Omicron: The Fast spreading Virus
Dr. Umer Farooq M.D
Omicron virus has rung the bell of alarm in the Union Territory of Jammu & Kashmir. The three cases detected in Jammu have to be examined in reverse direction also. The three women detected positive for the virus have no travel history and apparently have no contact with any such known patients.
The main question now is how they got infected with a virus not yet known in the UT? Can we say that the virus is already in the community and is spreading untraced? The samples of these patients were taken on 30th November and 8th December and sent to NCDC New Delhi for genome sequencing. Their positive reports were received on 21st December.
The good news about these ladies is that have now already tested negative for the virus. As they had tested previously positive for Covid-19, it is expected that they might have been put under home quarantine. Had it not be so, then the workload of the medical teams is enormous as to trace their contacts, test them and send a few samples for genome sequencing.
Much has been written about the new omicron variant but like early variants of the virus the findings are likely to change with every passing day. Till date what we know about the omicron is that it spreads fast than the Delta variant that killed lakhs of patients in the world and has left all including the scientists wonder struck about its speed of spread and mortality.
World Health Organization in its recent briefings has confirmed that the Omicron variant of the corona virus is spreading faster than the Delta variant and is causing infections in people already vaccinated or who have recovered from the COVID-19 disease. WHO scientists have also said thatit would be “unwise” to conclude from early evidence that Omicron was a milder variant than that of previous ones.
What is Omicron?
It is a new variant of SARS-CoV-2 that has been reported from South Africa on 24th November 2021 called as B.1.1.529 or Omicron. This variant has shown a very large number of mutations, especially more than 30 on the viral spike protein, which is the key target of the immune response.
How to detect Omicron?
The most accepted and commonly used method of diagnostic for SARS-CoV2 Variant is RT-PCR method. This method detects specific genes in the virus, such as Spike (S), Enveloped (E) and Nucleocapsid (N) etc to confirm the presence of virus. However, in case of Omicron, as the S gene is heavily mutated, some of the primers may lead to results indicating absence of the S gene (called as S gene drop out). This particular S gene drop out along with the detection of other viral genes could be used a diagnostic feature of Omicron. However, for final confirmation of the omicron variant genomic sequencing is required.
How fast it spreads?
Omicron virus spreads faster than its previous cousins. It was reported that the Delta variant of the corona virus was multiplying in 5 days whereas Omicron variants multiply in 1.5 to 3 days.
The Omicron variant of coronavirus has been reported in 89 countries and the number of cases is doubling in 1.5 to 3 days in areas with community transmission, said WHO.
Scientists are concerned about the findings that Omicron is spreading rapidly in countries with high levels of population immunity. The variant has spread in European countries with high level of population immunity more rapidly and forcing all the affected countries to put stringent restrictions.
It is important to highlight that Omicron has been declared VoC (Variant of Concern) based on the observed mutations, their predicted features of increased transmission and immune evasion, and preliminary evidence of detrimental change in COVID-19 epidemiology, such as increased reinfections.
In a recent research it has been reported that Omicron multiplies faster in airways and slower in lungs which makes it less-severe illness.
“Compared to the earlier Delta variant, Omicron multiplies itself 70 times more quickly in tissues that line airway passages, which may facilitate person-to-person spread, they said. But in lung tissues, Omicron replicates 10 times more slowly than the original version of the coronavirus, which might contribute to less-severe illness”.
In a news release issued by Hong Kong University, study leader Dr. Michael Chan Chi-wai said, “It is important to note that the severity of disease in humans is not determined only by virus replication” but also by each person’s immune response to the infection, which sometimes evolves into life-threatening inflammation.
Chan added, “By infecting many more people, a very infectious virus may cause more severe disease and death even though the virus itself may be less pathogenic. Therefore, taken together with our recent studies showing that the Omicron variant can partially escape immunity from vaccines and past infection, the overall threat from Omicron variant is likely to be very significant.”
A formal report of the findings is under peer review for publication and has not been released by the research team.
How effective are COVID-19 vaccines against omicron?
First of all let us see what vaccines do. A vaccine activates the immune system to produce antibodies that remain in your body to fight against exposure to a virus in the future.
All new vaccines must undergo clinical trials in which researchers test the vaccines on thousands of people to examine how well they work and whether they are safe.
What does the efficacy of a vaccine mean?
Efficacy is the measure of how well a vaccine works in clinical trials. Researchers design the trials to include two groups of people: those who receive the vaccine and those who receive a placebo. They calculate the vaccine’s efficacy by comparing how many cases of the illness occur in each group, vaccinated versus placebo.
What does the effectiveness of a vaccine mean?
Effectiveness, on the other hand, describes how well a vaccine performs in the real world. It is calculated the same way, by comparing illness among vaccinated and unvaccinated people.
Efficacy and effectiveness are usually close to each other but won’t necessarily be the same. How the vaccines work will vary a bit from the trial results once millions of people are getting vaccinated.
Many factors influence how a vaccine performs in the real world. New variants like delta and omicron may change things. The number and age of people enrolled in the trials matter. And the health of those receiving the vaccine is also important.
The proportion of a population that gets vaccinated – can also influence vaccine effectiveness. When a large enough proportion of the population is vaccinated, herd immunity begins to come into play. Vaccines with moderate or even low efficacy can work very well at a population level. Likewise, vaccines with high efficacy in clinical trials, like coronavirus vaccines, may have lower effectiveness and a small impact if there isn’t high vaccine uptake in the population.
Are Covid-19 vaccines effective for Omicron variant also?
The preliminary data about omicron and vaccines is coming in quickly and is revealing lower vaccine effectiveness. Best estimates suggest vaccines are around 30%-40% effective at preventing infections but 70% effective at preventing severe disease.
However, vaccine protection is also by antibodies as well as by cellular immunity, which is expected to be relatively better preserved. Hence vaccines are expected to still offer protection against severe disease and, vaccination with the available vaccines is crucial.
What precautions one should take?
The precautions and steps to be taken remain same as before. It is essential to mask properly, maintain social distancing and maintain good ventilation to the maximum possible and take both doses of vaccines (if not yet vaccinated and if eligible)
Cases have surfaced in Tamil Nadu, Karnataka, Maharashtra, and Delhi where source of infection has not been traced which raises fears of community spread. In J&K also the cases detected had no apparent source of Omicron infection. There may be many more cases than just few that have been confirmed. We need to shift our focus from a target testing to community testing, especially in those areas where some cases have been detected, as that would determine the actual extant of community transmission and would allow the local authorities to implement containment strategies. New Genome sequence facilities need to be established as soon as possible to detect this new varient at the earliest and contain its spread.
(The author is Assistant Professor, Community Medicine Muzaffarnagar Medical College Utter Pradesh)