Jul
24
2022

How Covid-19 Causes Smell Loss

Posted by: admin in Categories: News.

Temporary loss of smell, or anosmia, is the main neurological symptom and one of the earliest and most commonly reported indicators of COVID-19. Studies suggest it better predicts the disease than other well-known symptoms such as fever and cough, but the underlying mechanisms for loss of smell in patients with COVID-19 have been unclear.

Now, an international team of researchers led by neuroscientists at Harvard Medical School has identified the olfactory cell types most vulnerable to infection by SARS-CoV-2, the virus that causes COVID-19.

Surprisingly, sensory neurons that detect and transmit the sense of smell to the brain are not among the vulnerable cell types.

Reporting in Science Advances on July 24, the research team found that olfactory sensory neurons do not express the gene that encodes the ACE2 receptor protein, which SARS-CoV-2 uses to enter human cells. Instead, ACE2 is expressed in cells that provide metabolic and structural support to olfactory sensory neurons, as well as certain populations of stem cells and blood vessel cells.

The findings suggest that infection of nonneuronal cell types may be responsible for anosmia in COVID-19 patients and help inform efforts to better understand the progression of the disease.

“Our findings indicate that the novel coronavirus changes the sense of smell in patients not by directly infecting neurons but by affecting the function of supporting cells,” said senior study author Sandeep Robert Datta, associate professor of neurobiology in the Blavatnik Institute at HMS.

This implies that in most cases, SARS-CoV-2 infection is unlikely to permanently damage olfactory neural circuits and lead to persistent anosmia, Datta added, a condition that is associated with a variety of mental and social health issues, particularly depression and anxiety.

“I think it’s good news, because once the infection clears, olfactory neurons don’t appear to need to be replaced or rebuilt from scratch,” he said. “But we need more data and a better understanding of the underlying mechanisms to confirm this conclusion.”

A majority of COVID-19 patients experience some level of anosmia, most often temporary, according to emerging data. Analyses of electronic health records indicate that COVID-19 patients are 27 times more likely to have smell loss but are only around 2.2 to 2.6 times more likely to have fever, cough or respiratory difficulty, compared to patients without COVID-19.

Some studies have hinted that anosmia in COVID-19 differs from anosmia caused by other viral infections, including by other coronaviruses.

For example, COVID-19 patients typically recover their sense of smell over the course of weeks — much faster than the months it can take to recover from anosmia caused by a subset of viral infections known to directly damage olfactory sensory neurons. In addition, many viruses cause temporary loss of smell by triggering upper respiratory issues such as stuffy nose. Some COVID-19 patients, however, experience anosmia without any nasal obstruction.

Obtained from: Harvard Medical School

0 Comments
Jul
16
2022

The first hints that a vaccine can train people’s immune system to fight coronavirus have been reported by a company in the US.

Moderna said neutralising antibodies were found in the first eight people who took part in their safety trials.

It also said the immune response was similar to that in people infected with the actual virus.

Larger trials to see whether the jab protects against infection are expected to start in July.

Work on a coronavirus vaccine has been taking place at unprecedented speed, with around 80 groups around the world working on them.

Moderna was the first to test an experimental vaccine, called mRNA-1273, in people.

The vaccine is a small snippet of the coronavirus’s genetic code, which is injected into the patient.

It is not capable of causing an infection or the symptoms of Covid-19, but is enough to provoke a response from the immune system.

The vaccine trials, run by the US government’s National Institute of Allergy and Infectious Diseases, showed the vaccine led to the production of antibodies which can neutralise the coronavirus.

However, testing for these neutralising antibodies has only taken place on the first eight, out of 45, people on the trial.

  • A SIMPLE GUIDE: How do I protect myself?
  • IMPACT: What the virus does to the body
  • RECOVERY: How long does it take?
  • LOCKDOWN: How can we lift restrictions?
  • ENDGAME: How do we get out of this mess?

The people on the trial were taking either a low, middle or high dose. The highest dose was linked to most side-effects.

However, Moderna said that even people taking the lowest dose had antibodies at the same levels seen in patients who recover from Covid-19.

And antibodies “significantly exceeded” those in recovered patients for people on the middle dose.

The study is known as a phase 1 trial as it is designed to test whether the vaccine is safe, rather then whether it is effective.

It will take larger trials to see if people are protected against the virus. However, experiments on mice showed the vaccine could prevent the virus replicating in their lungs.

“These interim phase 1 data, while early, demonstrate that vaccination with mRNA-1273 elicits an immune response of the magnitude caused by natural infection,” said Dr Tal Zaks, chief medical officer at Moderna.

“These data substantiate our belief that mRNA-1273 has the potential to prevent Covid-19 disease and advance our ability to select a dose for pivotal trials.”

Moderna said it was hoping to start a large-scale trial in July, and that it was already investigating how to manufacture the vaccine at scale.
Oxford vaccine

A vaccine pioneered by the University of Oxford is also being tested in people, but there are no results from those trials yet.

However, concerns have been raised about the results of experiments in monkeys.

Tests showed vaccinated animals had less severe symptoms and did not get pneumonia. However, they were not completely protected from the virus and signs of it were detected at the same level in the monkeys’ noses as in unvaccinated animals.

