Can Microwaving Mail Kill the Virus? Can You Get COVID-19 Twice? Answering Your Questions About COVID-19 

Editor's note, May 7, 2020: You can read our previous COVID-19 Q&A with Dr. Clark by clicking here or read our follow up article by clicking here.

The outbreak of COVID-19 has prompted many people to take precautions to keep themselves safe. Last week, Dr. Justin Clark, PhD, answered a variety of key questions related to the virus. However, day by day, we are learning a more about COVID-19. This has prompted follow-up questions by QNL readers on our blog and Facebook page. Below is a list of these questions, answered by Dr. Clark.  

Editor's note: This article was initially posted during the summer of 2020 and has not been updated to reflect the current scientific discoveries of COVID-19. For more up-to-date information, please refer to the Centers for Disease Control and Protection website. 

This is Part 2 of our COVID-19 series. Please see the other parts below: 

  1. Coronavirus (COVID-19) - What You Should Know
  2. What's the Safest Way to Shop? Are Certain Blood Types at Higher Risk? Answering Your Questions about COVID-19
  3. The What We Know Now: The Latest Updates to Your Covid-19 Questions - Q&A with Gabriel Espinoza, Md. What Disinfectants Kill Covid-19? What Is the Progress of a Vaccine? Are Cloth Masks Effective? Are We Experiencing A Second Wave? Are Kids at Risk?
Picture of Dr. ClarkPicture of Dr. Clark

Dr. Clark’s Background: 

Dr. Clark graduated with a B.S. in Biology from the University of North Carolina and was awarded a Ph.D. in Integrative Molecular and Biomedical Sciences from Baylor College of Medicine. He has researched bacterial and viral pathogens for over 10 years. All opinions are his own. 

QNL: Why is there the need to shut everything down and cancel everything having to do with human contact? The chances of getting it, unless in a high-risk area, are still very low. It is also said that the virus is spread by cough droplets and by people with no symptoms, so how are they spreading it? 

Dr. Clark: At this point, cancelling events is more about so called “social distancing”. This is a new idea for the public, but it is basically about limiting how many people get exposed to the virus at once. Here is a visual made by Dr. Siouxsie Wiles and Toby Morris to help explain it.

How to break the infection cycle for COVID-19How to break the infection cycle for COVID-19

The Washington Post also has a good collection of graphs explaining social distancing. They can be found here.

Coughing and sneezing are the easiest way for droplets to be spread distances more than a few feet, but droplets are also produced when you breath. As a result, people can be exposed to the virus by talking face-to-face, kissing, hugging, etc. If you’re asymptomatic, you are also touching your face and touching objects, which other people can be infected by. Asymptomatic people may also spread it through the oral-fecal route. That’s according to one case-study, which found viral ribonucleic acid in stool samples of an asymptomatic Chinese child 26 days after exposure to the virus.1 Here is a slide presentation from the CDC that is a good primer on aerosolized particle transmission. 

QNL: First, they said the virus would only survive on surfaces for 6 hours. Now, they are saying it can live on surfaces for days. Is it getting worse? How long does it live on mail, produce/groceries, the streets (they are cleaning cities/streets in other countries), sand/on the beach, and takeout food containers? Can it survive in water? Does heat change how long it lives on surfaces and in the air? 

Dr. Clark: I haven’t heard of any reports that say it can only survive for 6 hours for this particular virus, unless the surface is copper. However, the virus doesn’t seem to be getting worse. Most of what we know about survivability we get from studies on other coronaviruses that infect humans, including ones that cause the common cold, SARS, and MERs.2,3 These studies suggest that coronaviruses are able to remain infectious for weeks at refrigerated temperatures (about 40° F) and able to survive multiple rounds of freezing. However, these viruses are not very heat stable. It is generally agreed that temperatures of 132° F for 30 minutes will inactivate the virus.3,4 Coronaviruses are stable in water.5  

The biggest problems with trying to give definitive answers to how long it can survive on different surfaces is the fact that the survivability of coronaviruses and SARS-like coronaviruses depend heavily on the environment. The WHO has a table of survival time for SARS under different conditions that illustrates this, found here.  

