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Paris, Apr 17: Even as virologists zero in on the virus that causes COVID-19, a very basic question remains unanswered: do those who recover from the disease have immunity?

There is no clear answer to this question, experts say, even if many have assumed that contracting the potentially deadly disease confers immunity, at least for a while.

"Being immunised means that you have developed an immune response against a virus such that you can repulse it," explained Eric Vivier, a professor of immunology in the public hospital system in Marseilles.

"Our immune systems remember, which normally prevents you from being infected by the same virus later on."

For some viral diseases such a measles, overcoming the sickness confers immunity for life.

But for RNA-based viruses such as Sars-Cov-2 -- the scientific name for the bug that causes the COVID-19 disease -- it takes about three weeks to build up a sufficient quantity of antibodies, and even then they may provide protection for only a few months, Vivier told AFP.

At least that is the theory. In reality, the new coronavirus has thrown up one surprise after another, to the point where virologists and epidemiologists are sure of very little.

"We do not have the answers to that -- it's an unknown," Michael Ryan, executive director of the World Health Organization's Emergencies Programme said in a press conference this week when asked how long a recovered COVID-19 patient would have immunity.

"We would expect that to be a reasonable period of protection, but it is very difficult to say with a new virus -- we can only extrapolate from other coronaviruses, and even that data is quite limited."

For SARS, which killed about 800 people across the world in 2002 and 2003, recovered patients remained protected "for about three years, on average," Francois Balloux director of the Genetics Institute at University College London, said.

"One can certainly get reinfected, but after how much time? We'll only know retroactively."

A recent study from China that has not gone through peer review reported on rhesus monkeys that recovered from Sars-Cov-2 and did not get reinfected when exposed once again to the virus.

"But that doesn't really reveal anything," said Pasteur Institute researcher Frederic Tangy, noting that the experiment unfolded over only a month.

Indeed,several cases from South Korea -- one of the first countries hit by the new coronavirus -- found that patients who recovered from COVID-19 later tested positive for the virus.

But there are several ways to explain that outcome, scientists cautioned.

While it is not impossible that these individuals became infected a second time, there is little evidence this is what happened.

More likely, said Balloux, is that the virus never completely disappeared in the first place and remains -- dormant and asymptomatic -- as a "chronic infection", like herpes.

As tests for live virus and antibodies have not yet been perfected, it is also possible that these patients at some point tested "false negative" when in fact they had not rid themselves of the pathogen.

"That suggests that people remain infected for a long time -- several weeks," Balloux added. "That is not ideal."

Another pre-publication study that looked at 175 recovered patients in Shanghai showed different concentrations of protective antibodies 10 to 15 days after the onset of symptoms.

"But whether that antibody response actually means immunity is a separate question," commented Maria Van Kerhove, Technical Lead of the WHO Emergencies Programme.

"That's something we really need to better understand -- what does that antibody response look like in terms of immunity."

Indeed, a host of questions remain.

"We are at the stage of asking whether someone who has overcome COVID-19 is really that protected," said Jean-Francois Delfraissy, president of France's official science advisory board.

For Tangy, an even grimmer reality cannot be excluded.

"It is possible that the antibodies that someone develops against the virus could actually increase the risk of the disease becoming worse," he said, noting that the most serious symptoms come later, after the patient had formed antibodies.

For the moment, it is also unclear whose antibodies are more potent in beating back the disease: someone who nearly died, or someone with only light symptoms or even no symptoms at all. And does age make a difference?

Faced with all these uncertainties, some experts have doubts about the wisdom of persuing a "herd immunity" strategy such that the virus -- unable to find new victims -- peters out by itself when a majority of the population is immune.

"The only real solution for now is a vaccine," Archie Clements, a professor at Curtin University in Perth Australia, told AFP.

At the same time, laboratories are developing a slew of antibody tests to see what proportion of the population in different countries and regions have been contaminated.

Such an approach has been favoured in Britain and Finland, while in Germany some experts have floated the idea of an "immunity passport" that would allow people to go back to work.

"It's too premature at this point," said Saad Omer, a professor of infectious diseases at the Yale School of Medicine.

"We should be able to get clearer data very quickly -- in a couple of months -- when there will be reliable antibody tests with sensitivity and specificity."

One concern is "false positives" caused by the tests detecting antibodies unrelated to COVID-19.

The idea of immunity passports or certificates also raises ethical questions, researchers say.

"People who absolutely need to work -- to feed their families, for example -- could try to get infected," Balloux.

Kochi, May 22: During the nationwide COVID-19 lockdown, Kerala recorded the highest number of cyber attacks followed by Punjab and Tamil Nadu, a study by anti-virus software firm K7 Computing said on Thursday.

