摘要：As cases continue to soar, what does the country need to do to curb the epidemic, how long will the current wave last, and which other countries are at risk of a similar situation?

WHILE life in some rich countries begins to return to a semblance of normality, the global coronavirus crisis is far from over. Official case numbers in India have surpassed 20 million and, globally, the week beginning 26 April was the worst since the pandemic began. Worldwide, the number of reported new daily infections hovers around 900,000, although this is a huge underestimate. More than a third of these are in India, where infections are still rising. New Scientist looks at what happens next.

How much worse will it get for India?

India’s second wave looks set to get a lot worse before it gets better. In terms of the number of people being infected, the outbreak is already by far the worst in the world. Having recorded more than 400,000 cases on 30 April, as New Scientist went to press, reported daily cases were hovering around 350,000 and some models have predicted this could pass half a million in May.

Most models suggest that we will see increases in cases until the middle of May and then we will see a decline, says Gautam Menon at Ashoka University in Sonepat, India.

357,316

Recorded covid-19 cases in India on 3 May

If so, the number of deaths could keep increasing until the end of May. With hospitals already overwhelmed, this would have further devastating consequences.

The US still holds the record for the highest reported daily covid-19 deaths, 4500 on 12 January, and the most reported deaths overall –nearly 600,000. Brazil is second, with 4249 deaths on 8 April and around 400,000 in total.

On 3 May, India reported 3449 new deaths and, so far, it has reported just over 200,000 deaths since the pandemic began. The official figures are thought to greatly underestimate the true number of cases and deaths, however.

In fact, the actual number of daily infections in India could be more than 14 million, according to Christopher Murray at the Institute for Health Metrics and Evaluation (IHME) in Seattle. “The number of infections right now is extraordinarily large,” Murray wrote in an IHME analysis on 23 April. “There are more infections happening in India than what occurred globally two weeks ago.”

“There are more infections happening in India than occurred globally two weeks ago”

According to the IHME, the actual number of daily deaths in India is around 8000 and could peak at 13,000 in May, with the total surpassing 900,000 by the end of June.

Other estimates of the death counts are even worse. John Burn-Murdoch at the Financial Times has compared local news reports to official numbers and concluded that the actual number is at least 10 times higher.

How does India get out of this crisis?

“The key thing is to lock down the country and stop transmission,” says Ravi Gupta at the University of Cambridge.

That is what India did in response to its first wave, imposing a strict country-wide lockdown on 24 March 2020. But the government has been reluctant to impose another lockdown or take other measures. When cases started rising in February, it did nothing, allowing political rallies and religious festivals to continue.

14 million

Suspected number of peak daily covid-19 cases in India

But the issue is complicated. The government gave only 4 hours’ notice before the lockdown and many migrant workers were unable to work and afford food or rent. Lots of people are leaving big cities in fear of the same thing happening again, which could be contributing to the spread of the virus in rural regions

Some cities and regions have imposed restrictions. “There is currently a patchwork of local lockdowns, including in the cities and states which have seen recent sharp increases,” says Menon. “This should certainly help in breaking the chain of transmission in those locations.”

Vaccination is unlikely to help much in the next few weeks. Less than 10 per cent of the 1.4 billion people in India have had at least one dose of a covid-19 vaccine, and it will take many months to get a large proportion of the population vaccinated.

In March, India restricted the export of locally made vaccines. Even if this ban is maintained, science analytics company Airfinity estimates that it would take until November to vaccinate all adults. All over-60s could be vaccinated by the end of May, however, which wouldn’t stop transmission, but should help reduce the number of deaths.

According to the IHME, this second wave might already have peaked in terms of the number of cases. So many people have already been infected that the virus may start to run out of hosts.

“It could take until November to vaccinate all adults in India, and the end of May for the over-60s”

“It could happen,” says Gupta, who thinks the IHME numbers are plausible. But the sheer number of cases suggests that some people infected during the first wave might be being reinfected, he says. “That worries me because it tells me that the things we were worrying about – escape by these viruses – might actually be happening,” he says, referring to the potential of some variants to evade the body’s immune response. “But we don’t know yet.”

How long will this wave last?

Nobody knows for sure, but it is likely to be several months before this second wave is over.

India’s first wave was protracted, beginning in March 2020, peaking in September and gradually declining until February. At its height, India was reporting just under 100,000 new cases and around 1200 deaths per day.

Because this second wave has been allowed to rip through the population in a much less controlled way, case numbers could also come down much more quickly.

“It is hard to say at the moment, but the likelihood is that it will not be too protracted,” says Menon.

Even so, it will take a while. According to the IHME model, the real number of infections will fall from 14 million per day now to 3 million a day by the beginning of June.

The number of deaths, however, will keep increasing until mid-May and won’t fall below the current level until early June. What actually happens, of course, depends largely on what actions are taken in India.

Could other countries see cases soar in a similar way?

That partly depends on the reasons for why India is experiencing such devastating case numbers, which aren’t yet clear. Many scientists have suggested that new variants of the virus that are more infectious or deadly are to blame. In the north of India, the B.1.1.7 variant that originated in the UK is rampaging. Elsewhere, the new B.1.617 variant, which the media have incorrectly termed the “double mutant”, has become common (see “What is India’s “double mutant”,).

Both variants seem to be more transmissible, although it isn’t clear how responsible they are for the change in India’s fortunes, says Gupta.

India’s relaxation of social distancing measures over the past few months is also partly to blame. Politicians, including the prime minister, Narendra Modi, said earlier this year the virus had been defeated, and encouraged mass gatherings. There have also been protests by farmers near Delhi, which has been badly hit in the second wave.

“You can’t use the new [variants] as an excuse for not controlling an epidemic,” says Gupta. “It is because of lax measures, lack of surveillance and then very slow intervention.”

15

The number of mutations in India’s “double mutant” variant

Even events that are held outside can spread the virus when people eat indoors or use public transport, says Michael Head at the University of Southampton, UK. “It was a perfect storm of many large gatherings [without social distancing precautions], in part because political leaders were saying it’s fine to do these things,” he says. “If you give people the perception the pandemic is over, that’s how they will respond.”

As a result, any country where social distancing restrictions ease and vaccination levels are low could experience a similar surge, says Head.

Alongside vaccination numbers, we need to look at what is called the test positivity rate – the share of tests coming back positive – to identify countries at particularly high risk.

“It was a perfect storm of many large gatherings and politicians saying it’s fine to do these things”

Testing helps health services monitor and control the spread of infection, but many people who are infected don’t get tested. They may have no symptoms, they may not wish to self-isolate or there may not be enough tests available. A high test positivity rate suggests there are many people infected who are going undiagnosed and so further spreading the virus.

If a region has a test positivity rate of less than 5 per cent, that is an indicator that its epidemic is under control, according to the World Health Organization.

The UK’s test positivity rate is currently less than 1 per cent, while India’s is about 20 per cent. Other large countries with high test positivity rates and few people vaccinated include Mexico, Argentina and Turkey, says Head. “There could easily be a next India just around the corner,” he says.