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Thiruvananthapuram, May 22: Domestic flyers arriving in Kerala must undergo strict home quarantine as per the lockdown guidelines, in view of increasing COVID-19 cases in the state, Health Minister K K Shailaja said on Friday.

"Even if the domestic flight services resume, those coming in must remain under strict home quarantine as per the guidelines.

There is no change in that. Most people will be coming from the major hotspots of the country," she said.

Announcing the resumption of domestic flight services from May 25, the Civil Aviation Ministry had indicated on Thursday that it was not in favour of quarantining passengers on short-haul flights.

However, the Assam government has made it mandatory for all air passengers coming to that state to stay in quarantine for 14 days.

Apart from the health department and the local self government institutions, Shailaja said the people of Kerala must also ensure that every returnee to the state remained under strict home quarantine in order to curb the spread of the disease.

"We need to strictly keep under observation all those who come fromoutside the state and make sure that they do not come into contact with others including their family members.

They should be effectively remain under room quarantine at their residence," she said.

The state reported 690 cases after 24 more tested positive for coronavirus on Thursday.

As of now over 80,000 people are under observation across the state.

On the death of a 73-year-old woman, who came from Mumbai, on Thursday, the minister said, "Khadijakuttycame from Mumbai along with three others. She alighted at Chavakkad. Her son who picked her up from there took her to the govt hospital as she was tired. She was given good care."

"However, as her condition worsened, had taken a decision to sent her to the medicalcollege. Her swab test was taken and she was tested positive, but she passed away," Shailaja said.

The minister sounded a word of caution that there would be an increase in cases in the coming days as the influx of people coming from abroad and other states would continue.

"We cannot prevent anyone from coming. They are our brothers and were suffering there. We need to save those who come here and also those who are here," the Minister said.

Shailaja said the southern state had successfully managed the first two phases of the viral outbreak in January and March.

"There were three deaths. But we managed to save the rest of the people including a 93-year-old man," she said.

The Minister further said the situation in the state changed after flight services resumed and the border roads were re-opened after May 7.

"Our fatality rate is low and recovery rate is high.

After May 7, when the flight restrictions were lifted and people from other states started coming in, we reported 188 cases.

At least 90 per cent of the positive cases came from outside and the rest are their contacts," she noted.

The coronavirus can stay aloft for hours in tiny droplets in stagnant air, infecting people as they inhale, mounting scientific evidence suggests.

This risk is highest in crowded indoor spaces with poor ventilation, and may help explain superspreading events reported in meatpacking plants, churches and restaurants.

It’s unclear how often the virus is spread via these tiny droplets, or aerosols, compared with larger droplets that are expelled when a sick person coughs or sneezes, or transmitted through contact with contaminated surfaces, said Linsey Marr, an aerosol expert at Virginia Tech.

Follow latest updates on the Covid-19 pandemic here

Aerosols are released even when a person without symptoms exhales, talks or sings, according to Marr and more than 200 other experts, who have outlined the evidence in an open letter to the World Health Organization.

What is clear, they said, is that people should consider minimizing time indoors with people outside their families. Schools, nursing homes and businesses should consider adding powerful new air filters and ultraviolet lights that can kill airborne viruses.

What does it mean for a virus to be airborne?

For a virus to be airborne means that it can be carried through the air in a viable form. For most pathogens, this is a yes-no scenario. HIV, too delicate to survive outside the body, is not airborne. Measles is airborne, and dangerously so: It can survive in the air for up to two hours.

For the coronavirus, the definition has been more complicated. Experts agree that the virus does not travel long distances or remain viable outdoors. But evidence suggests it can traverse the length of a room and, in one set of experimental conditions, remain viable for perhaps three hours.

How are aerosols different from droplets?

Aerosols are droplets, droplets are aerosols — they do not differ except in size. Scientists sometimes refer to droplets fewer than 5 microns in diameter as aerosols. (By comparison, a red blood cell is about 5 microns in diameter; a human hair is about 50 microns wide.)

From the start of the pandemic, the WHO and other public health organizations have focused on the virus’s ability to spread through large droplets that are expelled when a symptomatic person coughs or sneezes.

These droplets are heavy, relatively speaking, and fall quickly to the floor or onto a surface that others might touch. This is why public health agencies have recommended maintaining a distance of at least 6 feet from others, and frequent hand washing.

