There is talk of COVID 4th wave; What exactly is a wave?

Oxford University scholars said the term “wave” came from the 1889-92 flu outbreak, which had distinct phases thought to have occurred over several years

Representative picture.

The number of new COVID cases in India has increased. Because of this, there are fears that a fourth wave is coming. There is also the possibility of mini waves.

According to the World Health Organization (WHO) chief scientist, Dr. Soumya Swaminathan, the test positivity rate and hospital admissions point to another wave in the country.

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“Epidemiological factors such as the test positivity rate and hospital admissions point to another wave. But this wave may not be clearly visible on the graph because the tests are small. Most people are confident that vaccination will protect them from serious diseases,” said Dr. Quoted from Swaminathan Indian times.

She added that miniwaves could occur every four to six months. “The newly emerging subvariants are more easily transmissible than the original Omicron BA.1, and there is a likelihood that immunity will wane. It’s possible that there are miniwaves about every four to six months and so it’s important to track the variant alongside any Covid-appropriate precautions that need to be taken,” said Dr. Swaminathan Indian Express.

what is a wave

According to Marc Lipsitch, director of the Center for Communicable Disease Dynamics at the Harvard School of Public Health, there is no single definition of a wave — it simply refers to a sustained increase in cases.

“A wave is just a metaphor. It’s not a term with a precise definition in epidemiology, but it’s a useful metaphor indicating that whatever the level of daily incidence of new cases, there is an increase,” he said ABC.

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Abram L. Wagner, Assistant Research Professor of Epidemiology, University of Michigan, wrote The conversation that there is no strict definition of what is or is not an epidemic wave or phase. “Disease waves are not scientifically defined,” he said.

“A wave implies an increasing number of sick people, a defined peak and then a decline. The word wave implies a natural pattern of peaks and valleys; it suggests that even during a lull, future outbreaks of the disease are possible,” he said.

“Historical outbreaks of infectious diseases offer some models of how the course of a disease like COVID-19 might evolve over time. Some diseases come in somewhat predictable seasonal waves, with higher transmission rates at some times of the year than others,” he added.

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Tom Jefferson and Carl Heneghan, Oxford University scientists in evidence-based medicine, said the term “wave” came from the 1889-92 flu outbreak, which had distinct phases thought to have occurred over several years. It had three waves.

“Waves, as in the sea, are usually preceded by a trough, but this visual analogy is hardly ever mentioned; nor the adequacy of forecasting waves in a coronavirus pandemic,” they stated.

“Waves imply a lack of viral circulation, which is probably an illusion. It is possible that some of the waves or phases were caused or facilitated by the co-circulation of other microorganisms. Waves are also visible and mostly rhythmic,” they said.

The H1N1 “Spanish flu” pandemic of 1918 is described as having multiple waves. However, said Stephen Morse, PhD, of Columbia University’s Mailman School of Public Health in New York City MedPage today that a wave is a biological phenomenon and it is not clear how to tell if a wave has exited.

“It’s not particularly scientific: how you define a wave is arbitrary,” said Dr. Mike Tildesley from the University of Warwick BBC.

What does the WHO say?

According to the WHO, in order to end a pandemic wave, “the virus must be brought under control and the cases must be reduced significantly. Then you need a sustained spike in infections for a second wave to start.”

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“Previous pandemics have been characterized by waves of activity lasting months. Once disease activity falls, a crucial communication task is to reconcile this information with the possibility of another wave. Pandemic waves can be months apart, and an immediate “signal to calm down” may be premature.

“In the post-pandemic period, influenza disease activity will have returned to levels normally observed for seasonal influenza. The pandemic virus is expected to behave like a seasonal influenza A virus. At this stage, it is important to maintain surveillance and update pandemic preparedness and response plans accordingly. An intense period of recovery and assessment may be required,” WHO added.

What ICMR said

Recently, a leading health expert from the Indian Council of Medical Research (ICMR) ruled out a fourth wave coming to the country.

Samiran Panda, the additional director-general of the ICMR, told ANI: “It is wrong to say that the fourth wave is coming, we have to examine the data at the district level. A high number of cases in a few districts cannot be interpreted as a nationwide uniform increase in cases. Not every variant is a worrying variant.”

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