Prof Eleanor Riley, from the University of Edinburgh, said: “If similar results were obtained in humans, the vaccine would likely provide partial protection against disease in the vaccine recipient but would be unlikely to reduce transmission in the wider community.”

However, until human trials have been performed it is impossible to know how the vaccine will perform in people.

Obtained from: https://www.bbc.com/news/health-52677203

0 Comments
Jul
05
2022

It may soon be harder to cross the border into any East African country without a yellow fever certificate if a new policy is adopted. PHOTO | FILE | NATION MEDIA GROUP

In Summary

  • According to the new guidelines, East Africans planning to go to any of the six countries within the EAC will be required to show proof that they have been vaccinated against yellow fever 10 days before their actual travel date.

By ELIZABETH MERAB

It may soon be harder to cross the border into any East African country without a yellow fever certificate if a new policy to reintroduce the stringent measures of old is adopted.

According to the new guidelines, East Africans planning to go to any of the six countries within the EAC will be required to show proof that they have been vaccinated against yellow fever 10 days before their actual travel date.

This, therefore, means that anyone without a valid yellow fever vaccination certificate will be denied entry to either Kenya, Tanzania, Uganda, Rwanda, Burundi or Sudan, explained Dr Michael Katende, the acting head of the health department at the East African Community Secretariat in Arusha.

“We continue to have our surveillance system in place, and shall continue to insist on the yellow fever certificate especially if you are coming from a country which has been known to have few outbreaks,” said Dr Katende.

The request for the certificates and insistence on using the vaccination is for protection, Dr Katende said, was prompted by the recent increased in outbreaks in the region.

“We are also alive to the fact that by virtue of the EAC region bordering DRC, a country with a huge forest cover and biodiversity, we need to heighten our surveillance,” he said.

Yellow fever is a viral infection spread by a type of mosquito. The infection is most common in Africa and South America, affecting travellers to and residents of those areas.

ROUTINE SURVEILLANCE

Two weeks ago, Ugandan Health Ministry declared a yellow fever outbreak after laboratory test confirmed cases were reported from Koboko and Masaka districts, located in the northern and central regions of the country, according to a bulletin from the WHO African regional office.

Officials identified two cases of yellow fever in March, when routine surveillance showed the virus in an 80-year-old woman and a 10-year-old girl, neither of whom had been vaccinated against it.

“On May 14, the Ministry of Health notified WHO of a yellow fever outbreak in the Koboko and Masaka districts located in the Northern and Central region of the country respectively. The outbreak was declared in-country on May 6 following laboratory confirmations from the regional yellow fever reference laboratory, the Uganda Virus Research Institute,” says the WHO status report.

In mild cases, yellow fever causes a fever, headache, nausea and vomiting. But it can become more serious, causing heart, liver and kidney problems along with bleeding (haemorrhaging). Up to 50 per cent of people with the more-severe form of yellow fever die of the disease.

DEADLY AND MOSQUITO-BORNE

Although there is no specific treatment for yellow fever, getting vaccinated before travelling to an area in which the virus is known to exist can protect you from the disease.

Rapid response teams were sent to the villages of both patients and found an additional seven cases of yellow fever, and a “substantial population of unvaccinated individuals due to immigration and missing the yellow fever reactive vaccination campaign, which was conducted in 2016.”

“Although the occurrences are on and off, we still have outbreaks of the disease. We already have enough outbreaks within East Africa, prompting us to maintain their surveillance,” added Dr Katende.

The region has been on high alert since 2016 when there was an outbreak in Angola.

Last year, the disease seemed to get inches closer after the deadly mosquito-borne disease killed 10 people in southwestern Ethiopia forcing the World Health Organisation to release more than a million doses of yellow fever vaccine from its emergency stockpile.

In Africa, Tanzania and South Africa require a valid yellow fever certificate from all citizens and non-citizens (over one year of age) travelling from a yellow fever risk country.

In South Africa, if a traveller is unable to produce a valid yellow fever vaccination certificate at the point of entry, entry is denied and the traveller is placed under quarantine until they are vaccinated.

In East Africa, only Tanzania demands proof of vaccination against yellow fever from visitors upon arrival at the airport. Uganda, however, tightened its rules in 2016 following a WHO recommendation that the country review its yellow fever vaccination policy, and that people from high-risk countries show proof of vaccination.

Kenya followed suit by putting the country on high alert.

Vaccination certificates are routinely checked at points of entry for travellers arriving from countries designated as high risk for yellow fever transmission. Persons who have been in transit exceeding 12 hours through the airport of a country with high risk of yellow fever transmission are also required to produce proof of vaccination upon arrival.

Travellers with an exemption certificate due to medical reasons will be allowed entry, but will be placed under quarantine and/or will be required to report any fever or other symptoms to health authorities.

The WHO guidelines require countries at risk of yellow fever to obtain vaccination certificates from individuals travelling from areas determined by the WHO to be at risk; it also recommends disinfecting aircraft, ships, tyre-casing consignments and other modes of transportation coming from a risk area.

Source: https://www.theeastafrican.co.ke/scienceandhealth/East-Africa-tightens-travel-to-contain-yellow-fever-spread/3073694-5149738-yn5tttz/index.html

0 Comments