In a statement issued in Chennai, the company said its K7 Computing's Cyber Threat Report, a comprehensive analysis of cyber attacks during the lockdown has found that Kerala recorded the highest number of cyber attacks during this period. The report analyses various cyber attacks within India during the pandemic and reveals that threat actors targeted the state with COVID-themed attacks aimed at exploiting user trust.

In Kerala, regions like Kottayam, Kannur, Kollam, and Kochi saw the highest hits with 462, 374, 236, and 147 attacks respectively, while the state as a whole saw around 2,000 attacks during the period - the highest thus far in the country.

This was followed by Punjab with 207 attacks and Tamil Nadu with 184 attacks, the company said.

The sudden surge in the frequency of attacks witnessed from February 2020 to mid-April 2020 indicates that scamsters across the world were exploiting the widespread panic around coronavirus at both the individual and corporate level.

These attacks aimed to compromise computers and mobile devices to gain access to users' confidential data, banking details, and cryptocurrency accounts.

The key threats seen during this period ranged from phishing attacks to rogue apps disguised as COVID-19 information apps that targeted users' sensitive data. Phishing attacks were noticed more in Tier-II and Tier-III cities while the metros fared better. Smaller cities saw over 250 attacks being blocked per 10,000 users.

Users from Ghaziabad and Lucknow seem to have faced almost 6 and 4 times the number of attacks as Bengaluru users.

According to the statement, a majority of the recorded attacks were phishing attacks with sophisticated campaigns that could easily snare even the most educated users. These attacks were aimed at heightening users' fears and creating a sense of urgency to take action.

K7 Labs noticed phishing attacks where scamsters posed as representatives of the United States Department of Treasury, the World Health Organization (WHO), and the Centres for Disease Control and Prevention (CDC), the company said.

Users were encouraged to visit links that would automatically download malware on the host computer such as the Agent Tesla keylogger or Lokibot information-stealing malware, infamous banking Trojans such as Trickbot or Zeus Sphinx, and even disastrous ransomware.

Other attacks included infected COVID-19 Android apps like CoronaSafetyMask that scam users with promises of masks for an upfront payment; the spyware app Project Spy; and seemingly genuine apps that are infected with dangerous malware like banking Trojans such as Ginp, Anubis and Cerberus.

"Covid-19 has created an ideal situation for various threat actors to target individuals and enterprises alike. The panic caused by the stringent lockdown measures and rapid spread of this virus has left many people looking for more information on the situation," J. Kesavardhanan, Founder and CEO of K7 Computing was quoted as saying in the statement.

"Threat actors exploit this fear to their advantage and scam users into downloading malicious software and divulging sensitive information like banking codes. The need to be cyber cautious has never been greater. This is more so in the case of corporates who have adopted a work from home policy hurriedly without adequate cyber hygiene. We have seen an increase in attacks on enterprises and SME employees as well," he added.

Such attacks are expected to continue till normalcy returns. Social engineering attacks targeted at winning users' trust will gain momentum.

Healthcare institutions, well-known government offices, and international organisations will continue to be a prime target throughout the pandemic, the statement said.

Tokyo, Feb 25: Japan's Chitetsu Watanabe, recognized at 112 years as the oldest man in the world, has passed away 11 days after he received the Guinness World Record certificate, his family said on Tuesday.

Watanabe died on Sunday night, Efe news reported.

He received the official certificate on February 12 at a nursing home in Joetsu in Niigata prefecture, where he resided.

Soon after being certified as the oldest man, he began to experience a lack of appetite and respiratory problems, the wife of his eldest son told public broadcaster NHK.

Born on March 5, 1907 in a family of farmers, Watanabe moved at the age of 20 to Taiwan, where he worked at a sugar refinery for 18 years before returning to Japan after the end of World War II.

A fan of calligraphy, custard and ice cream, Watanabe told the Guinness team that the key to his long life was laughter.

He was recognized as the oldest male in the world following the deaths in 2019 of German Gustav Gerneth (in October), aged 114 years, and Japan's Masazo Nonaka (in January), at the age of 113, three months older than the German.

It remains to be seen who will be recognized after the death of Watanabe, the only male on the list drawn up by the Gerontology Research Group of the 30 oldest people in the world.

Japan has among the highest life expectancy in the world and the number of centenarians in the country has crossed 71,000, according to the latest government figures.

Since 2000, the number of centenarians censored has quintupled, raising concern for the economic outlook and future workforce of the country - where the birthrate is on a downward trend.

Out of these, 88 per cent are women.