Viruses didn’t become ubiquitous by being wimps: From the rhinoviruses that cause the common cold to the new coronavirus that has spread across the world, they are able to survive on surfaces far away from the living cells that they need in order to reproduce.
How long they can lurk before a living organism comes along to infect depends on the kind of surface and the properties of the virus: The Covid-19 virus, according to a new study, sticks around on plastic surfaces for up to three days, but for a shorter period on metals.
Rhinoviruses can survive on human skin for hours, which is why shaking hands with someone who has a cold is a good way to catch it. Influenza viruses remain infectious for up to 48 hours after landing on nonporous surfaces such as stainless steel or plastic such as that in computer keyboards, but that seems like the outer limit: A 2011 study found that the H1N1 flu virus that caused the 2009 pandemic could be recovered from glass, stainless steel, plastic, and aluminum for up to 48 hours, but most was gone after nine hours. Both cold and flu viruses survive for much shorter times on porous surfaces such as cloth, paper, or tissue, with very little infectious virus remaining after four hours.
Viruses covered in “envelopes” have the most trouble surviving outside a living cell. On surfaces, the surrounding light, heat, and dryness break down the envelope, killing the virus. (Porous surfaces pull moisture away from viruses that land on them, accelerating the destruction of the envelope.) Most rhinoviruses have such envelopes; so do some influenza viruses. Norovirus doesn’t, enabling it to last longer in the environment.
Then there’s the new coronavirus. Its survival on surfaces is similar to that of the SARS virus, to which it’s related. On plastic, after eight hours only 10% of what researchers deposited was still there, according to a study published on Tuesday in the New England Journal of Medicine. But the virus didn’t become undetectable until after 72 hours. On stainless steel, the numbers began plummeting after just four hours, becoming undetectable by about 48 hours. On copper and cardboard, virus was undetectable by eight hours and 48 hours, respectively.
The fewer the virus particles on a surface, the lower the chances that someone touching it will become infected. “You have to get a certain level of virus exposure to be infected,” said Ross McKinney, chief scientific officer of the American Association of Medical Colleges. And infection cannot happen through the skin: to “self inoculate,” one must transfer virus from, say, the fingers to the nose or eyes, where it can enter the body via mucus membranes.
But because the virus that causes Covid-19 is, like other microbes, so durable, thoroughly washing hands after touching surfaces that anyone else might have touched — or not touching them in the first place — is the first line of defense against infection.
SOURCE: By SHARON BEGLEY @sxbegleMARCH 19, 2020
The anti-malaria drug: chloroquine
Chloroquine is a cheap, widely available drug that has been routinely used since 1945 against malaria and other conditions and can be safely taken by pregnant women and children. Lab studies found the antiviral drug was effective against the coronavirus, at least in a petri dish, and results from a small French study in 24 patients, announced this week, suggested that it could quicken recovery.
Doctors said 25% of patients who received the drug tested positive for the virus after six days, compared with 90% of those who did not receive it. Chloroquine and a related drug, hydroxychloroquine, are among the four treatments tested in an international clinical trial, announced on Wednesday by the World Health Organization (WHO), and the UK has added chloroquine to its list of medicines under export controls.
The HIV treatment drug: Kaletra
Kaletra is a combination of two antiviral medicines, lopinavir and ritonavir, normally used to treat HIV, which lab studies suggested held promise as a potential Covid-19 treatment. However, these hopes suffered a significant setback this week with one of the first major studies of 200 seriously ill patients from China finding no benefit. The study is not the end of the road: it is possible that the drug could be effective if given earlier on, or to less severely ill patients. The WHO has included Kaletra in a major multi-country trial launched this week.
The anti-flu drug: favipiravir
The Japanese flu drug, made by a subsidiary of Fujifilm, has created a stir by more than halving the time that people with Covid-19 test positive for the virus. A Chinese trial in 340 people showed that the virus tended to be cleared in four days in those who received the drug, versus 11 days in those who went without. Chest scans supported the findings, revealing less damage in those who took the drug. But the antiviral, also known as Avigan, may need to be given before virus levels peak in the body. A Japanese health official told the Mainichi Shimbun newspaper that it did not appear to work as well in severely ill people, in whom the virus had had more time to replicate.
The Ebola drug: remdesivir
Remdesivir was originally developed as an Ebola treatment, but the drug has emerged as a frontrunner among potential antiviral drugs to combat Covid-19. The enthusiasm comes from studies that show that it works against Sars and Mers, two other coronaviruses that are more lethal but less transmissible. The drug works by shutting off the virus’s ability to replicate itself inside cells. This means it is most likely to be effective when a person has just caught the bug and the virus is still reproducing in the upper respiratory tract. One reason for caution is that early data suggest people may already have high levels of the virus when they start showing symptoms. Multiple trials are under way to evaluate remdesivir in China, the US and Asia, with the first results due in April.
Antibody therapies Advertisement
Doctors in China have treated some critically ill patients with the blood plasma of recovered patients, an approach that dates back to the Spanish flu pandemic of 1918. The logic is that the blood should contain antibodies to help fight off infection. Downsides include the difficulties of scaling up the method for widespread use, the risk of transmitting other diseases and that the relevant antibodies are only present in small amounts, so the treatment, if effective at all, is far from optimal. A number of teams, including the US company Regeneron, are working on the hi-tech equivalent of serum therapy. Regeneron says it is a few weeks away from identifying two powerful antibodies that protect against Covid-19, which it will then manufacture synthetically and turn into a therapeutic cocktail, with a view to starting human trials in the summer. If successful, an antibody therapy could be used as both a treatment and a prophylactic to protect health workers and other high-risk groups.
The UK biotech firm Synairgen has been given fast-track approval to trial a lung-disease drug in Covid-19 sufferers. The compound, interferon beta, forms part of the lung’s natural defence system against viruses and was originally developed for patients with chronic obstructive pulmonary disorder, or COPD. The hope is that administering interferon beta boosts the body’s ability to fight the virus, especially in those who have weakened immune systems. It was identified in February by the WHO as the only therapy in phase-2 trials that can be inhaled, meaning patients can administer it themselves through a small battery-operated nebuliser.