Part 2: Coronavirus Histopathology Laboratory Precautions

In the short time since part 1 of this series “Coronavirus in Histology” was published, the COVID-19 virus has continued its spread around the globe. Currently, the entire country of Italy is on lock down. The BBC reports (1) that the Italian government has implemented emergency measures related to the coronavirus outbreak, which include a ban on public gatherings and a travel ban for all residents of the entire country. There are other ramifications occurring around the globe as well.

For us in the United States, it is important to remain calm and pay attention to the science behind the spread of the virus and the precautions used to protect people against infection. This blog will briefly review safety measures that should already be in place in your laboratories which are based on the use of Universal Precautions as detailed by OHSA and the CDC.

The histopathology laboratory receives specimens from clients who treat patients. These patients may not only have coronavirus, but other infectious diseases as well. This is exactly the reason that laboratories must (a) evaluate each laboratory section, and tasks performed, in order to (b) determine what personal protective equipment (PPE) must be used while performing these tasks. What follows are some of the ways in which histology laboratory employees can protect themselves against bacterial and viral agents.

If you work in a reference histopathology laboratory, chances are that all of your specimens arrive to your laboratory in formalin. Formalin is a fixative that will kill and inactivate bacteria and viruses (with the exception of prions, which is a different subject). Still, the specimens that you receive may not be completely fixed when you receive them. This is similar to a hospital histology laboratory which may also receive unfixed specimens.

For this reason, all specimens should be considered infectious at the time of receipt and when undergoing surgical grossing. Based on this information Universal Precautions should be observed. Therefore, when performing the surgical grossing of specimens, any/all of the following personal protective equipment (PPE) should be used: splash proof safety eyewear, face shield, N95 mask, half face respirator (previously fit tested), nitrile disposable gloves, fluid impervious front loading gown with long sleeves, closed toe shoes. All surgical grossing should be performed using a grossing hood, which is operating with a minimum of 100 cubic feet/ minute exhaust air flow. This creates a negative pressure area around the employee, as well as inside the surgical grossing area. The exhaust air must travel to outside of the laboratory area or be passed through HEPA filters prior to being reintroduced into the laboratory.

In the article cited in Part 1 of this series (2), the author stated: “Histopathology laboratories are often fortunate in that routine histotechnology processes often inactivate many viruses, e.g. Ebola [11]… It is, therefore, appropriate to consider that the formalin-fixed paraffin-embedded tissue block would have a low risk of coronavirus infectivity.”
Based on this information, once cassettes are processed and removed from the tissue processor, the specimens may be considered to be non-infectious. However, many laboratories consider it prudent for employees to wear the following PPE when performing embedding, microtomy, staining and coverslipping tasks (even if automated): safety glasses, laboratory coat/ apron and disposable nitrile gloves. Some of these precautions are related to the handling of chemicals and glass (i.e. microscope slides).
But what about possible infection of coronavirus and “regular flu” viruses from co-workers? Laboratories are contained spaces in which many employees may work, both together and on different shifts. The CDC has determined that a cough or sneeze may travel up to 6 fit in any direction, thereby dispersing virus particles which can be inhaled and/or deposited on surfaces. AF Henwood specified in the previous article (2):
“Human-to-human transmissions of the novel coronavirus (2019-nCoV) have been described with incubation times between 2 and 10 days, facilitating its spread via droplets, contaminated hands or surfaces. There may be additional forms of transmission that are yet not determined.”
“Kampf et al. [9] have noted that other coronaviruses, e.g. SARS and MERS, can persist on inanimate surfaces like metal, glass, or plastic for up to 9 days, but can be efficiently inactivated by surface disinfection procedures with 62–71% ethanol, 0.5% hydrogen peroxide, or 0.1% sodium hypochlorite within 1 min.”
It is important to note the “9 day window” of virus particles on surfaces. Histopathology staff that receive specimens in plastic bags, etc. should wear disposable gloves while laying out / opening specimen bags. Personnel who loaded the bags at the patient source may have contaminated the bags during that process.
Additional recent information (3,4) indicates that people infected with COVID-19 “emit high amounts of virus very early on in their infection…”. These same references cite recent studies which suggest that patients with mild coronavirus symptoms can still test positive, by throat swab, for days and weeks after their illness symptoms cease. However, those with mild symptoms are probably not infectious after approximately 10 days after their symptoms become noticeable. Also, a Johns Hopkins University’s Bloomberg School of Public Health found that the coronavirus “has an incubation period of 14 days with people showing symptoms an average of five days after catching it.”.
So…. What to do in your histopathology laboratory with regard to “person to person” transmission?
1. Follow the CDC recommendations for vigorous hand washing with soap and hot water for at least 20 seconds. If not available, then use alcohol based hand sanitizers (i.e. containing at least 60% alcohol). Perform hand washing throughout the day, before and after using gloves, handling equipment, working on benchtops and upon entering and leaving the laboratory.

2. Clean and sanitize work surfaces, door handles, workstations, etc. with “62 – 71% ethanol, or 0.1% sodium hypochlorite (i.e. bleach) solutions” (2). As noted above, the corona viruses can remain viable on surfaces for up to 9 days.

3. If you are experiencing any flu-like symptoms (i.e. coughing, sneezing, fever, shortness of breath, headache, etc.) – stay home. Coming in to work while sick is a sure way to spread whatever it is that you have to others. This keeps the infection alive and moving from person to person. Also, resting at home and staying hydrated will help you to recover from your illness more quickly.

4. When you are healthy, you only need to wear a mask if you are taking care of a person with suspected COVID-19 infection. A mask does not filter out virus particles – they are too small. However, it will prevent sneeze / cough droplets from entering your nose and mouth. A sick person should wear a mask if they are coughing or sneezing, to prevent their cough/ sneeze droplets from spreading to healthy people.

5. At home, prepare for a community wide outbreak. You should have food and other essentials to last you for at least two weeks.

Readers are encouraged to review their Bloodborne Pathogens program, including measures pertaining to Universal Precautions, to ensure their safety in a histopathology laboratory. By adhering to hand washing procedures and appropriate use of PPE, histopathology employees are better able to protect themselves from infection with the COVID-19 virus.


  • Henwood AF. Coronavirus disinfection in histopathology.
    Published online: 01 Mar 2020, Journal of Histotechnology
    Helen Branswell, author, 3-9-2020.
    Gander, author, 3-9-20.
  • Chapman CM. The Histology Handbook. Amazon CreateSpace Independent Publishing Platform; 2017.
  • Chapman CM, Dimenstein IB. Dermatopathology Laboratory Techniques. Amazon CreateSpace Independent Publishing Platform; 2016.