Editorial

COVID-19 in pandemic alert period phase 5-6

So far COVID-19 is a "public-health emergency of international concern."

The World Health Organization (WHO) definition of a pandemic as "the worldwide spread of a new disease."

It is also characterized by a lack of available treatment, a lack of human immunity, and ability potential to spread from person to person.

According to the US Centers for Disease Control and Prevention (CDC), a pandemic disease spreads across "several countries or continents, usually affecting a large number of people,".

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, as per the UKs Health and Safety Executive.

A disease is termed a pandemic when it can infect several humans across a large area, can transfer from person to person, and cause clinical illness.

Epidemic, on the other hand, refers to a localized or regional outbreak, rather than on a global level. According to the CDC, 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." 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."

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 WHO has not yet declared this as a pandemic.

The WHO mentions a six-stage classification describing the process by which a novel influenza virus moves from the first few infections in humans through to a pandemic.

It begins with the virus mostly infecting animals, with a few cases of animals infecting people. The classification then moves through the stage where the virus starts spreading directly between people and ends with a pandemic when infections from the new virus have spread globally.

A disease or condition is not termed a pandemic only because it is widespread or kills many people; being infectious is a key criterion. For instance, cancer causes many deaths but is not considered a pandemic because the disease is not infectious.

WHO classification of Influenza Pandemic

Phase 1 no viruses circulating among animals have been reported to lead to infections in humans.

Phase 2 an animal virus circulating among domesticated or wild animals has caused infection in humans, and is considered a potential pandemic threat.

Phase 3 an animal or human-animal influenza reassortant virus has led to sporadic cases or small clusters of disease in people, but has not caused human-to-human transmission sufficient enough to sustain community-level outbreaks. Limited human-to-human transmission may occur under certain circumstances, for instance, close contact between an infected person and an unprotected caregiver. Limited transmission under such restricted circumstances does not indicate that the virus has gained the level of transmissibility among humans necessary to result in a pandemic.

Phase 4 verified human-to-human transmission of an animal or human-animal influenza reassortant virus with the capability of causing “community-level outbreaks.” Thi potential to cause sustained disease outbreaks in a community signifies a significant upwards shift in the risk for a pandemic. Any country suspecting or having verified such an event should consult with WHO in order to facilitate joint assessment and decision-making by the affected country if implementation of a rapid pandemic containment operation is warranted. Phase 4 points to a considerable increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion.

Phase 5 human-to-human spread of the virus into at least two countries in one WHO region. The declaration of Phase 5 strongly points out 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. Community level outbreaks in at least one other country in a different WHO region besides the criteria defined in Phase 5. Declaration of phase 6 indicates that a global pandemic is under way.

Post-peak period - pandemic disease levels in most countries with adequate surveillance will have dropped below peak observed levels. This period signals that the pandemic activity is 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 marked by waves of activity spread across months. Once the level of disease activity declines, a critical communications task will be to balance this information with the possibility of another wave. Pandemic waves can be separated by months and it would be premature to give out an immediate “at-ease” signal.

Post-pandemic period - influenza disease activity will have returned to levels normally seen for seasonal influenza. The pandemic virus will be expected to behave as a seasonal influenza A virus. Maintaining surveillance and updating pandemic preparedness and response plans is key. An intensive phase of recovery and evaluation may be required.

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA