Does a positive routine PCR test for Covid-19 virus mean the person is infectious?

Not necessarily! Although a positive routine PCR test for Covid-19 indicates the presence of the virus in a clinical specimen, it does not mean that the virus is still viable or transmissible, particularly as the patient may be recovering from Covid-19. Viral cultures are often needed to help answer this question. 1-5

In a study of 9 hospitalized patients with Covid-19, no viable Covid-19 virus could be found by culture in any specimen beyond 8 days following onset of symptoms despite a positive routine PCR for up to 13 days. Successful growth of the virus was dependent in part on viral load, with samples containing <106 copies/mL never yielding any viable virus.1  

In the same study, none of stools that were positive for Covid-19 virus by PCR were positive by culture.  The authors concluded that there is “little residual risk of infectivity” beyond day 10 of symptoms when sputum contains less than 100,000 viral RNA copies /ml.  Of note, the patients in this study were young- to middle-aged without significant underlying disease and had milder disease, so the results may not necessarily be generalizable to other patients with Covid-19. 1

The discrepancy between a positive PCR and negative culture has been seen with other respiratory pathogens,  such as respiratory syncytial virus (RSV) and influenza. In a study involving experimentally infected subjects with RSV, the average duration of viral shedding was 9.2 days by PCR compared to 7.2 days by viral culture.2 In another study involving patients with symptomatic influenza, virus could be detected for up to 7 days with PCR compared to 1-2 days by viral culture.3

Factors that may explain this discrepancy include suboptimal sample transport, low viral titers,  and the presence of neutralizing antibody in the clinical specimen.2,3

So, despite our incomplete knowledge, don’t assume that PCR positivity means the presence of live virus capable of transmitting Covid-19!

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References

  1. Wolfel R, Corman VM, Guggemos W, et al. Virological assessment of hospitalized patients with COVID-19. Nature 2020; April 1. https://www.nature.com/articles/s41586-020-2196-x
  2. Falsey AR, Formica MA, Treanor JJ, et al. Comparison of quantitative reverse transcriptase-PCR to viral culture for assessment of respiratory syncytial virus shedding. J Clin Microbiol 2003;41:4160-65. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC193781/pdf/0106.pdf
  3. Van Elden LJR, Nijhuis M, Schipper P, et al . Simultaneous detection of influenza viruses A and B using real-time quantitative PCR. J Clin Microbiol 2001;39:196-200. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC87701/
  4. Cangelosi GA, Meschke JS. Dead or alive:molecular assessment of microbial viability. App Environ Microbiol 2014;80:5884-91.
  5. European Centre for Disease Prevention and Control. Novel coronavirus (SARS-CoV-2). https://www.ecdc.europa.eu/en/publications-data/novel-coronavirus-sars-cov-2-discharge-criteria-confirmed-covid-19-cases

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

 

Does a positive routine PCR test for Covid-19 virus mean the person is infectious?

What’s the evidence that people without symptoms can transmit Covid-19 to those around them?

Rapid spread of Covid-19 virus has been attributed in large part to its ease of transmission from person to person even before symptoms develop, particularly since an estimated 18% to 75% of patients testing positive for Covid-19 have no symptoms. 1-4

Transmission before onset of symptoms (presymptomatic): Modeled estimates for the percentage of transmissions that occur from presymptomatic patients range from 37% to as high as 62% based on studies of patients in the cities of Tianjin and Guangzhou in China, as well as Singapore.5-7 Infectiousness appears to begin within 1-3 days prior to symptoms.8-10

Transmission when symptoms never develop (asymptomatic): Asymptomatic transmission was invoked in a familial cluster in Anyang, China where 5 patients developed Covid-19 after a 6th asymptomatic family member returned home from Wuhan, China. The asymptomatic patient never developed symptoms—such as fever or respiratory symptom— and had a normal chest CT, but briefly tested positive for Covid-19 by RT-PCR before testing negative later.11

It’s important to point out that up to ~75% of patients who are initially “asymptomatic” later develop symptoms. 12-14 So what we often call “asymptomatic” may actually be “presymptomatic.”

Transmission of Covid-19 before onset of symptoms is in distinct contrast to SARS, another coronavirus disease, which was transmitted only when a person was symptomatic and was easier to control. This unique property among coronaviruses may be explained by the high tropism of Covid-19 virus not only for the lungs (as in case of SARS virus) but also for the upper respiratory tract.15,16 As such, Covid-19 behaves more like influenza viruses whose upper respiratory tract binding is thought to promote their rapid transmission even before symptoms develop.17  No wonder, Covid-19 spread like wild fire!