I believe the safest thing to do is assume that COVID-19 can survive 2-3 days on anything you bring in. I base this on the recent NIH study that found the virus can survive for 2 to 3 days on metal and plastic at room temperature and moderate humidity.6  

If you order food takeout, experts recommend that you remove food from the container it came in, dispose of the container properly, and then wash your hands thoroughly. The same can be done for mail, or you can simply leave the mail in the garage or a closet for a 2-3 days until any possible viral particles are no longer viable.  

Prevent COVID-19Prevent COVID-19

QNL: Will microwaving mail (or any object) for a minute or two will kill the virus? Will high heat or freezing it kill the virus? 

Dr. Clark: I wouldn’t recommend microwaving anything other than food. The only thing worse than riding out a pandemic, is riding out a pandemic somewhere other than home because you burned your house down! There are currently no cases of a person being infected through the mail, but if you want to be safe, you can quarantine your mail for 2 to 3 days in the garage or in a closet. Alternatively, you can open your mail and dispose of the envelope or outer packaging and then wash your hands thoroughly.   

Freezing and low temperature does not appear to have much effect on coronaviruses.2 These viruses are susceptible to heat though. They can be inactivated at temperatures above 132° F for 30 minutes.3,4 For reference, modern dryers tend to run between 125° and 135° F. This is a convenient way to clean your clothes if you can’t wash them. But you should follow guidelines and not put anything in the dryer that is not meant to go there.

QNL: What about its relationship with ibuprofen?  

Dr. Clark: This is a bit complicated. French doctors apparently observed that otherwise healthy people who were taking ibuprofen tended to take a turn for the worse. This was then tied to a commentary in The Lancet that suggested ibuprofen could increase the amount of ACE2 (SARS-CoV-2 receptor in humans), but they offered no evidence to support that claim.7  

It should be noted that there have been no scientific studies looking specifically at the link between COVID-19 and ibuprofen. This is important because informal observations are not always reliable. For example, people who take ibuprofen may have something else in common or be more likely to do something else that makes them more susceptible to the virus. There is also the possibility that the doctors are unconsciously biased through no fault of their own. For a more real-life example, you may notice more yellow cars on the road after you buy a yellow car, but that doesn’t necessarily mean that more people are driving yellow cars. This is why it is important to do controlled scientific studies. 

That being said, you can take Tylenol/acetaminophen instead of ibuprofen if it is available and you want to be cautious.     

QNL: Can you get COVID-19 more than once? If so, how long after you fight off the virus can you contract it again?  

Dr. Clark: This has a lot of people worried, so I’ll go in depth below, but to summarize: there is no scientific evidence to suggest people can get re-infected within weeks of recovering. There is reason to believe protection may last at least a year.  

Most experts think it is unlikely that most people can be re-infected in the short-term. It is more likely that the reports of reinfection are either rare events where the person did not produce an adequate antibody response, or a situation where that the person had not actually recovered and instead had a false negative. 

Like with other aspects of SARS-CoV-2, we look to other coronaviruses for clues. Coronaviruses that cause the common cold do not elicit a strong immune response, but the response generally lasts on a scale of years rather than weeks. Though in one study healthy volunteers were able to be infected twice with the same strain a year apart.8 A better comparison probably comes from SARS because it causes a more severe disease. With SARS, people produced protective antibodies (that is, antibodies that protect against the virus) for up to two years after being infected, though the amounts of these antibodies decreased significantly after 16 months.9 Until we know more about COVID-19 specifically, this data is probably the best we have.    

So, as of right now, we do not know how long this antibody response for SARS-CoV-2 lasts. But a recent pre-peer reviewed article showed that rhesus monkeys could not be immediately reinfected with SARS-CoV-2, which is good news and a good start.10 In the coming months we’ll be able to answer this more clearly.   

Person sitting on a couch with a box of tissues and medicinesPerson sitting on a couch with a box of tissues and medicines

QNL: Any idea as to when this will die down and get better in the US? 

