Q: What is contact tracing and how does it help in stopping the spread of a disease?

Krishna: Contact tracing  which when combined with social distancing, has proven a powerful asset in controlling the spread of COVID-19. It means assigning a “contact tracer” to interview each person with a confirmed case of COVID-19. The contact tracer, through painstaking and quick detective work, finds out who else might have already acquired the virus from the infectious person, or been exposed.

“Close contacts” of a person who might have COVID-19 can then be isolated (if sick) or quarantined (if well) to lessen further spread of the virus. The contact tracer will be especially interested in any contact who may be in a higher-risk group, such as older or immuno-compromised people.

This technique has also been used to better understand and limit the spread of HIV, meningitis and other diseases. It is a powerful tool discovered almost a century ago to limit the spread of sexually transmitted infections in the US.

The COVID-19 virus is located in the respiratory tract and is spread when someone coughs or sneezes, dispersing infected droplets like a scatter gun.

One sneeze or cough can spread infected droplets everywhere, even onto surfaces that people may touch later. 

Several people can be infected from one COVID-19 positive person, even by later entering a room and touching contaminated objects.

So contact tracing under these circumstances is challenging. The droplet spreader will have to recall his or her movements carefully.

The contact tracer will be especially interested to know:

• who has this confirmed case met or talked with recently? Was it inside or outside?
• who have they sat near, for example in a lecture hall or other enclosed space?
• have they been to a big event like a cricket match?

Close contacts are those who have had face-to-face contact with a confirmed case for a period more than 15 minutes, or those who have shared an enclosed space with a confirmed case for more than two hours. We are not looking for people the person may have passed on the street or in a shop, as the risk in these situations is extremely low.

If you have been in close contact with someone who has a confirmed case of novel coronavirus you need to self-quarantine for 14 days from your last contact with them. If you become unwell during that period, see a doctor immediately.

If the contact tracing process was applied to every COVID-19 case, it would help reduce (but not completely stop) the spread of the coronavirus. It’s important to remember that possiblyless than half of all infected people are symptomatic. Contact tracing could help find those people and ask them to self-isolate. In the real world, however, the effectiveness of contact tracing depends on the skills, extent and capacity of the contact tracing workforce as well as compliance with the contact tracers’ advice.

Q: What are retro viruses?

Krishna: Retroviruses (or, more correctly, retroviridae) are a specific type of virus that contain Reverse transcriptase, a special enzyme that can create DNA from RNA.

Living organisms replicate  by using DNA, which contains a “blueprint” for the organism all, in order to create more copies of themselves. Usually within a cell, there is the machinery that can take the double-helix of DNA, pull it apart, transcribe it into RNA, which is used as “instructions” as to what to do (which can be replication, but can also be a whole load of other jobs that cells do, but basically creating different proteins), and put it back together.

Viruses do not contain the machinery to replicate, so they have to enter a cell (i.e., infect it), and then use their DNA or RNA in order to “hijack” the machinery of that cell, and get it to make more of the virus, which can then spread from that cell to new cells, and make more copies of itself.

Some viruses contain an enzyme called reverse transcriptase that can create DNA from RNA. Retroviruses are viruses that have this reverse transcriptase, and can therefore not only hijack a cell in order to create more viruses, but actually become incorporated into the cell, this creating more infected cells, and not just more viruses.

Two examples of retro viruses are The Human Immunodeficiency Virus, the HIV that causes AIDS and  a retrovirus known as human T-cell lymphotropic virus type 1 (HTLV-1) causes a form of cancer called adult T-cell leukemia (ATL).

Q: How are corona virus tests conducted?

Krishna: The first step in any coronavirus test is collecting a sample. Doing so involves placing a sterile swab at the back of a patient’s nasal passage, where it connects to the throat via the nasopharynx, for several seconds to absorb secretions. The swab is thin—less than three millimeters in diameter at its tip. Once you place it in the back of the throat, it’s uncomfortable, but you can still breathe and talk.  After a sample is collected, the swab goes into a liquid-filled tube for transport.

To determine whether a nasopharyngeal sample is positive for the coronavirus, biotechnicians use a technique known as reverse transcriptase polymerase chain reaction, or RT-PCR. The World Health Organization’s and CDC’s test kits both use this method.

First, a technician extracts viral genetic material called RNA—if it is present—from the sample and uses it to produce a complimentary strand of DNA that the RT-PCR technique amplifies, or makes thousands of copies of, to get a measurable result. The primary difference from one kit to another is which coronavirus genes each test targets. CDC- approved kits target regions on a gene that codes for the protein that makes the virus’s nucleocapsid, an envelope that houses its RNA. The biotechnology companies Roche Diagnostics, LabCorp and Thermo Fisher Scientific are among teh top suppliers of commercial coronavirus RT-PCR kits. Most RT-PCR tests take anywhere from a few hours to a few days to process.

The positive predictive value, or likelihood a positive test result correctly reflects that a patient has  COVID-19, depends on how widespread the disease is. there can be false positives or negatives too.