But some experts have said for months that infected people also are releasing aerosols when they cough and sneeze. More important, they expel aerosols even when they breathe, talk or sing, especially with some exertion.

Scientists know now that people can spread the virus even in the absence of symptoms — without coughing or sneezing — and aerosols might explain that phenomenon.

Because aerosols are smaller, they contain much less virus than droplets do. But because they are lighter, they can linger in the air for hours, especially in the absence of fresh air. In a crowded indoor space, a single infected person can release enough aerosolized virus over time to infect many people, perhaps seeding a superspreader event.

For droplets to be responsible for that kind of spread, a single person would have to be within a few feet of all the other people, or to have contaminated an object that everyone else touched. All that seems unlikely to many experts: “I have to do too many mental gymnastics to explain those other routes of transmission compared to aerosol transmission, which is much simpler,” Marr said.

Can I stop worrying about physical distancing and washing my hands?

Physical distancing is still very important. The closer you are to an infected person, the more aerosols and droplets you may be exposed to. Washing your hands often is still a good idea.

What’s new is that those two things may not be enough. “We should be placing as much emphasis on masks and ventilation as we do with hand washing,” Marr said. “As far as we can tell, this is equally important, if not more important.”

Should I begin wearing a hospital-grade mask indoors? And how long is too long to stay indoors?

Health care workers may all need to wear N95 masks, which filter out most aerosols. At the moment, they are advised to do so only when engaged in certain medical procedures that are thought to produce aerosols.

For the rest of us, cloth face masks will still greatly reduce risk, as long as most people wear them. At home, when you’re with your own family or with roommates you know to be careful, masks are still not necessary. But it is a good idea to wear them in other indoor spaces, experts said.

As for how long is safe, that is frustratingly tough to answer. A lot depends on whether the room is too crowded to allow for a safe distance from others and whether there is fresh air circulating through the room.

What does airborne transmission mean for reopening schools and colleges?

This is a matter of intense debate. Many schools are poorly ventilated and are too poorly funded to invest in new filtration systems. “There is a huge vulnerability to infection transmission via aerosols in schools,” said Don Milton, an aerosol expert at the University of Maryland.

Most children younger than 12 seem to have only mild symptoms, if any, so elementary schools may get by. “So far, we don’t have evidence that elementary schools will be a problem, but the upper grades, I think, would be more likely to be a problem,” Milton said.

College dorms and classrooms are also cause for concern.

Milton said the government should think of long-term solutions for these problems. Having public schools closed “clogs up the whole economy, and it’s a major vulnerability,” he said.

“Until we understand how this is part of our national defense, and fund it appropriately, we’re going to remain extremely vulnerable to these kinds of biological threats.”

What are some things I can do to minimize the risks?

Do as much as you can outdoors. Despite the many photos of people at beaches, even a somewhat crowded beach, especially on a breezy day, is likely to be safer than a pub or an indoor restaurant with recycled air.

But even outdoors, wear a mask if you are likely to be close to others for an extended period.

When indoors, one simple thing people can do is to “open their windows and doors whenever possible,” Marr said. You can also upgrade the filters in your home air-conditioning systems, or adjust the settings to use more outdoor air rather than recirculated air.

Public buildings and businesses may want to invest in air purifiers and ultraviolet lights that can kill the virus. Despite their reputation, elevators may not be a big risk, Milton said, compared with public bathrooms or offices with stagnant air where you may spend a long time.

If none of those things are possible, try to minimize the time you spend in an indoor space, especially without a mask. The longer you spend inside, the greater the dose of virus you might inhale.

New Delhi, Apr 24: The trajectory of COVID-19 cases could have plateaued and might even fall for some weeks after the lockdown is lifted but India is likely to see a second wave in late July or August with a surge in the number of cases during the monsoon, say scientists.

The timing of the peak will depend on how India is able to control physical distancing and on the level of infection spreads after restrictions are relaxed, they said.

It looks apparent that the trajectory of daily new cases has reached a plateau and eventually it will take a downward fall, maybe for some weeks or even months, Samit Bhattacharya, associate professor at the Department of Mathematics, Shiv Nadar University, said.

Still, we may get a surge of new cases of the same coronavirus and this will be considered a second wave, Bhattacharya explained.