 

Coauthor, Bruce Tiu, Harvard Medical Student, Boston, MA

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References

 

  1. Mizumoto K, Kagaya K, Zarebski A, et al. Estimating the asymptomatic proportion of coronavirus diseae 2019 (COID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020. Euro Surveill.2020;25(10):pii=2000180 https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2020.25.10.2000180?ftag=MSF0951a18
  2. Kimaball, A, Hatfield KM, Arons M, et al. Asymptomatic and presymptomatic SARS-CoV-2 infections in residents of a long-term care skilled nursing facility—King County, Washington, March 2020. MMWR 2020;69:377-381. https://www.cdc.gov/mmwr/volumes/69/wr/mm6913e1.htm
  3. Hu Z, Song C, Xu C, et al. Clinical characteristics of 24 asymptomatic infections with COVID-19 screened among close contacts in Nanjing, China. Sci China Life Sci 2020 Mar 4. https://www.ncbi.nlm.nih.gov/pubmed/32146694
  4. Day M. Covid-19: identifying and isolating asymptomatic people helped eliminate virus in Italian village. BMJ 2020;368 https://www.bmj.com/content/368/bmj.m1165
  5. He X, Lau E, Wu P, et al. Temporal dynamics in viral shedding and transmissibility of COVID-19. medRxiv. https://www.medrxiv.org/content/10.1101/2020.03.15.20036707v2
  6. Ferretti L, Wymant C, Kendall M, et al. Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing [published online ahead of print, 2020 Mar 31]. Science. 2020; eabb6936. https://science.sciencemag.org/content/early/2020/03/30/science.abb6936
  7. Ganyani T, Kremer C, Chen D, et al. Estimating the generation interval for COVID-19 based on symptom onset data. medRxiv. https://www.medrxiv.org/content/10.1101/2020.03.05.20031815v1
  8. Wei WE, Li ZB, Chiew CJ, et al. Presymptomatic transmission of SARS-CoV-2 — Singapore, January 23–March 16, 2020. MMWR Morb Mortal Wkly Rep. ePub: 1 April 2020. https://www.cdc.gov/mmwr/volumes/69/wr/mm6914e1.htm
  9. He X, Lau E, Wu P, et al. Temporal dynamics in viral shedding and transmissibility of COVID-19. medRxiv. https://www.medrxiv.org/content/10.1101/2020.03.15.20036707v2
  10. Rothe C, Schunk M, Sothmann P, et al. Transmission of 2019-nCoV Infection from an Asymptomatic Contact in Germany. N Engl J Med. 2020;382(10):970–971. https://www.nejm.org/doi/full/10.1056/NEJMc2001468
  11. Bai Y, Yao L, Wei T, et al. Presumed Asymptomatic Carrier Transmission of COVID-19 [published online ahead of print, 2020 Feb 21]. JAMA. 2020;e202565. https://jamanetwork.com/journals/jama/fullarticle/2762028
  12. Kimball A, Hatfield KM, Arons M, et al. Asymptomatic and Presymptomatic SARS-CoV-2 Infections in Residents of a Long-Term Care Skilled Nursing Facility — King County, Washington, March 2020. MMWR Morb Mortal Wkly Rep. 2020;69:377–381 https://www.cdc.gov/mmwr/volumes/69/wr/mm6913e1.htm
  13. Chen, C. “What We Need to Understand About Asymptomatic Carriers if We’re Going to Beat Coronavirus”. ProPublica. 2020. https://www.propublica.org/article/what-we-need-to-understand-about-asymptomatic-carriers-if-were-going-to-beat-coronavirus
  14. WHO. Report of the WHO-China Joint Mission on Coronavirus Disease 2019 (COVID-19). 2020. https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf
  15. Woelfel R, Corman VM, Guggemos W, et al. Clinical presentation and virological assessment of hospitalized cases of coronavirus disease 2019 in a travel-associated transmission cluster. medRxiv. https://www.medrxiv.org/content/10.1101/2020.03.05.20030502v1
  16. Peiris JS, Chu CM, Cheng VC, et al. Clinical progression and viral load in a community outbreak of coronavirus-associated SARS pneumonia: a prospective study. Lancet. 2003;361(9371):1767–1772. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(03)13412-5/fulltext
  17. van Riel D, den Bakker MA, Leijten LM, et al. Seasonal and pandemic human influenza viruses attach better to human upper respiratory tract epithelium than avian influenza viruses. Am J Pathol. 2010;176(4):1614–1618. https://wwwnc.cdc.gov/eid/article/26/6/20-0357_article

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

What’s the evidence that people without symptoms can transmit Covid-19 to those around them?

