By Liz Highleyman

Hepatitis C virus (HCV) is most efficiently transmitted through direct blood exposures, for example, sharing needles for drug injection or needle-stick accidents in a healthcare setting. Various other routes of transmission are possible, not all of which are well characterized or confirmed. In up to 20% of hepatitis C cases, the transmission route is unknown.

Study findings reported in the October 1, 2008 issue of Clinical Infectious Diseases add to the evidence that HCV may transmitted via nasal membranes when using shared straws or bills to snort drugs. This may happen because prolonged intranasal drug use can erode the delicate mucous membranes and cause bleeding. Some epidemiological studies have demonstrated a link between intranasal drug use and HCV infection, but results have been inconsistent.

In the present study, the investigators measured the presence of blood and HCV RNA in nasal secretions and on drug-sniffing implements collected from 38 drug-using clients with active chronic hepatitis C recruited at a community health clinic in East Harlem, New York City. Participants' HCV viral loads ranged from 250 to 5,000,000 copies/mL (median, 5000 copies/mL). About one-third were coinfected with HIV and 45% also had hepatitis B.

Participants provided swabs of nasal secretions, their nasal membranes were examined for damage, and they "snorted air" through plastic soda straws that were then tested.

Results

• Trace amounts of blood were detected in 28 of 38 nasal secretion samples (74%).

• However, blood was detected on just 3 of the 38% straws (8%).

• HCV RNA was detected in 5 of 38 nasal secretion samples (13%)

• HCV was also detected on 2 of 38 straws (5%).

• 2 nasal swab samples harbored HCV despite lack of detectable blood.

• Conversely, 3 samples containing traces of blood had no detectable HCV.

• Nasal symptoms associated with chronic intranasal drug use were common:

• 71% of the participants had evidence of rhinitis (nasal inflammation).

• More than 40% reported runny nose or nasal congestion at least once per week.

• 16% had symptoms of saddle-nose (collapse of the nasal bridge).

• 11% had perforations of the nasal septum separating the nostrils.

• 8% reported lesions of the nasal mucous membranes.

• 8% reported nose bleeds at least once per week.

"We demonstrate the virological plausibility of intranasal transmission by confirming that blood and HCV RNA are present in the nasal secretions and drug-sniffing implements of HCV-infected intranasal drug users," the study authors wrote.

"Our findings revealed a high prevalence of blood (74%) in the nasal secretions of HCV-positive long-term drug sniffers," they elaborated in their discussion. "We also confirmed that HCV RNA was present in the nasal secretions of a substantial proportion (13%) of this cohort. Most significantly, this study demonstrated that both blood and HCV particles can be transferred onto sniffing implements (i.e., straws) during simulated intranasal drug use."

Prior studies have shown that HCV can live on surfaces for up to 16 hours, but it is not known how much virus is required for transmission.

The authors suggested that their estimates are likely conservative, since "[i]t is reasonable to assume that HCV will be present in the nasal secretions with greater frequency and quantity during episodes of active drug sniffing, which may exacerbate discharge of nasal fluids and blood."

"[T]hese findings lend important virological and clinical support to the intranasal HCV transmission hypothesis," they concluded. "In addition, detection of HCV in nasal secretions advances the debate regarding potential iatrogenic and nosocomial transmission of HCV in the context of ear, nose, and throat and related clinical practices. More research is needed to confirm intranasal transmission as a mode of viral infection and to determine its impact on the wider epidemic of HCV infection."

St. Luke's-Roosevelt Institute for Health Sciences, Columbia University, New York, NY; National Development and Research Institutes, New York, NY; Boriken Neighborhood Health Center, New York, NY ; Beth Israel Medical Center, New York, NY; School of Nursing, University of Rochester Medical Center, Rochester, NY; School of Public Health, Louisiana State University, New Orleans, LA; School of Public Health, Center for Global Health Research, University of Puerto Rico, San Juan, PR.

9/19/08

Reference
A Sagiv, JM McMahon, D Milano, and others. Intranasal transmission of hepatitis C virus: virological and clinical evidence. Clinical Infectious Diseases 47(7): 931-934. October 1, 2008. (Abstract).