Dr. Clark: Unfortunately, no one really knows because it depends a lot on what measures we take to slow the spread of the disease (shelter-in-place orders, school closures, bans on gatherings, etc.) and how effective they are. A lot of people are looking to the model by a super-star group of epidemiologists at Imperial College London as a guide. Their model suggests that without any efforts to slow the pandemic, it would peak in different states between mid-May and late-June.11 However, if social distancing measures work, the peaks will be less intense, but the pandemic will last longer. 

Despite the effectiveness of social distancing, there are a lot of things to consider. For example, a full “lockdown” may prevent the pandemic from peaking, but it is almost certain that another wave will come through and the lockdown will need to be put in place again.  

Personally, I’m hoping that social distancing and lockdown orders will slow down the virus long enough for us to get ahead of it. It will take a few weeks before we will know if the measures are working. Then I’m hoping that contact-tracing and aggressive testing will allow most people to get back to their lives. If this happens, there will be sporadic outbreaks and temporary lockdowns probably for at least 12 to 18 months until a vaccine or effective treatment can be found. 

QNL: POTUS has announced that the FDA has fast tracked treatment for COVID-19. What does this really mean?  

Dr. Clark: I believe the POTUS was referring to “Compassionate Use”, which is basically just approval to use an unproven drug on patients. They’re doing this so that the drugs can be used immediately without proving efficacy against COVID-19 in clinical trials. It helps that the drugs that have been approved so far for COVID-19 have already gone through clinical trials to prove their safety.  

QNL: Has it mutated? Can it? What does that mean for us if it does? Will it last longer and will vaccines still be effective? How long until the vaccine is available? SARS was an issue in 2003, but even today there is no vaccine for it. Why is this? Wouldn’t that have helped prevent this epidemic?  

Dr. Clark: Luckily, coronaviruses mutate slower than many other viruses because they contain a protein to lower mutation rates. However, organisms are always mutating, even if the rate is low, so there have already been changes in the virus’ genetic code as it has spread. At the moment, there is no evidence to suggest that any of the mutations have made it deadlier or more severe. If it does gain a mutation that changes its characteristics, that doesn’t necessarily mean a vaccine would stop working.  

A vaccine will probably take at least 12-18 months to develop. This is because safety trials need to be performed before the vaccine is used on a large percentage of Americans. 

Several vaccines were in production for SARS, and many of those are being tested for efficacy against SARS-CoV-2. But unfortunately, most people just lost interest in SARS. When people lose interest, funding tends to dry up—and clinical trials are very expensive to run. A vaccine may have prevented this pandemic if there was enough cross-reactivity, but sadly we may never know for sure. 

QNL: How long is an infected person be considered a carrier or a risk to others? If a person has contracted the virus, does the severity of the symptoms affect how long the person is contagious? After someone has recovered from COVID-19, should they be re-tested to determine whether or not they are still a carrier of the virus and whether they can infect others? 

Dr. Clark: The answer to all those questions is really that we don't know. There was a case-study of an asymptomatic 10-year-old in China who was found to have SARS-CoV-2 RNA in his stool samples up to 26 days after his last exposure but it isn’t known whether he was contagious or not.1 China was having recovered patients self-isolate for an additional 14 days after a sizable percentage of people tested positive after being declared recovered. But as far as I know, no one was infected by these patients. It seems more likely to me that these individuals had false negatives that gave them a false “recovered” status or that the virus RNA stays in a person at barely detectable levels for a short time after recovery (this isn’t uncommon). But keep in mind, testing positive for viral RNA does not necessarily mean that you are contagious. 

If asymptomatic carriers are found, I am not sure what the current protocol is if testing isn't available. Otherwise, they'd probably be asked to quarantine until testing negative, just in case.

Box of tissuesBox of tissues

QNL: Once you start showing symptoms, are the fever and cough usually immediate? Or is it a gradual progression to that point? What is the timeline of symptoms and the virus as it runs its course? Also, once symptoms start showing, how long on average does it take for the immune system to kill the virus and for symptoms to clear up (for the 80% of mild cases)? 

