by certain species of fruit bats that are distributed across portions of of Australia, Indonesia, Malaysia, and the Philippines islands. While the bats are the natural host for this virus (along with another variant called the Hendra Virus), they are unaffected by it.
The bats are believed to transmit the virus, via their saliva or other fluids, to pigs (Nipah) or horses (Hendra). From there, the virus has found its way into the human population.
The Nipah virus was first detected in Malaysia in 1998, where it infected 250 people and claimed 100 lives. The most common vector appeared to be from pigs to humans. Over 1 million pigs were culled in Malaysia to control that outbreak.
While human-to-human transmission has not been demonstrated, the outbreak in Bangladesh in 2004 included victims that had no known contact to pigs or infected animals. Because of this, Human-to-human transmission hasn't been ruled out.
From the CDC's Journal of Emerging Infectious Diseases, December 2004 issue, Hsu VP, Hossain MJ, Parashar UD, Ali MM, Ksiazek TG, Kuzmin I, et al. Nipah virus encephalitis reemergence, Bangladesh.
Human-to-human transmission of Nipah virus was not shown in the Malaysia and Singapore outbreaks (7), but several findings from the Bangladesh outbreaks suggest that close contact may have resulted in transmission.
In Meherpur and in Naogaon, clusters of cases occurred within family households, with dates of symptom onset occurring over a range of time. In Meherpur, relatives with close contact with patients became ill, and handling or exposure to secretions of patients was found to be a risk factor for illness.
Nipah virus has been detected in respiratory secretions and urine of patients, which suggests that person-to-person transmission is possible (14). However, we cannot rule out the possibility that a common source within households and among relatives may have been responsible for infection.
While the Nipah Virus may not pose as great of a threat to the world as a pandemic influenza, it does point out the need for increased surveillance and improved public health programs around the world. If we ignore these diseases, we do so at our peril, for once they establish themselves, they can quickly spread out of control.
And the next zoonotic disease to emerge may be a lot harder to contain than the Nipah virus.
Organizations like the WHO, the CDC, the FAO, and OIE are our first line of defense against these newly emerging infectious diseases. With the increase in world travel over the past few decades, we haven't the luxury of ignoring what happens in Bangladesh or Malaysia anymore.
The Nipah virus is a not-so-gentle reminder that we live in a world awash in viral pathogens, and that we must remain ever vigilant.
Unlike man, nature never rests.
Monday, 03 March 2008
Nipah virus claimed two more lives on Saturday, raising the death toll to six since its fresh outbreak was reported last week in Manikganj and Rajbari districts.
Rabiul Mullah, 9 and Neyamat Sheikh, 55 died at Rajbari Sadar Hospital on Saturday. Earlier, Shakil Mullah, 11 died on Thursday in Rajbari, while Yusuf, 7, Azahar, 9 and Joshna Akhter Joshi, 11— three children of a family— died in Manikganj.
The Institute of Epidemiology Diseases Control and Research on Saturday confirmed that all the six deaths were caused by nipah virus, which staged a comeback after a gap of three years and was now concentrated on two districts.
Three nipah inflicted persons were cured while two others were undergoing treatment at Rajbari Sadar Hospital, the institute said in a press release.
Biochemical test carried out in IEDCR laboratory detected nipah virus, which causes encephalitis and spreads to humans mainly by fruit bats. Virologists said the virus causes fatal inflammation of the brain, associated with high fever often leading to unconsciousness.
They advised people in the nipah-prevalent areas not to eat fruits bitten or half-bitten by fruit bats, or drink raw juices of palm and date trees.
They also suggested that date juice should not be collected in open pitchers. Two teams from IEDCR have been working in the nipah-affected areas.
A team comprising medical officers Sharmin Sultana and Nusrat Humaira was sent to Rajbari. The institute’s senior scientific officer Saima Afroz is leading another team in Manikganj.