The second epidemic may come back in late July or August in the monsoon, although the peak timing will depend on how we control social distancing during that time, he said.

Rajesh Sundaresan, professor at Bengaluru's Indian Institute of Science (IISc), agreed.

“Once we return to normal activity levels, there is a chance that infection may begin to rise again. China is seeing this to some extent post easing of some restrictions on travel,” Sundaresan, corresponding author of a working paper by researchers at IISc and the Tata Institute of Fundamental Research (TIFR) in Mumbai, said.

On March 25, when the number of coronavirus cases was 618 with 13 deaths, the government announced a nationwide lockdown that was later extended to May 3.

On Friday, the death toll due to COVID-19 rose to 718 and the number of cases to 23,077, according to the Union Health Ministry.

In good news, officials said this week that the doubling rate of cases has slowed down in the period, going from 3.4 days before lockdown to 7.5 days, with 18 states doing better than the national average. The recovery rate has also almost doubled in the last 10 days.

"Looking at the new cases in the past few days, it seems the growth of new daily infection is much slower than earlier. This apparently indicates that we might have reached at the plateau of the growth curve, Bhattacharya said.

He noted that recent studies in China and Europe observed that the infection might relapse in those people who have already recovered from earlier phases.

So, there is no evidence that the earlier infection may help acquire immunity against the second infection. And in that way, the entire population may be vulnerable to the second wave to some extent, said the scientist.

In their study unveiled this week, IISc and TIFR researchers analysed the impact of strategies such as case isolation, home quarantine, social distancing and various post-lockdown restrictions on COVID-19 that might remain in force for some time.

The study modelled on Bengaluru and Mumbai suggests the infection is likely to have a second wave and the public health threat will remain, unless steps are taken to aggressively trace, localise, isolate the cases, and prevent influx of new infections.

The new levels and the peaking times for healthcare demand depend on the levels of infection spreads in each city at the time of relaxation of restrictions, they said.

The lockdown is currently upon us. It has given us valuable time. Let us test, trace, quarantine, isolate, practice better hygiene, search for a vaccine, etc. We should do these anyway, and these are being done. When and how to lift the lockdown is going to be a difficult decision to make, said Sundaresan.

It's clear that it's going to be phased. What our team is focusing on is to come up with tools to help the decision makers assess the public health impact of various choices, he said.

According to the experts, infectious diseases spread via contact between infectious and susceptible people. In the absence of any control measures, an outbreak will grow as long as the average number of people infected by each infectious person is more than one.

Once enough people are immune there will be fewer people susceptible to the infection and the outbreak will die.

However, when an outbreak is brought under control by social distancing and other interventions, it is possible only a small proportion of the population will have been infected and gained immunity, they said.

This means enough susceptible people may remain to fuel a second wave if controls are relaxed and infection is reintroduced.

Until the vaccine comes on the market, we have to remain alert Once sporadic cases occur here and there in the country, we immediately need to implement quarantine or social distancing locally for the people in that region, and also need to perform tests to identify positive cases irrespective of showing symptoms, Bhattacharya explained.

Note that these monsoon months are also flu season in many places of India. So, we should not ignore the early signs of the flu symptoms. Irrespective of symptoms, we need to increase tests in the hotspots to identify people and contain the surge, he said.

Sundaresan added that the timeline for a second wave will depend on a lot of circumstances which may change as the time passes.

Significant testing may have been underway, there may be behavioural changes with people becoming more careful about their hygiene, wearing masks may become more common, etc. All these responses may help restrict the second wave, he said.

A study published in The Lancet journal earlier this month modelled the potential adverse consequences of premature relaxation of interventions, and found it might lead to a second wave of infections.

The finding is critical to governments globally, because it warns against premature relaxation of strict interventions, the researchers said.

While interventions to control the spread of SARS-CoV-2 are in place, countries will need to work toward returning to normalcy; thus, knowledge of the effect of each intervention is urgently required, they said in the study.

According to a recent analysis by the Harvard Chan School of Public Health, the best strategy to ease the critical care burden and loss of life from COVID-19 might be on-again, off-again social distancing.

In the absence of such interventions, surveillance and intermittent distancing may need to be maintained into 2022, which would present a substantial social and economic burden, the researchers wrote.p