Dr. Clark: It is hard to nail down a “typical” case of COVID-19. The first symptom appears to most often be a fever and/or cough. However, some people have reported first experiencing abdominal cramps and diarrhea while others have reported headaches, sore throats, or shortness of breath. For mild cases, it seems to resemble the common cold or the flu, taking about a week (but sometimes more) to show improvement after symptoms first manifest. The 80% of “mild” cases also include what could be called “moderate” cases. These are cases where pneumonia develops, but not to the point of needing hospitalization. From what I understand, these patients also tend to start getting better a week after showing symptoms but may take longer to fully recover. 

In contrast to mild forms of the disease, patients with severe forms tend to go downhill during the second week of showing symptoms. These patients have a more severe form of pneumonia and require oxygen support. 

However, if the patient is very sick before contracting COVID-19, they may go downhill rapidly, as was seen in the Life Care Center of Kirkland. 

QNL: Is COVID-19 more deadly than other coronaviruses? 

Dr. Clark: The fatality rate is approximately 10% for SARS and 35% for MERS compared to the WHO’s current estimate of 3.4% for SARS-CoV-2. 

QNL: What are your thoughts on the cold arrest procedure? Does it help? 

Dr. Clark: I’m not very familiar with that procedure, but from what I understand, I wouldn’t recommend it. The air coming out of a hair dryer may be hot enough to kill viruses from an inch away, but you aren’t going to be able to get it that hot in your nasal cavity without burning yourself. And you certainly wouldn’t be able to get it that hot for the 15+ minutes you would need to kill a coronavirus.  

And if the virus is already in your nose and sinuses, you’re breathing those viral particles in and are probably already infected. 

QNL: What are your thoughts on Everlywell's COVID-19 home detection test? Will it be effective?

Dr. Clark: I really can’t speak to the efficacy of this tests. I didn’t see much in the way of technical information or control studies. There is no reason why a home test couldn’t work in theory but given how inaccurate tests have been for every country and how much sample collection technique can affect the results, I would be weary of trusting the results without more information.

QNL: Thank you, Dr. Clark, for taking the time to answer our questions. We appreciate your expertise.  

You can read our previous COVID-19 Q&A with Dr. Clark by clicking here or read our follow up article by clicking here.

If you have a question about COVID-19, please leave a comment below. It may be featured in our next Q&A with Dr. Clark!


  1. Tang, A. et al. Detection of Novel Coronavirus by RT-PCR in Stool Specimen from Asymptomatic Child, China. Emerg. Infect. Dis. 26, (2020). 
  2. Lamarre, A. & Talbot, P. J. Effect of pH and temperature on the infectivity of human coronavirus 229E. Can. J. Microbiol. 35, 972–974 (1989). 
  3. Rabenau, H. F. et al. Stability and inactivation of SARS coronavirus. Med. Microbiol. Immunol. 194, 1–6 (2005). 
  4. Kampf, G., Todt, D., Pfaender, S. & Steinmann, E. Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents. J. Hosp. Infect. 104, 246–251 (2020). 
  5. Casanova, L., Rutala, W. A., Weber, D. J. & Sobsey, M. D. Survival of surrogate coronaviruses in water. Water Res. 43, 1893–1898 (2009). 
  6. van Doremalen, N. et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. N. Engl. J. Med. NEJMc2004973 (2020) doi:10.1056/NEJMc2004973. 
  7. Fang, L., Karakiulakis, G. & Roth, M. Are patients with hypertension and diabetes mellitus at increased risk for COVID-19 infection? Lancet Respir. Med. 2600, 30116 (2020). 
  8. Anderson, L. J. & Schneider, E. Coronaviruses. in Goldman’s Cecil Medicine 2102–2104 (Elsevier, 2012). doi:10.1016/B978-1-4377-1604-7.00374-2. 
  9. Liu, W. et al. Two‐Year Prospective Study of the Humoral Immune Response of Patients with Severe Acute Respiratory Syndrome. J. Infect. Dis. 193, 792–795 (2006). 
  10. Bao, L. et al. Reinfection could not occur in SARS-CoV-2 infected rhesus macaques. bioRxiv 2020.03.13.990226 (2020) doi:10.1101/2020.03.13.990226. 
  11. Ferguson, N. M. et al. Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand. 20 (2020) doi:10.25561/77482.