MLB has faced many challenges in its history, including labor stoppages and wars. Now it faces a global pandemic.The coronavirus stopped the season in the middle of spring training, forcing Opening Day from March to July 23, and the country’s landscape now is no better than it was some months ago. So far, there have been ample numbers of players who have tested positive for the coronavirus and ample numbers of players who likely won’t see the field any time soon. While some have already returned to their teams, that doesn’t mean the aftereffects of the disease won’t play into their lives. Likewise, the pandemic will, indubitably, hurt the sport this year in some form or fashion.MORE: Complete list of MLB players who have opted out of 2020 seasonSo how exactly will players be affected? Does MLB stand a chance at completing its season?Sporting News spoke with Dr. Scott Weisenberg, a clinical associate professor of medicine and director of the Travel Medicine Program at New York University Langone Health. An infectious disease specialist, Weisenberg detailed some of the side effects, potential long-term health effects and MLB’s general plan for playing in 2020.(Editor’s note: Answers have been edited for length and clarity.)SPORTING NEWS: Can you explain what players recovering from a positive COVID-19 test could be dealing with?DR. SCOTT WEISENBERG: So people who have coronavirus can have a range of symptoms, from having no symptoms whatsoever to having very mild symptoms, to having severe symptoms — oftentimes pneumonia-like symptoms with cough, fever — but a lot of other systemic symptoms. For people who have symptoms, in many cases they go on for weeks, and sometimes with some relapse. In the sickest patients those symptoms could go on for months.But, that said, the average outpatient who’s not sick enough to come into the hospital could be sick for a couple days, or they could be sick for a couple weeks. There’s lots of individual variety. Some of them may not have any symptoms at all. The recovery from COVID-19 also varies a lot between individuals. There are some people who are never sick, or better in a couple days. Many people who are sick for one to three weeks, it’s going to take them a while to get their strength back. So, there’s just a lot of individual variation. Someone who’s sick enough to be in the hospital may take over a month or longer to get back into normal health, as far as being able to exercise at their normal rates.But there are others who recover much quicker than that, so it’s all going to be very individual, on a case-to-case basis for those people who are ill enough to end up in a hospital. That would be the sicker proportion of the people will get COVID-19 — there’s lots of people who are not nearly that sick and will recover much faster.SN: Aside from death, what is a worst-case scenario players could face concerning their long-term health?SW: We’re really still learning this. There’s some concern about whether there’s any long-term lung problems, particularly in patients who are sicker or even maybe in patients who are less sick, but this is really still being worked out.There’s a risk with blood clots. Players travel a lot, which is already a prospective for blood clots before you throw in coronavirus. I’m not sure it’s totally worked out with those additive effects, or synergistic effects. So those are the things which would probably be the first things I would think about.Coronavirus can affect somebody’s general energy and maybe exercise tolerance, things like that, but there’s really not enough long-term or short-/medium-term data on that to say how it’s going to affect the average individual, other than what we know from other viral infections.For people who are tired and worn out at the end of infection, like people with mononucleosis, for example, there’s people who are better in a week and there’s people who would take some three months to kind of get back to their normal self. That’s been true with coronavirus as well. There’s certainly individuals who really are not able to get back to their previous exercise routines for a while and there’s others who recover quicker.SN: A COVID-positive player has to test negative twice in a row before returning to play. Is there a lasting threat, even after they test negative, to pass the coronavirus to other teammates?SW: Certainly for outpatients, who are the vast majority of patients, people are most contagious just before they get sick, and for the first couple of days after they get sick.When the CDC (the Centers for Disease Control and Prevention) does symptom-based screening — which is not what Major League Baseball is doing — they use a cutoff of 10 days. In other words, based on the available knowledge, it would be extremely unlikely to transmit the disease once you’ve been sick for several days. Counting 10 days is the cutoff for that.Major League Baseball is doing a test-based clearance system, so they have to do the two negative tests. The idea is: If you have two negative tests, particularly if it’s been more than 10 days, and if somebody wasn’t severely ill in the hospital and receiving medications that impaired their immune system like steroids, then it would be very unlikely for that same person to transmit the disease to other people after 10 days with two negative tests.Again, there are some exceptions for the most sick patients who have received medication to suppress their immune system. That number may go on a little bit longer. The other problem that they will certainly run into is that there are many people who have recovered and are not thought to be contagious, based on the best medical science, but will have positive