Are NSAIDS contraindicated in patients with 2019 novel Coronavirus infection (Covid-19)?

Despite recent internet reports of the association of non-steroidal anti-inflammatory drugs (NSAIDs) with worsening symptoms among patients with Covid-19 (1), firm clinical evidence to support such claims is currently lacking. However, there are some theoretical reasons why it may still be best to avoid NSAIDs in this condition due to their potential adverse impact on the innate and adaptive immune responses as well as their antipyretic properties (2-9).

 
Blunting of the innate immune response: Certain NSAIDs (eg, ibuprofen, naproxen and celecoxib) inhibit cyclooxygenase enzyme-2 (COX-2) and impair production of several pro-inflammatory cytokines important in fighting infections, such as tumor necrosis factor, interleukin 1 and 6, as well as interferon, an antiviral cytokine (2,6,8). COX-2 has been shown to be important in controlling viral replication in influenza (4). Ibuprofen has been associated with inhibitory effects on a variety of polymorphonuclear functions, including chemotaxis (2).

 
Impact on adaptive immune response: COX-2 inhibition may be associated with impaired neutralizing antibody production (3,4,8). Potential mechanisms include modulation of cytokine expression, nitric-oxide production, and antigen processing/presentation and T lymphocyte activation (3,8).

 
Antipyretic effect: NSAIDs are often given for treatment of fever which is an evolutionary host response to infection. A meta-analysis of animal studies evaluating the impact of antipyretics (including aspirin, NSAIDs, and acetaminophen) in influenza found lower survival in animals treated with antipyretics (9). Longer duration of viral shedding has also been associated with the use of aspirin or acetaminophen in rhinovirus infection (9).

 
Formal epidemiologic and experimental studies are sorely needed to evaluate the safety of NSAIDS in Covid-19.  

 

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References
1. Kolata G. Is ibuprofen really risky for Coronavirus patients? NY Times, March 17, 2020. https://www.nytimes.com/2020/03/17/health/coronavirus-ibuprofen.html
2. Graham NMH, Burrell CJ, Douglas RM, et al. Adverse effects of aspirin, acetaminophen and ibuprofen on immune function, viral shedding, and clinical status in rhinovirus-infected volunteers. J Infect Dis 1990;162:1277-1282. https://academic.oup.com/jid/article/162/6/1277/918184
3. Culbreth MJ, Biryunkov S, Shoe JL, et al. The use of analgesics during vaccination with a live attenuated Yersinia pestis vaccine alters the resulting immune response in mice. Vaccines 2019;7, 205; doi:10.3390/vaccines7040205 https://www.mdpi.com/2076-393X/7/4/205
4. Ramos I, Fernandez-Sesma A. Modulating the innate immune response to influenza A virus:potential therapeutic use of anti-inflammatory drugs. Frontiers in Immunology. July 2015. Volume 6. Article 361. https://www.ncbi.nlm.nih.gov/pubmed/26257731
5. Falup-Pecurariu O, Man SC, Neamtu ML, et al. Effects of prophylactic ibuprofen and paracetamol administration on the immunogenicity and reactogenicity of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugated vaccine(PHID-CV) co-administered with DTPa-combined vaccines in children:An open-label, randomized, controlled, non-inferiority trial. Human Vaccines & Immunotherapeutics 2017;13: 649-660. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5360152/
6. Housby JN, Cahill CM, Chu B, et al. Non-steroidal anti-inflammatory drugs inhibit the expression of cytokines and induce HSP70 in human monocytes. Cytokine 1999;11:347-58. https://www.ncbi.nlm.nih.gov/pubmed/30186359
7. Agarwal D, Schmader KE, Kossenkov AV, et al. Immune response to influenza vaccination in the elderly is altered by chronic medication use. Immunity & Ageing 2018;15:19. https://www.ncbi.nlm.nih.gov/pubmed/30186359
8. Bancos S, Bernard MP, Topham DJ, et al. Ibuprofen and other widely used non-steroidal anti-inflammatory drugs inhibit antibody production in human cells. Cell Immunol 2009;258:18-28. https://www.ncbi.nlm.nih.gov/pubmed/19345936
9. Eyers S, Weatherall M, Shirtcliffe P, et al. The effect on mortality of antipyretics in the treatment of influenza infection: systematic review and meta-analysis. J R Soc Med 2010;103:403-11. https://www.ncbi.nlm.nih.gov/pubmed/20929891

 

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

Are NSAIDS contraindicated in patients with 2019 novel Coronavirus infection (Covid-19)?

My previously healthy patient developed a viral illness with fever and headache few days after swimming in a community pool. Can swimming pools be a source of viral infection?