Another approach relies on identifying antibodies to the coronavirus (SARS-CoV-2) in a patient’s bloodstream to determine whether that person previously had COVID-19. This is not a test for [ongoing] infections. It basically looks for antibodies after the fact, after you had an infection. Like other serological, or antibody-based, diagnostic assays, it uses an enzyme-linked immunosorbent assay (ELISA), which employs a portion of the target virus to find antibodies. Although serological tests are not useful for quickly identifying whether a patient currently has COVID-19,  they can help researchers understand how humans produce antibodies to the virus.

Patients with severe cases of COVID-19 may be able to be treated with blood plasma from people who have developed antibodies and are immune to the disease in what is effectively an antibody-transfer operation.

Serological tests can also help determine if a person has been infected whether or not the individual had symptoms—something an RNA test kit cannot do after the fact, because it only looks for the virus itself. That means serological tests could be used to survey a population to determine how widespread infection rates were. It also could allow public health agencies to figure out who is already immune to COVID-19. This could be especially useful for health care providers who are working with COVID-19 patients. 

Q: Can we get herd immunity for COVID-19? If we get it in our region, can we avoid the infection?

Krishna: No, for any new infection, that is very difficult to achieve. 

First it is extremely difficult to predict things during  pandemics because situations change every day. And all things have to be re-looked and re-analysed frequently as new data comes in. 

But herd immunity without a vaccine is by definition not a preventative measure.

Herd immunity is an epidemiological concept that describes the state where a population – usually of people – is sufficiently immune to a disease that the infection will not spread within that group. In other words, enough people can't get the disease – either through vaccination or natural immunity – that the people who are vulnerable are protected. 

Experts explain like this: 

For example, let's think about mumps. Mumps is a very infectious disease that, while relatively benign, is very uncomfortable and sometimes causes nasty life long complications. It's also vaccine-preventable, with a highly effective vaccine that has made the disease incredibly rare in the modern age.

Mumps has a basic reproductive rate (R0) of 10-12, which means that in a population which is entirely susceptible – meaning no one is immune to the virus – every person who is infected will pass the disease on to 10-12 people.

This means that without vaccination roughly 95 percent of the population gets infected over time. But even with something that is this infectious, there are still some people – 5 percent of the population – who don't get sick, because once everyone else is immune there's no one to catch the disease from.

We can increase that number by vaccinating, because vaccination makes people immune to infection, but it also stops infected people passing on the disease to everyone that they otherwise would. If we can get enough people immune to the disease, then it will stop spreading in the population.

For mumps, you need 92 percent of the population to be immune for the disease to stop spreading entirely. This is what's known as the herd immunity threshold. COVID-19 is, fortunately, much less infectious than mumps, with an estimated R0 of roughly 3.

With this number, the proportion of people who need to be infected is lower but still high, sitting at around 70 percent of the entire population.

Which brings us to why herd immunity could never be considered a preventative measure.

If 70 percent of your population is infected with a disease, it is by definition not prevention. How can it be? Most of the people in your country are sick! And the hopeful nonsense that you can reach that 70 percent by just infecting young people is simply absurd. If only young people are immune, you'd have clusters of older people with no immunity at all, making it incredibly risky for anyone over a certain age to leave their house lest they get infected, forever.

It's also worth thinking about the repercussions of this disastrous scenario – the best estimates put COVID-19 infection fatality rate at around 0.5-1 percent. If 70 percent of an entire population gets sick, that means that between 0.35-0.7 percent of everyone in a country could die, which is a catastrophic outcome.

With something like 10 percent of all infections needing to be hospitalised, you'd also see an enormous number of people very sick, which has huge implications for the country as well.

The sad fact is that herd immunity just isn't a solution to our pandemic woes. Yes, it may eventually happen anyway, but hoping that it will save us all is just not realistic. 

Q: Can mosquitoes transmit corona virus?

Krishna: There is no evidence to show that mosquitoes can transmit COVID19. 

Female mosquitoes need the nutrition contained in blood to help develop their eggs. Viruses take advantage of this biological requirement of mosquitoes to move from host to host.

But for a mosquito to become infected, it first needs to bite an infected animal, such as a bird or kangaroo, or a person. Mosquitoes can transmit a number of viruses, including dengue, yellow fever, chikungunya, Zika and Ross River virus. They can also transmit malaria, which is caused by a parasite.

But they can’t transmit many other viruses, including HIV and Ebola. 

For HIV, mosquitoes themselves don’t become infected. It’s actually unlikely a mosquito will pick up the virus when it bites an infected person due to the low concentrations of the HIV circulating in their blood.

For Ebola, even when scientists inject the virus into mosquitoes, they don’t become infected. One study collected tens of thousands of insects during an Ebola outbreak but found no virus.

The new coronavirus is mostly spread via droplets produced when we sneeze or cough, and by touching contaminated surfaces.

Although coronavirus has been found in blood samples from infected people, there’s no evidence it can spread via mosquitoes.

