Dr KK Aggarwal
So far COVID 19 is a “public-health emergency of international concern”
- The WHO defines a pandemic as “the worldwide spread of a new disease.”
- It’s also defined by a lack of available treatment, a lack of human immunity, and an ability to spread from person to person.
- A pandemic disease spreads across “several countries or continents, usually affecting a large number of people,” according to the US Centers for Disease Control and Prevention (CDC).
- Virus outbreaks can be characterized as a pandemic if the disease is “markedly different from recently circulating strains” and if “humans have little or no immunity” to it, according to the UK’s Health and Safety Executive.
- A disease becomes a pandemic when it can infect many humans over a large area, be transferred from person to person, and cause clinical illness.
- The term epidemic, by contrast, refers to a more localized or regional outbreak, rather than a global one. The CDC says an epidemic is an “increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area.” Similarly, the WHO defines an epidemic as the “occurrence in a community or region of cases of an illness, specific health-related behaviour, or other health-related events clearly in excess of normal expectancy.”
The COVID 19 may have originated at the Huanan Seafood Market in Wuhan, Hubei, China. There have been over 1,775 deaths. This virus is transmissible from human to human. The Chinese government has placed Wuhan and the surrounding cities on lockdown. The disease has already spread to 29 countries. However, the World Health Organization (WHO) has not yet declared this a pandemic.
The World Health Organization has a six-stage classification that describes the process by which a novel influenza virus moves from the first few infections in humans through to a pandemic.This starts with the virus mostly infecting animals, with a few cases where animals infect people, then moves through the stage where the virus begins to spread directly between people and ends with a pandemic when infections from the new virus have spread worldwide.
A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For instance, cancer is responsible for many deaths but is not considered a pandemic because the disease is not infectious or contagious.
WHO classification of Influenza Pandemkia:-
Phase 1 no viruses circulating among animals have been reported to cause infections in humans.
In Phase 2 an animal influenza virus circulating among domesticated or wild animals is known to have caused infection in humans, and is therefore considered a potential pandemic threat.
In Phase 3, an animal or human-animal influenza reassortant virus has caused sporadic cases or small clusters of disease in people, but has not resulted in human-to-human transmission sufficient to sustain community-level outbreaks. Limited human-to-human transmission may occur under some circumstances, for example, when there is close contact between an infected person and an unprotected caregiver. However, limited transmission under such restricted circumstances does not indicate that the virus has gained the level of transmissibility among humans necessary to cause a pandemic.
Phase 4 is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to cause “community-level outbreaks.” The ability to cause sustained disease outbreaks in a community marks a significant upwards shift in the risk for a pandemic. Any country that suspects or has verified such an event should urgently consult with WHO so that the situation can be jointly assessed and a decision made by the affected country if implementation of a rapid pandemic containment operation is warranted. Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion.
Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.
Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way.
During the post-peak period, pandemic disease levels in most countries with adequate surveillance will have dropped below peak observed levels. The post-peak period signifies that pandemic activity appears to be decreasing; however, it is uncertain if additional waves will occur and countries will need to be prepared for a second wave.
Previous pandemics have been characterized by waves of activity spread over months. Once the level of disease activity drops, a critical communications task will be to balance this information with the possibility of another wave. Pandemic waves can be separated by months and an immediate “at-ease” signal may be premature.
In the post-pandemic period, influenza disease activity will have returned to levels normally seen for seasonal influenza. It is expected that the pandemic virus will behave as a seasonal influenza A virus. At this stage, it is important to maintain surveillance and update pandemic preparedness and response plans accordingly. An intensive phase of recovery and evaluation may be required.