Yes! Swimming pools have been implicated in the transmission of a variety of pathogens,  including enteric viruses (eg, echovirus, coxackie virus, hepatitis A virus, norovirus) which account for nearly one-half of all swimming pool-related outbreaks.  Adenoviruses also account for a significant number of swimming pool outbreaks.1,2

The most commonly reported symptoms in swimming pool outbreaks have been gastroenteritis, respiratory symptoms and conjunctivitis. However, aseptic meningitis and hepatitis may also occur. 1

Because viruses cannot replicate in the environment outside of host tissues, their presence in swimming pool is the result of direct contamination by those in the water who may shed viruses through unintentional fecal release or through body fluids, such as saliva, mucus, or vomitus.  The finding of E. coli in 58% of pool water samples in 1 CDC study suggests the presence of stool as a primary source of infection.3

On average, each person has 0.14 grams (range 0.1 gram to 10 grams) of fecal material on their perianal surface that could rinse into the water if pre-swim shower with soap is omitted.4-5 Coupled with the potential for inadequate disinfection or chlorination of pool water, it is not surprising that swimming pools may serve as a source of infection.  

CDC recommends keeping feces and urine out of the water, checking the chlorine level and pH before getting into the water and not swallowing the water you swim in.3 

Bonus pearl: Did you know that pool water has also been associated with Cryptosporidium and Giardia and waterslides with E.coli-0157 outbreaks?

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References

  1. Bonadonna L, La Rosa G. A review and update on waterborne viral diseases associated with swimming pools. Int j Environ Res Public Health 2019;16, 166. Doi:10.3390/ijerph16020166. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6352248/
  2. Keswick BH, Gebra CP, Goyal SM. Occurrence of enteroviruses in community swimming pools. Am J Public Health 1981;71:1026030. https://www.ncbi.nlm.nih.gov/pubmed/6267950
  3. CDC.Microbes in pool filter backwash as evidence of the need for improved swimmer hygiene—Metro-Atlanta, Georgia, 2012. MMWR 2013;62:385-88. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6219a3.htm
  4. Gerba CP. Assessment of enteric pathogen shedding by bathers during recreational activity and its impact on water quality. Quant Microbiol 2000; 2:55-68 https://arizona.pure.elsevier.com/en/publications/assessment-of-enteric-pathogen-shedding-by-bathers-during-recreat
  5. CDC. Model Aquatic Health Code. 8.0 Annexes: fecal/vomit/blood contamination response Annex (6.0 policies and management), 2008. https://www.cdc.gov/healthywater/pdf/swimming/pools/mahc/structure-content/mahc-fecal-vomit-blood-contamination-response-annex.pdf
  6. CDC. Surveillance of waterborne disease outbreaks and other health events associated with recreational water—United States, 2007-2008 and surveillance of waterborne disease outbreaks associated with drinking water—United States, 2007-2008. MMWR 2011;60. 1-76. https://www.ncbi.nlm.nih.gov/pubmed/21937976

 

 

My previously healthy patient developed a viral illness with fever and headache few days after swimming in a community pool. Can swimming pools be a source of viral infection?

My patient with diabetes mellitus is now admitted with pneumonia. Does diabetes increase the risk of pneumonia requiring hospitalization?

The weight of the evidence to date suggests that diabetes mellitus (DM) does increase the risk of pneumonia-related hospitalization.1-3

A large population-based study involving over 30,000 patients found an adjusted relative risk (RR) of hospitalization with pneumonia of 1.26 (95% C.I 1.2-1.3) among patients with DM compared to non-diabetics.  Of note, the risk of pneumonia-related hospitalization was significantly higher in type 1 as well as type 2 DM and among patients whose A1C level was ≥9.1  Another population-based study found a high prevalence of DM (25.6%) in patients hospitalized with CAP, more than double that in the population studied.2  A 2016 meta-analysis of observational studies also found increased incidence of respiratory tract infections among patients with diabetes (OR 1.35, 95% C.I. 1.3-1.4).