nasal tests — the PCR tests — that go on for weeks, and sometimes months.There you run into a situation where somebody is probably not contagious. They are recovered, at least as far as acute illness, and yet they are still testing positive. That will certainly occur in some individuals who have a positive test and can’t get cleared to go back (to work) because they keep having positive tests. We see the same problem with people in the hospital and people are trying to go to another facility and need a negative test for that purpose.SN: So, to clarify: For someone who tests positive from a nasal test, there’s no real threat to still pass on the virus to someone else?SW: One of the things I think that there’s a consensus in the medical community is that for people who are in the recovery phase, that a positive test does not mean that you are contagious to other people.The CDC guidelines do have this testing-based policy and they’re being extremely conservative, and of course it’s hard to get to the point where you say it’s 100 percent. There was a study in South Korea, looking at people who were positive more than a month after their original infections, and some of them still even with recurrent symptoms, they couldn’t find any evidence that those individuals transmitted the virus to other people.So these people who have persistently positive PCRs, and are otherwise recovered, are extraordinarily unlikely to pass on the virus to other people.SN: Let’s say a player is exposed to the coronavirus on a day he’s not tested. How quickly would he be able to spread to teammates?SW: This is not entirely clear, but it looks like if you’re exposed today, you’re not going to be positive today. You could get sick anywhere between, say, two days and 14 days from now. For most people it’s about five days.When you first start turning positive — at least in one study — the virus is at lower levels and it peaks over the next day or two. So, basically doing every-other-day testing is a reasonably aggressive approach. So that an individual who is in the incubation stage would very be likely picked up before they transmit to their teammates, or they have a high risk of transmission to teammates.But, since there’s going to be some risk, there’s going to be a possibility somebody tested negative today and they’re positive tomorrow and is not going to get tested again until the next day. That’s where all the social distancing, mask-wearing indoors, all the things that the rest of society should be doing, and Major League Baseball still needs to do.And when you’re outdoors, those risks are not zero but they’re substantially lower. Once someone is on a field, and they have a brief exposure during that day, that’s going to be fairly low-risk.SN: How difficult will it be for MLB players to avoid exposure?SW: As long as there’s widespread disease in the community, it’s going to be very difficult to avoid exposures outside of the baseball realm, and then bringing those back in. Every-other-day testing will hopefully pick those up quickly and avoid transmission within the baseball community. Even if the player is extremely cautious and does not go out, if they have a 14-year-old son goes out and brings that back into the household (then they are exposed). The transmission for this virus are mostly prolonged, close contacts. So household contacts are a major risk.Both the players and everyone in the household has to be extremely cautious about exposures to others, and all those people have to avoid prolonged, close, indoor contact with other people. That’s bars, restaurants, when schools open. It’s just hard to imagine that at some point players are not going to get infected from their household members and community members, and then they’re going to end up testing positive. Hopefully not transmitting to their teammates and other people in the MLB program, but they will certainly have cases.SN: The NBA and MLS are both dealing with bubble situations. Travel increases the risk of contracting the coronavirus. What are your general thoughts on a bubble plan vs. teams traveling in 2020?SW: I think having a bubble gives you a more controllable environment. Like I said, as long as there’s widespread disease in many communities around the United States, other family members, or the players themselves if they do go out, are going to be at risk of picking up the disease from their community and then bringing it back into the baseball community. So it’s really going to depend on what happens everywhere else.Hopefully, we start seeing a decrease in community spread within the next couple of weeks, through all of the progressive public health measures, like what happened in New York. The less disease in the community, the less risk there’s going to be a player’s bringing it back into the baseball community. Otherwise, it will be very difficult. SN: As a doctor in New York City, what would you tell people about the importance of wearing a mask?SW: I don’t blame people (for not wearing masks), because there was so much confusion in the medical community in February and March, and even into April on this issue. But there is no question that the vast majority of the virus transmission for coronavirus is enclosed, prolonged contacts from people who are breathing, talking or coughing.You don’t have to be symptomatic to spread the disease, and wearing a mask reduces the transmission of this virus from person to person. That’s true with different types of masks, including the type we wear in the hospital as well as a cloth mask that are in the community. None of them are perfect, but they all work to reduce transmission significantly. There is no question about that.