Even if a mosquito did pick up a high enough dose of the virus in a blood meal, there is no evidence the virus would be able to infect the mosquito itself.

And if the mosquito isn’t infected, it won’t be able to transmit it to the next person she bites. 

Why only some viruses can be transmitted by mosquitoes  and not all?

It’s easy to think of mosquitoes as tiny flying dirty syringes transferring droplets of infected blood from person to person. The reality is far more complex.

When a mosquito bites and sucks up some blood that contains a virus, the virus quickly ends up in the gut of the insect.

From there, the virus needs to infect the cells lining the gut and “escape” to infect the rest of the body of the mosquito, spreading to the legs, wings, and head.

The virus then has to infect the salivary glands before being passed on by the mosquito when it next bites.

This process can take a few days to over a week.

But time isn’t the only barrier. The virus also has to negotiate getting out of the gut, getting through the body, and then into the saliva. Each step in the process can be an impenetrable barrier for the virus.

This may be straightforward for viruses that have adapted to this process but for others, the virus will perish in the gut or be excreted.

Q: Why don't some people adhere to quarantine?

Krishna: Quarantine will not work if people do not adhere to it.

Research*1 showed that people vary in their adherence to quarantine and from the eight studies that reported on this, adherence rates of quarantined individuals ranged from 0 to 92.8%.

One of the major factors affecting adherence to quarantine is knowledge about the infection and the quarantine protocol, according to the study. If instructions or language are unclear then people tend to make up their own rules. Social pressure from others to comply with quarantine is also important.

Cultural factors also played a role, according to the researchers, and when caring for others is inherent in a culture this could mean people might break quarantine in order to follow this cultural norm.

Some religious leaders also discourage quarantine because of overconfidence in their faith. 

If people believed that quarantine was beneficial in controlling the outbreak then adherence would be better, particularly if it could be observed in a slowing in the spread of the outbreak. In addition, when the disease itself is believed to be more risky, adherence to quarantine was better.

Practical issues were also influential with fear of running out of supplies and loss income both affecting whether people broke quarantine.

 People vary in their adherence to quarantine during infectious disease outbreak and to improve this public helath officials should provide a timely, clear rationale for quarantine and information about protocols and emphasize social norms to encourage this altruistic behavior.

The effectiveness of quarantine depends on how many people do it so it is important to know what makes people more likely to comply. Research shows that information and knowledge around the quarantine are central to its effectiveness.

In the era of 'fake news' consistent messaging is difficult but leaving the information needs of the public unmet can be dangerous. Public health teams should provide clear, authoritative information where needed, and then check the messages are getting through.

*1 https://www.sciencedirect.com/science/article/pii/S0033350620300718...

Q: Where did CRISPR tech come from?

Krishna: Biomimicry! Many bacteria use a system known as CRISPR-Cas to defend themselves against infection by viruses called phages. This system protects the bacterial cell by taking a short length of DNA from the phage and inserting this 'spacer' into its own genome. If the bacterial cell becomes re-infected, the spacer allows the cell to recognize the phage and stop it from replicating by cutting and destroying its DNA. Bacteria with these spacers survive infections and pass their spacers on to their progeny, creating a population that is resistant to the phage.

Scientists just mimicked this process. 

Q: A famous medical Doctor says, corona virus particles can't travel through air! What do you say about this? A video is circulating on Whats app too.

https://www.youtube.com/watch?v=oJ4NROb_49k

Krishna: Yes, several people asked me this question after watching his videos.

I even commented on his videos saying that his assessment mounts to misinformation. I gave him these links to papers  that say he is not correct: 

https://medicalxpress.com/news/2020-04-important-speech-transmittin...

https://medicalxpress.com/news/2020-04-coronavirus-scientists.html?...

This 's my comment:

Q: What is Hantavirus? Is it dangerous too?

Krishna: NO. Hantavirus is certainly not one we should particularly concerned about right now.

“Orthohantavirus” - commonly known as hantavirus – is a very, very rare virus. There have never been confirmed human cases in India. The last two reported confirmed cases worldwide were in January in Bolivia and Argentina. There was also a recent report of a single case in China but there’s no indication of any sort of spread.

It is in a class of diseases called zoonoses, meaning it is a virus transmitted from animals to human. In this case, the animal in question is rodents (usually rats). Hantaviruses can cause severe disease, including bleeding and kidney failure.

According to the US Centers for Disease Control and Prevention (CDC), hantavirus is spread from several species of rodents in their urine, droppings, and saliva. It is thought that transmission occurs when they breathe in air contaminated with the virus.

CDC also reports : 

• • if a rodent with the virus bites someone, the virus may be spread to that person, but this type of transmission is rare;
  • scientists believe that people may be able to get the virus if they touch something that has been contaminated with rodent urine, droppings, or saliva, and then touch their nose or mouth;
  • scientists also suspect people can become sick if they eat food contaminated by urine, droppings, or saliva from an infected rodent.

  • There isn't anything to worry about hantavirus right now.