Not only does DM increase the risk of pneumonia-related hospitalization, but it also appears to adversely affect its outcome with increased in-hospital mortality.2 Among patients with type 2 DM,  excess mortality has also been reported at 30 days, 90 days and 1 year following hospitalization for pneumonia. 4,5 More specifically, compared to controls with CAP, 1 year mortality of patients with DM was 30% (vs 17%) in 1 study. 4

Potential reasons for the higher incidence of pneumonia among patients with DM include increased risk of aspiration (eg, in the setting of gastroparesis, decreased cough reflex), impaired immunity (eg, chemotaxis, intracellular killing), pulmonary microangiopathy and coexisting morbidity. 1,3,5,6

Bonus Pearl: Did you know that worldwide DM has reached epidemic levels, such that if DM were a nation, it would surpass the U.S. as the 3rd most populous country! 7

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References

  1. Kornum JB, Thomsen RW, RUS A, et al. Diabetes, glycemic control, and risk of hospitalization with pneumonia. A population-based case-control study. Diabetes Care 2008;31:1541-45. https://www.ncbi.nlm.nih.gov/pubmed/17595354
  2. Martins M, Boavida JM, Raposo JF, et al. Diabetes hinders community-acquired pneumonia outcomes in hospitalized patients. BMJ Open Diabetes Research and Care 2016;4:e000181.doi:10.1136/bmjdrc-2015000181. https://drc.bmj.com/content/4/1/e000181
  3. Abu-Ahour W, Twells L, Valcour J, et al. The association between diabetes mellitus and incident infections: a systematic review and meta-analysis of observational studies. BMJ Open Diabetes Research and Care 2017;5:e000336. https://drc.bmj.com/content/5/1/e000336. 
  4. Falcone M, Tiseo G, Russo A, et al. Hospitalization for pneumonia is associated with decreased 1-year survival in patients with type 2 diabetes. Results from a prospective cohort study. Medicine 2016;95:e2531. https://www.ncbi.nlm.nih.gov/pubmed/26844461
  5. Kornum JB, Thomsen RW, Rus A, et al. Type 2 diabetes and pneumonia outcomes. A population-based cohort study. Diabetes Care 2007;30:2251-57. https://www.ncbi.nlm.nih.gov/pubmed/17595354
  6. Koziel H, Koziel MJ. Pulmonary complications of diabetes mellitus. Pneumonia. Infect Dis Clin North Am 1995;9:65-96. https://www.ncbi.nlm.nih.gov/pubmed/7769221
  7. Zimmet PZ. Diabetes and its drivers: the largest epidemic in human history? Clinical Diabetes and Endocrinology 2017;3:1 https://clindiabetesendo.biomedcentral.com/articles/10.1186/s40842-016-0039-3  

 

My patient with diabetes mellitus is now admitted with pneumonia. Does diabetes increase the risk of pneumonia requiring hospitalization?

My patient with acute exacerbation of heart failure and pulmonary edema also has pneumonia. How often do heart failure and pneumonia coexist?

More often than you might think! The relationship between pneumonia and heart failure (HF) appears bidirectional with pneumonia precipitating heart failure (HF) and HF predisposing to it.

Although It’s often quoted that acute respiratory tract infection accounts for 3-16% of patients hospitalized with decompensated heart failure (HF) (based primarily on small observational studies),1 a 2016 large prospective study involving nearly 100,000 HF admission from 305 US hospitals has reported “pneumonia/respiratory process” as the most common precipitating clinical factor, present in 28.2% of cases (arrhythmia and medication noncompliance came in as 2nd and 3rd).2

Interestingly, the same study reported that pneumonia/respiratory process was most prevalent among patients with preserved (≥50%) ejection fraction (EF) compared to those with borderline ( 40%-49%) or reduced (<40%) EF (33% vs 30% vs 24%, respectively). 2

Pulmonary edema may in turn predispose to bacterial pneumonia through adverse effects of edema fluid on lung bacterial defense mechanisms and establishment of a culture medium for bacterial growth by the presence of fluid in the alveolar space.3

So don’t be surprised if you have to treat for both!

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References

  1. Thomsen RW, Kasatpibal N, Riis A, et al. The impact of pre-existing heart failure on pneumonia prognosis: Population-based cohort study. J Gen Intern Med 2008;23:1407-13. https://www.ncbi.nlm.nih.gov/pubmed/18574639
  2. Kapoor JR, Kapoor R, Ju C, et al. Precipitating clinical factors, heart failure characterization, and outcomes in patients hospitalized with heart failure with reduced, borderline, and preserved ejection fraction. JACC 2016;4:464-72. https://www.scholars.northwestern.edu/en/publications/precipitating-clinical-factors-heart-failure-characterization-and 
  3. Harris GD, Woods DE, Fine R, et al. The effect of intraalveolar fluid on lung bacterial clearance. Lung 1980; 158;91-100 Harris GD, Woods DE, Fine R, et al. The effect of intraalveolar fluid on lung bacterial clearance. Lung 1980; 158;91-100. https://link.springer.com/article/10.1007/BF02713708

 

 

My patient with acute exacerbation of heart failure and pulmonary edema also has pneumonia. How often do heart failure and pneumonia coexist?